Patent Publication Number: US-9410180-B2

Title: Biological sterilization indicator system and method

Description:
FIELD 
     The present disclosure generally relates to sterilization indicator systems and methods, and particularly, to biological sterilization indicator systems and methods. 
     BACKGROUND 
     In a variety of industries, such as the health care industry but also in other industrial applications, it can be necessary to monitor the effectiveness of processes used to sterilize equipment such as medical devices, instruments and other disposable and non-disposable articles. In these settings, sterilization is generally defined as the process of completely destroying all viable sources of biological activity, such as microorganisms, including structures such as viruses and spores. As a standard practice, hospitals include a sterility indicator with a batch of articles to assay the lethality of the sterilization process. Both biological and chemical sterility indicators have been used. 
     One standard type of biological sterility indicator includes a known quantity of test microorganisms, for example  Geobacillus stearothermophilus  (formerly  Bacillus stearothermophilus ) or  Bacillus atrophaeus  (formerly  Bacillus subtilis ) spores, which can be many times more resistant to particular sterilization processes than other contaminating organisms. After the indicator is exposed to the sterilization process, the sources of biological activity (e.g., spores) can be incubated in a nutrient medium to determine whether any of the sources survived the sterilization process, with source metabolism and/or growth indicating that the sterilization process was insufficient to destroy all of the sources of biological activity. 
     Available chemical sterility indicators can be read immediately at the end of the sterilization process. However, the results indicate only that a particular condition was present during the sterilization process, such as the presence of a particular chemical or a temperature, and potentially, that the condition was reached for a certain period of time. On the contrary, the response of sources of biological activity to all conditions actually present can be a more direct and reliable test for how effective a sterilization process is in achieving sterilization. 
     SUMMARY 
     Some aspects of the present disclosure provide a biological sterilization indicator system. The system can include a biological sterilization indicator and a reading apparatus. The biological sterilization indicator can include a housing including a first portion, and a second portion adapted to be coupled to the first portion, the second portion being movable with respect to the first portion, when coupled to the first portion, between a first position and a second position. The biological sterilization indicator can further include a container containing a liquid and being dimensioned to be positioned in the housing. At least a portion of the container can be frangible, and the container can be positioned in at least the first portion of the housing. The container can have a first state in which the container is intact when the second portion of the housing is in the first position, and a second state in which the container is fractured when the second portion of the housing is in the second position. The reading apparatus can include a well. The well can be dimensioned to receive at least a portion of the biological sterilization indicator, and the reading apparatus configured to detect at least one of the following conditions: (i) when the well is empty; (ii) when the biological sterilization indicator is positioned in the well with the second portion of the housing in the first position; and (iii) when the biological sterilization indicator is positioned in the well with the second portion of the housing in the second position. 
     Some aspects of the present disclosure provide a method for detecting an activation status of a biological sterilization indicator. The method can include providing a biological sterilization indicator and a reading apparatus. The biological sterilization indicator can include a housing including a first portion, and a second portion adapted to be coupled to the first portion, the second portion being movable with respect to the first portion between a first position and a second position. The biological sterilization indicator can further include a container containing a liquid. At least a portion of the container can be frangible, and the container can be positioned in at least the first portion of the housing. The container can have a first state in which the container is intact when the second portion of the housing is in the first position, and a second state in which the container is fractured when the second portion of the housing is in the second position. The reading apparatus can include a well dimensioned to receive at least a portion of the biological sterilization indicator. The method can further include detecting at least one of the following conditions: (i) when the well is empty; (ii) when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the first position, and (iii) when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the second position. 
     Some aspects of the present disclosure provide a biological sterilization indicator system. The system can include a biological sterilization indicator and a reading apparatus. The biological sterilization indicator can include a housing, which can include a first portion, and a second portion adapted to be coupled to the first portion. The second portion can be movable with respect to the first portion (e.g., when coupled to the first portion) between a first position and a second position. The biological sterilization indicator can further include a container containing a liquid and dimensioned to be positioned in the housing. At least a portion of the container can be frangible, and the container can be positioned in at least the first portion of the housing. The container can have a first state in which the container is intact when the second portion of the housing is in the first position, and a second state in which the container is fractured when the second portion of the housing is in the second position. The reading apparatus can include at least one well. The well can be dimensioned to receive at least a portion of the biological sterilization indicator. The reading apparatus can be adapted to generate at least one of a first signal indicative of the well being empty; a second signal indicative of the biological sterilization indicator being positioned in the well with the second portion of the housing in the first position; and a third signal indicative of the biological sterilization indicator being positioned in the well with the second portion of the housing in the second position. 
     Some aspects of the present disclosure provide a method for detecting an activation status of a biological sterilization indicator. The method can include providing a biological sterilization indicator and a reading apparatus. The biological sterilization indicator can include a housing, which can include a first portion, and a second portion adapted to be coupled to the first portion. The second portion can be movable with respect to the first portion (e.g., when coupled to the first portion) between a first position and a second position. The biological sterilization indicator can further include a container containing a liquid. At least a portion of the container can be frangible, and the container can be positioned in at least the first portion of the housing. The container can have a first state in which the container is intact when the second portion of the housing is in the first position, and a second state in which the container is fractured when the second portion of the housing is in the second position. The reading apparatus can include a well dimensioned to receive at least a portion of the biological sterilization indicator. The method can further include generating a first signal when the well is empty, and positioning the biological sterilization indicator in the well of the reading apparatus and generating at least one of the following signals: a second signal when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the first position; and a third signal when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the second position. 
     Other features and aspects of the present disclosure will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a biological sterilization indicator system according to one embodiment of the present disclosure, the biological sterilization indicator system comprising at least one biological sterilization indicator positioned in a reading apparatus. 
         FIG. 2  is an exploded perspective view of a biological sterilization indicator of  FIG. 1 , the biological sterilization indicator including a housing comprising a first portion and a second portion. 
         FIG. 3  is a cross-sectional side view of the biological sterilization indicator system of  FIG. 1 , taken along line  3 - 3  of  FIG. 1 , the biological sterilization indicator shown in a first state, and the second portion of the housing of the biological sterilization indicator shown in a first position. 
         FIG. 4  is a cross-sectional side view of the biological sterilization indicator system of  FIGS. 1-3 , the biological sterilization indicator system shown in a second state, and the second portion of the housing of the biological sterilization indicator shown in a second position. 
         FIG. 5  is a schematic block diagram of the reading apparatus of  FIG. 1 . 
         FIG. 6  is a perspective view of a second portion of the housing of the biological sterilization indicator according to another embodiment of the present disclosure. 
         FIG. 7  is a perspective view of a second portion of the housing of the biological sterilization indicator according to another embodiment of the present disclosure. 
         FIG. 8  is a perspective view of a second portion of the housing of the biological sterilization indicator according to another embodiment of the present disclosure. 
         FIG. 9  is a perspective view of a biological sterilization indicator according to another embodiment of the present disclosure. 
         FIG. 10  is a partial cross-sectional side view of a biological sterilization indicator system according to another embodiment of the present disclosure, the biological sterilization indicator system including a biological sterilization indicator shown in a perspective view. 
         FIG. 11  is a top cross-sectional view of a portion of the reading apparatus of  FIGS. 1-5 , taken along the line  11 - 11  shown in  FIG. 3 , with portions removed for clarity, and with objects beyond the plane defined by the line  11 - 11  removed for clarity. 
         FIG. 12  is a front cross-sectional view of a portion of the reading apparatus of  FIGS. 1-5 , taken along the line  12 - 12  shown  FIG. 1 , with portions removed for clarity, and with objects beyond the plane defined by the line  12 - 12  removed for clarity. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the present disclosure are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. It is to be understood that other embodiments may be utilized, and structural or logical changes may be made without departing from the scope of the present disclosure. Furthermore, terms such as “front,” “rear,” “top,” “bottom,” and the like are only used to describe elements as they relate to one another, but are in no way meant to recite specific orientations of the apparatus, to indicate or imply necessary or required orientations of the apparatus, or to specify how the invention described herein will be used, mounted, displayed, or positioned in use. 
     The present disclosure generally relates to biological sterilization indicator systems and methods. A biological sterilization indicator is also sometimes referred to as a “biological sterility indicator,” or simply, a “biological indicator.” Some embodiments of the biological sterilization indicator systems and methods of the present disclosure include self-contained biological sterilization indicators that can be used to determine the lethality of a sterilizing process. A system can include the biological sterilization indicator as well as a reading apparatus or detector configured to assay the biological sterilization indicator and inform a user (e.g., visually, aurally, etc.) of the lethality of the sterilization process. 
     Pressurized steam or other common sterilants can be used to sterilize equipment and supplies used in healthcare environments. Small, self-contained indicators, such as biological sterilization indicators, can be used to verify the efficacy of the sterilization processes. These indicators can be biological and can contain sources of biological activity. 
     Nutrient medium used to nourish the sources of biological activity (e.g., spores) following a sterilization procedure can be present throughout the sterilization procedure but may not be accessible by the sources of biological activity until desired. For example, a frangible pouch or container (e.g., an ampoule, such as a glass ampoule) can house the medium ‘on board’ separately from the sources of biological activity, and the container can be fractured to put the sources of biological activity and medium in fluid communication with one another, when desired (e.g., after a sterilization process). Nutrients and nutrient media to facilitate the growth of microorganisms are known in the art and can be found, for example, in the “Handbook of Microbiological Media” by Ronald Atlas, published by CRC Press, Boca Raton, Fla. Matner et al. (U.S. Pat. No. 5,073,488), which is incorporated herein by reference in its entirety, describes a nutrient medium for the growth and detection of bacterial spores in a biological sterilization indicator that can be employed in biological sterilization indicators of the present disclosure. 
     Generally, sources of biological activity (e.g., microorganisms) are chosen to be used in a biological sterilization indicator that are resistant to a particular sterilization process. The biological sterilization indicators of the present disclosure include a viable quantity, or culture, of one or more known sources of biological activity (e.g., species of microorganism). Such sources of biological activity can be in the form of microbial spores. The test source in the biological sterilization indicator is either killed by a successful sterilization cycle, or survives if the sterilization cycle is not adequate for some reason. Bacterial spores, rather than the vegetative form of the organisms, are sometimes used at least partly because vegetative bacteria are known to be relatively easily killed by sterilizing processes. Spores can also have superior storage characteristics and can remain in their dormant state for years. As a result, in some embodiments, sterilization of an inoculum of a standardized spore strain can provide a high degree of confidence that inactivation of all microorganisms in a sterilizing chamber has occurred. 
     By way of example only, the present disclosure describes the one or more sources of biological activity used in the biological sterilization indicator as being “spores;” however, it should be understood that the type of source (e.g., spore) used in a particular embodiment of the biological sterilization indicator is selected for being highly resistant to the particular sterilization process contemplated. Accordingly, different embodiments of the present disclosure may use different sources of biological activity, depending on the sterilization process for which the particular embodiment is intended. The term “spores” is used throughout the present disclosure for simplicity, but it should be understood that other sources of biological activity, such as microorganisms (e.g., bacteria, fungi, viruses, etc.), spores (e.g., bacterial, fungal, etc.), enzymes, substrates for enzymatic activity, ATP, microbial metabolites, or a combination thereof, can be used in the biological sterilization indicator of the present disclosure instead. 
     The phrase “biological activity” generally refers to any specific catalytic process or groups of processes associated with a biological cell. Nonlimiting examples of biological activities include catabolic enzyme activities (e.g., carbohydrate fermentation pathways), anabolic enzyme activities (e.g., nucleic acid, amino acid, or protein synthesis), coupled reactions (e.g., a metabolic pathway), biomolecule-mediated redox reactions (e.g., electron transport systems), and bioluminescent reactions. “Predetermined” biological activity means that the method is directed toward the detection of a specific biological process (e.g., an enzyme reaction) or group of biological processes (e.g., a biochemical pathway). It will be appreciated by a person having ordinary skill in the art that certain predetermined biological activities may be associated with a particular type of cell (e.g., cancer cell or microorganism) or a pathological process. 
     Similarly, it should be understood that phrases used in the present disclosure that include the term “spore,” such as “spore carrier,” “spore reservoir,” “spore region,” “spore growth chamber,” and the like, are used merely for simplicity, but that such components, elements or phrases equally apply to other sources of biological activity and are not intended to refer only to spores. For example, the above phrases can also be referred to as a “source carrier,” a “source region,” a “source reservoir,” a “source growth chamber,” and the like. 
     The process of bringing the spores and medium together can be referred to as “activation” of the biological sterilization indicator. That is, the term “activation” and variations thereof, when used with respect to a biological sterilization indicator, can generally refer to bringing spores of the biological sterilization indicator in fluid communication with a liquid or medium (e.g., an aqueous mixture comprising a nutrient medium for the spores). For example, when a frangible container within the biological sterilization indicator that contains the medium is at least partially fractured, punctured, pierced, crushed, cracked, or the like, such that the medium has been put in fluid communication with the spores, the biological sterilization indicator can be described as having been “activated.” Said another way, a biological sterilization indicator has been activated when the spores have been exposed to the medium which was previously housed separately from the spores. 
     After a biological sterilization indicator has been exposed to a sterilization cycle, the sterilization load (e.g., including the items desired to be sterilized and the biological sterilization indicator) can be removed from the sterilizer. One of the first steps in processing the biological sterilization indicator can include activating the biological sterilization indicator. In some embodiments, activation can include closing the biological sterilization indicator, which can include moving a portion (e.g., a cap) of the biological sterilization indicator relative to another portion of the biological sterilization indicator (e.g., a tube, a base, a tubular body, etc.). In some embodiments, the interior of the biological sterilization indicator can remain in fluid communication with ambience during sterilization, but closed off from ambience after sterilization. For example, in some embodiments, the cap of the biological sterilization indicator can be coupled to the tube of the biological sterilization indicator during sterilization in a first position that maintains fluid communication between the interior of the biological sterilization indicator and ambience. After sterilization, the cap can be pressed further onto the tube (e.g., to a second position in which the interior of the biological sterilization indicator is no longer in fluid communication with ambience) to maintain sterility and reduce the evaporation rate of a medium (e.g., a liquid) used to support the metabolic activity and/or growth of the spores (i.e., if still viable). The medium can be contained during sterilization and released into the interior of the biological sterilization indicator after sterilization. For example, the medium can be separately housed from the spores during sterilization in a frangible container that can be at least partially fractured after sterilization (e.g., in response to moving the cap relative to the tube or base of the biological sterilization indicator) to bring the medium into fluid communication with the spores to ensure proper nutrition of the spores. 
     In some embodiments of the present disclosure, closing the biological sterilization indicator (e.g., moving a portion relative to another portion to seal the interior) can include or cause fracturing of a frangible container containing the medium, such that closing the biological sterilization indicator causes activation of the biological sterilization indicator. 
     The present disclosure generally relates further to systems and methods for determining whether a portion of the biological sterilization indicator has been moved a sufficient amount relative to another portion of the biological sterilization indicator, for example, to indicate that the biological sterilization indicator has been “activated.” That is, some embodiments of the systems and methods of the present disclosure can be used to detect and/or confirm “cap closure.” Still, in some embodiments, the systems and methods of the present disclosure can be used to detect whether the biological sterilization indicator has been activated and the medium and spores are in fluid communication with one another. For example, in some embodiments, the position of the cap of the biological sterilization indicator relative to another portion of the biological sterilization indicator can be detected to determine whether the frangible container is intact or broken, and such information can indicate whether the medium and the spores are in fluid communication with one another. As a result, some embodiments of the present disclosure can reliably assay the position of one portion of the biological sterilization indicator relative to another portion to determine whether the biological sterilization indicator has been activated. In some embodiments, alternatively or additionally, activation of the biological sterilization indicator can be confirmed by detecting the presence of liquid (e.g., growth medium) in a specific chamber (e.g., a spore growth chamber or detection chamber) of the biological sterilization indicator. Such liquid or fluid detection is described in greater detail in co-pending U.S. Application No. 61/408,997, filed Nov. 1, 2010, entitled “Biological Sterilization Indicator System and Method,” which is incorporated herein by reference in its entirety. 
     Confirmation of the activation of the biological sterilization indicator can be important, because if the liquid or medium is not made available to the spores, the biological sterilization indicator may not function properly, which may compromise the efficacy result of a given sterilization process. 
     The biological sterilization indicator of the present disclosure can be used with a variety of sterilization processes including, but not limited to, exposure to steam (e.g., pressurized steam), dry heat, gaseous or liquid agents (e.g., ethylene oxide, hydrogen peroxide, peracetic acid, ozone, or combinations thereof), radiation, or combinations thereof. In at least some of the sterilization processes, an elevated temperature, for example, 50° C., 100° C., 121° C., 132° C., 134° C., or the like, is included or may be encountered in the process. In addition, elevated pressures and/or a vacuum may be encountered, for example, 15 psi (1×10 5  Pa) 
     The spores used in a particular system are selected according to the sterilization process used. For example, for a steam sterilization process,  Geobacillus stearothermophilus  or  Bacillus stearothermophilus  can be used. In another example, for an ethylene oxide sterilization process,  Bacillus atrophaeus  (formerly  Bacillus subtilis ) can be used. In some embodiments, the sterilization process resistant spores can include, but are not limited to, at least one of  Geobacillus stearothermophilus, Bacillus stearothermophilus, Bacillus subtilis, Bacillus atrophaeus, Bacillus megaterium, Bacillus coagulans, Clostridium sporogenes, Bacillus pumilus , or combinations thereof. 
     Enzymes and substrates that can be suitable for use in the biological sterilization indicator of the present disclosure are identified in U.S. Pat. Nos. 5,073,488 (Matner et al), 5,418,167 (Matner et al.), and 5,223,401 (Foltz et al.), which are incorporated herein by reference for all they disclose. 
     Suitable enzymes can include hydrolytic enzymes and/or enzymes derived from spore-forming microorganisms, such as  Bacillus stearothermophilus  and  Bacillus subtilis . Enzymes from spore-forming microorganisms that can be useful in the biological sterilization indicators of the present disclosure can include beta-D-glucosidase, alpha-D-glucosidase, alkaline phosphatase, acid phosphatase, butyrate esterase, caprylate esterase lipase, myristate lipase, leucine aminopeptidase, valine aminopeptidase, chymotrypsin, phosphohydrolase, alpha-D-galactosidase, beta-D-galactosidase, tyrosine aminopeptidase, phenylalanine aminopeptidase, beta-D-glucuronidase, alpha-L-arabinofuranosidase, N-acetyl-beta-glucosaminodase, beta-D-cellobiosidase, alanine aminopeptidase, proline aminopeptidase and fatty acid esterases. 
     Some embodiments of the biological sterilization indicator can include chromogenic and/or fluorogenic substrates that react with enzymes to form detectable products (M. Roth,  Methods of Biochemical Analysis , Vol. 17, D. Block, Ed., Interscience Publishers, New York, 1969, p. 89, incorporated herein by reference; S. Udenfriend,  Fluorescence Assay in Biology and Medicine , Academic Press, New York, 1962, p. 312; and D. J. R. Lawrence,  Fluorescence Techniques for the Enzymologist , Methods in Enzymology, Vol. 4, S. P. Colowick and N. O. Kaplan, Eds., Academic Press, New York, 1957, p. 174). These substrates may be classified in two groups based on the manner in which they create a visually detectable signal. The substrates in the first group react with enzymes to form enzyme-modified products that are themselves chromogenic or fluorescent. Substrates in the second group form enzyme-modified products that must react further with an additional compound, or compounds, to generate a color or fluorescent signal. 
     As a result, the phrase “detectable product” can refer to any molecule, compound, substance, substrate, or the like, or combinations thereof, that can be detected by any of the detection methods or processes described below. For example, such detectable products can be a sign of the viability of a source of biological activity, and detection of such products can generally indicate the failure or inadequacy of a sterilization process. 
     In some embodiments, the source of active enzyme can be (1) the purified, isolated enzyme derived from an appropriate microorganism; (2) a microorganism to which the enzyme is indigenous or added by genetic engineering; and/or (3) a microorganism to which the enzyme has been added during sporulation or growth, such that the enzyme is incorporated or associated with the microorganism, e.g., an enzyme added to a spore during sporulation which becomes incorporated within the spore. In some embodiments, the microorganisms which may be utilized as the source of an enzyme include bacteria or fungi in either the spore or vegetative state. In some embodiments, the enzyme source includes  Bacillus, Clostridium, Neurospora, Candida , or a combination of such species of microorganisms. 
     The enzyme alpha-D-glucosidase has been identified in spores of  Bacillus stearothermophilus , such as those commercially available as “ATCC 8005” and “ATCC 7953” from American Type Culture Collection, Rockville, Md. The enzyme beta-D-glucosidase has been found in  B. subtilis  (e.g., commercially available as “ATCC 9372” from American Type Culture Collection). 
     In the event that an isolated enzyme is utilized, or the microorganism used as the source of the enzyme is not more resistant to the sterilization conditions than the natural contaminants, another microorganism commonly used to monitor sterilization conditions can be exposed to the sterilization cycle along with the enzyme source. In such a case, the method of the present disclosure may include the step of incubating any viable microorganism remaining after the sterilization cycle with an aqueous nutrient medium to confirm the sterilization efficacy. 
     In general, monitoring the effectiveness of the sterilization process can include placing the biological sterilization indicator of the present disclosure in a sterilizer. In some embodiments, the sterilizer includes a sterilization chamber that can be sized to accommodate a plurality of articles to be sterilized, and can be equipped with a means of evacuating air and/or other gases from the chamber and a means for adding a sterilant to the chamber. The biological sterilization indicator of the present disclosure can be positioned in areas of the sterilizer that are most difficult to sterilize (e.g., above the drain). Alternately, the biological sterilization indicator of the present disclosure can be positioned adjacent (or in the general proximity of) an article to be sterilized when the biological sterilization indicator is positioned in the sterilization chamber. In addition, the biological sterilization indicator can be positioned in process challenge devices that can be used in sterilizers. 
     The sterilization process can further include exposing the article(s) to be sterilized and the biological sterilization indicator to a sterilant. In some embodiments, the sterilant can be added to the sterilization chamber after evacuating the chamber of at least a portion of any air or other gas present in the chamber. Alternatively, sterilant can be added to the chamber without evacuating the chamber. A series of evacuation steps can be used to assure that the sterilant reaches all desired areas within the chamber and contacts all desired article(s) to be sterilized, including the biological sterilization indicator. 
     In general, after the biological sterilization indicator has been exposed to a sterilization cycle, a liquid (e.g., a growth media, water that can be mixed with a solid growth media, etc., or combinations thereof) can be introduced to the spores. As mentioned above, the step in which the liquid is introduced to the spores can be referred to the “activation step.” If the spores have survived the sterilization cycle, the liquid will facilitate metabolic activity and/or growth of the spores, and such activity and/or growth can be investigated. If growth is observed, the sterilization cycle is generally deemed ineffective. 
       FIGS. 1-4  illustrate a biological sterilization indicator system  10  according to one embodiment of the present disclosure. The biological sterilization indicator system  10  includes a reading apparatus  12  (also sometimes referred to as a “detector”, a “reader,” an “assaying device”, or the like) and one or more biological sterilization indicators  100 . Particularly, as shown in  FIG. 1 , the reading apparatus  12  can include one or more wells or recesses  14 . Each well  14  can be dimensioned to receive at least a portion of a biological sterilization indicator  100 . Each well  14  can have any desired shape, size or configuration necessary to hold and/or retain at least a portion of a biological sterilization indicator  100 . In some embodiments, as shown in  FIG. 1 , each well  14  of the reading apparatus  12  can be dimensioned to receive one biological sterilization indicator  100 , and each well  14  can be configured to assay, and output results for, one biological sterilization indicator  100  at a time. Examples of various features that may be employed in the reading apparatus  12  are described in U.S. Pat. No. 6,025,189 (Bolea et al.), which is incorporated herein by reference. 
     As further shown in  FIG. 1 , the reading apparatus  12  can further include a display and/or user interface  16 , which can visually display various outputs from the reading apparatus  12  and/or which can receive input from a user (e.g., via a multi-button membrane switch). Various outputs that can be displayed can include, but are not limited to, errors or error codes, assay or lethality results, the presence of a biological sterilization indicator  100  in a given well  14 , other suitable outputs, or combinations thereof. In some embodiments, as shown in  FIG. 1 , the reading apparatus  12  can include a front face  18  that includes the display and/or user interface  16  and which can be angled to facilitate access to the wells  14  and/or to facilitate viewing the display  16 , or other items on the face  18 . Furthermore, in some embodiments, the reading apparatus  12  can include a substantially horizontal or flat top wall  20  that can facilitate stacking of multiple reading apparatuses  12  on top of one another, such that multiple reading apparatuses  12  can be operated and read simultaneously, as desired. The reading apparatus  12  and operation of the biological sterilization indicator system  10  will be described in greater detail below, with reference to  FIGS. 3-5 . First, the biological sterilization indicator  100  will be described in detail, with reference to  FIGS. 2-4 . 
     Biological Sterilization Indicator 
       FIGS. 2-4  illustrate the biological sterilization indicator  100  in greater detail. Other suitable embodiments of biological sterilization indicators are described in co-pending PCT Patent Application No. PCT/US2010/041010, entitled “Biological Sterilization Indicator and Method of Using Same” (Docket No. 65578WO003); U.S. Patent Application No. 61/408,997, entitled “Biological Sterilization Indicator System and Method”, U.S. Patent Application No. 61/408,988, entitled “Biological Sterilization Indicator and Method of Using Same”; and U.S. Patent Application No. 61/408,977, entitled “Biological Sterilization Indicator”; each of which is incorporated herein by reference in its entirety. 
     The biological sterilization indicator  100  can include a housing  102 , which can include a first portion  104  and a second portion  106  (e.g., a cap) adapted to be coupled together to provide a self-contained biological sterilization indicator. In some embodiments, the first portion  104  and second portion  106  can be formed of the same materials, and in some embodiments, the first portion  104  and the second portion  106  can be formed of different materials. The housing  102  can define a reservoir  103  of the biological sterilization indicator  100  in which other components can be positioned and into which a sterilant can be directed during a sterilization process. 
     The housing  102  can be defined by at least one liquid impermeable wall, such as a wall  108  of the first portion  104  and/or a wall  110  of the second portion  106 . It should be understood that a one-part unitary housing  102  may also be employed or that the first and second portions  104  and  106  can take on other shapes, dimensions, or relative structures without departing from the spirit and scope of the present disclosure. Suitable materials for the housing  102  (e.g., the walls  108  and  110 ) can include, but are not limited to, a glass, a metal (e.g., foil), a polymer (e.g., polycarbonate (PC), polypropylene (PP), polyphenylene (PPE), polythyene, polystyrene (PS), polyester (e.g., polyethylene terephthalate (PET)), polymethyl methacrylate (PMMA or acrylic), acrylonitrile butadiene styrene (ABS), cyclo olefin polymer (COP), cyclo olefin copolymer (COC), polysulfone (PSU), polyethersulfone (PES), polyetherimide (PEI), polybutyleneterephthalate (PBT)), a ceramic, a porcelain, or combinations thereof. 
     In some embodiments, the biological sterilization indicator  100  can further include a frangible container  120  that contains a liquid (e.g., an aqueous mixture)  122 , and which is dimensioned to be received within the biological sterilization indicator  100 , for example, within at least a portion of the housing  102  (e.g., at least within the first portion  104  of the housing  102 ). The frangible container  120  can be formed of a variety of materials, including, but not limited to, one or more of metal (e.g., foil), a polymer (e.g., any of the polymers listed above with respect to the housing  102 ), glass (e.g., a glass ampoule), and combinations thereof. In some embodiments, only a portion of the container  120  is frangible, for example, the container  120  can include a frangible portion or cover (e.g., a frangible barrier, film, membrane, or the like). The frangible container  120  can have a first state in which it is intact and the liquid  122  is contained therein, and a second state in which at least a portion of the container  120  is fractured. In the second state of the container  120 , the liquid  122  can be in fluid communication with the reservoir  103  of the biological sterilization indicator  100 , e.g., when the container  120  is positioned in the biological sterilization indicator  100 . 
     As shown in the illustrated embodiment, the container  120  can be held in place within the biological sterilization indicator  100  and/or fractured by an insert  130 , which is described in greater detail below. 
     The first portion  104  of the housing  102  can be adapted to house a majority of the components of the biological sterilization indicator  100 , and can be referred to as a “tube,” “tubular body,” “base,” or the like. The housing  102  can include a reservoir  103  that can be defined by one or both of the first portion  104  and the second portion  106  of the housing  102 . The biological sterilization indicator  100  can further include spores or another source(s) of biological activity  115  (or a locus of spores) positioned in fluid communication with the reservoir  103 . As shown in  FIG. 2 , the second portion  106  of the housing  102  can include one or more apertures  107  to provide fluid communication between the interior of the housing  102  (e.g., the reservoir  103 ) and ambience. For example, the one or more apertures  107  can provide fluid communication between the spores  115  and ambience during a sterilization process, and can serve as an inlet into the biological sterilization indicator  100  and as an inlet of a sterilant path  164  (described in greater detail below). In some embodiments, the second portion  106  of the housing  102  can be coupled to a first (e.g., open) end  101  of the first portion  104  of the housing  102 , and the spores  115  can be positioned at a second (e.g., closed) end  105 , opposite the first end  101 , of the first portion  104  of the housing  102 . 
     In some embodiments, a barrier or filter (e.g., a sterile barrier; not shown) can be positioned in the sterilant path  164  (e.g., at the inlet formed by the aperture  107 ) to inhibit contaminating or foreign organisms, objects or materials from entering the biological sterilization indicator  100 . Such a barrier can include a gas-transmissive, microorganism-impermeable material, and can be coupled to the housing  102  by a variety of coupling means, including, but not limited to, an adhesive, a heat seal, sonic welding, or the like. Alternatively, the barrier can be coupled to the sterilant path  164  via a support structure (such as the second portion  106 ) that is coupled to the first portion  104  of the housing  102  (e.g., in a snap-fit engagement, a screw-fit engagement, a press-fit engagement, or a combination thereof). During exposure to a sterilant, the sterilant can pass through the barrier into the sterilant path  164  and into contact with the spores  115 . 
     In some embodiments, as shown in  FIG. 2 , the housing  102  can include a lower portion  114  and an upper portion  116 , which can be at least partially separated by an inner wall (or partial wall)  118 , ledge, partition, flange, or the like, in which can be formed an opening  117  that provides fluid communication between the lower portion  114  and the upper portion  116 . In some embodiments, the lower portion  114  of the first portion  104  of the housing  102  (sometimes referred to as simply “the lower portion  114 ” or the “the lower portion  114  of the housing  102 ”) can be adapted to house the spores  115  or a locus of spores. In some embodiments, the lower portion  114  can be referred to as the “detection portion” or “detection region” of the housing  102 , because at least a portion of the lower portion  114  can be interrogated for signs of spore growth. In addition, in some embodiments, the upper portion  116  of the first portion  104  of the housing  102  (sometimes referred to as “the upper portion  116 ” or the “the upper portion  116  of the housing  102 ” for simplicity) can be adapted to house at least a portion of the frangible container  120 , particularly before activation. 
     In some embodiments, as shown in  FIGS. 2-4 , the portion of the reservoir  103  that is defined at least partially by the upper portion  116  of the housing  102  can be referred to as a first chamber (or reservoir, zone, region, or volume)  109  and the portion of the reservoir  103  that is defined at least partially by the lower portion  114  of the housing  102  can be referred to as a second chamber (or reservoir, zone, region, or volume)  111 . In some embodiments, the second chamber  111  can be referred to as a “spore growth chamber” or a “detection chamber,” and can include a volume to be interrogated for spore viability to determine the efficacy of a sterilization process. 
     The first chamber  109  and the second chamber  111  can be positioned in fluid communication with each other to allow a sterilant and the liquid  122  to move from (i.e., through) the first chamber  109  to the second chamber  111 . In some embodiments, the degree of fluid connection between the first chamber  109  and the second chamber  111  (e.g., the size of an opening, such as the opening  117 , connecting the first chamber  109  and the second chamber  111 ) can increase after, simultaneously with, and/or in response to the activation step (i.e., the liquid  122  being released from the container  120 ). In some embodiments, the control of fluid communication (or extent of fluid connection) between the first chamber  109  (e.g., in the upper portion  116 ) and the second chamber  111  (e.g., in the lower portion  114 ) can be provided by at least a portion of the insert  130 . 
     The container  120  can be positioned and held in the first chamber  109  during sterilization and when the container  120  is in a first, unfractured, state. The spores  115  can be housed in the second chamber  111  and in fluid communication with ambience when the container  120  is in the first state. The first chamber  109  and the second chamber  111  can be configured such that the container  120  is not present in the second chamber  111 , and particularly, not when the container  120  is in its first, unfractured, state. A sterilant can move into the second chamber  111  (e.g., via the first chamber  109 ) during sterilization, and the liquid  122  can move into the second chamber  111  (e.g., from the first chamber  109 ) during activation, when the container  120  is fractured and the liquid  122  is released into the interior of the housing  102 . 
     As a result, when the container  120  is in the first state, the first chamber  109  and the second chamber  111  can be in fluid communication with one another, and with ambience (e.g., during sterilization). For example, the first chamber  109  and the second chamber  111  can be in fluid communication with ambience via the one or more apertures  107 . In some embodiments, the first chamber  109  and the second chamber  111  can be in fluid communication with ambience in such a way that the first chamber  109  is positioned upstream of the second chamber  111  when a sterilant is entering the biological sterilization indicator  100 . That is, the first chamber  109  can be positioned between the sterilant inlet (e.g., the one or more apertures  107 ) and the second chamber  111 , and the sterilant inlet can be positioned on an opposite side of the first chamber  109  than the second chamber  111 . 
     As shown in  FIGS. 2-4 , in some embodiments, the first chamber  109  can be defined by one or both of the first portion  104  and the second portion  106 , particularly when the container  120  is in the first state. In addition, in some embodiments, the first chamber  109  can include a first end  112  positioned adjacent the open end  101  of the first portion  104  of the housing  102 , adjacent the second portion  106  of the housing  102 , and/or defined at least partially by the second portion  106  of the housing  102 . The first chamber  109  can further include a second end  113  positioned adjacent and in fluid communication with the second chamber  111  and positioned toward the closed end  105  of the housing  102 . The first end  112  of the first chamber  109  can be at defined by the first portion  104  and/or the second portion  106  of the housing  102 . 
     As further shown in  FIGS. 2-4 , in some embodiments, the second chamber  111  can include a first end  124  positioned adjacent and in fluid communication with the first chamber  109  and positioned toward the open end  101  of the housing  102 , and a second end  125  at least partially defined by, including, or positioned adjacent the closed end  105  of the housing  102 . 
     Said another way, as shown in  FIGS. 2-4 , the biological sterilization indicator  100  can include a longitudinal direction D L , and in some embodiments, the first chamber  109  can be positioned longitudinally above the second chamber  111 . 
     In some embodiments, the second chamber  111  can be at least partially defined by, can include, or can be positioned adjacent the closed end  105  of the biological sterilization indicator  100 . In addition, in some embodiments, the second chamber  111  can be smaller (e.g., in volume and/or cross-sectional area) than at least one of the first chamber  109  and the volume of the liquid  122  in the container  120  that will be released when the biological sterilization indicator  100  is activated. As a result, in such embodiments, the second chamber  111  can exhibit an air-lock effect where gas (e.g. air) that is present in the second chamber  111  can inhibit fluid movement into the second chamber  111 . In some embodiments, as described in greater detail below, a fluid path that allows the second chamber  111  to vent to another portion of the biological sterilization indicator  100  can facilitate fluid movement into the second chamber  111 . 
     In some embodiments, the wall  118  (sometimes referred to as a “separating wall”) can be angled or slanted, for example, oriented at a non-zero and non-right angle with respect to a longitudinal direction D L  of the housing  102  (e.g., where the longitudinal direction D L  extends along the length of the housing  102 ). Such angling or slanting of the wall  118  can facilitate the movement of the liquid  122  from the upper portion  116  to the lower portion  114  after sterilization and after the container  120  has been broken to release the liquid  122 . 
     As shown in  FIG. 2 , in some embodiments, the wall  118  can be at least partially formed by a change in the inner dimension of the housing  102 . For example, as shown, the wall  118  can be formed by a decrease in a cross-sectional area from a first longitudinal position in the first chamber  109  to a second longitudinal position in the second chamber  111 . In addition, by way of example only, the internal cross-sectional shape of the housing  102  can change at the transition from the first chamber  109  to the second chamber  111  from being substantially round (e.g., with one flat side that makes up less than 50% of the perimeter) in the first chamber  109  to substantially parallelepipedal (e.g., substantially square) in the second chamber  111 . 
     Furthermore, in some embodiments, the wall  118  can also be at least partially formed by a change in the outer dimension of the housing  102 . As shown in  FIG. 2 , in some embodiments, the housing  102  includes a step (or ledge, overhang, transition, or the like)  123  that is angled consistently with the wall  118  (if the wall  118  is angled), and which includes a change in the outer shape and dimension of the housing  102 . However, it should be understood that in some embodiments, even if the inner dimension of the housing  102  changes to create a second chamber  111  that has a different cross-sectional shape or dimension than the first chamber  109 , the outer shape and dimension of the housing  102  need not change, or change consistently with the change in the inner shape and/or dimension. For example, in some embodiments, the step  123  can be oriented substantially perpendicularly with respect to the longitudinal direction D L . 
     In some embodiments, the reservoir  103  has a volume of at least about 0.5 milliliters (mL), in some embodiments, at least about 1 mL, and in some embodiments, at least about 1.5 mL. In some embodiments, the reservoir  103  has a volume of no greater than about 5 mL, in some embodiments, no greater than about 3 mL, and in some embodiments, no greater than about 2 mL. 
     In some embodiments, the frangible container  120  has a volume of at least about 0.25 mL, in some embodiments, at least about 0.5 mL, and in some embodiments, at least about 1 mL. In some embodiments, the frangible container  120  has a volume of no greater than about 5 mL, in some embodiments, no greater than about 3 mL, and in some embodiments, no greater than about 2 mL. 
     In some embodiments, the volume of the liquid  122  contained in the frangible container  120  is at least about 50 microliters, in some embodiments, at least about 75 microliters, and in some embodiments, at least about 100 microliters. In some embodiments, the volume of the liquid  122  contained in the frangible container  120  is no greater than about 5 mL, in some embodiments, no greater than about 3 mL, and in some embodiments, no greater than about 2 mL. 
     In some embodiments, the first chamber  109  (i.e., formed by the upper portion  116  of the first portion  104  of the housing  102 ) has a volume of at least about 500 microliters (or cubic millimeters), in some embodiments, at least about 1000 microliters, in some embodiments, at least about 2000 microliters, and in some embodiments, at least about 2500 microliters. In some embodiments, the first chamber  109  has a volume of no greater than about 5000 microliters, in some embodiments, no greater than about 4000 microliters, and in some embodiments, no greater than about 3000 microliters. In some embodiments, the first chamber  109  has a volume of about 2790 microliters, or 2800 microliters. 
     In some embodiments, the second chamber  111  (i.e., formed by the lower portion  114  of the first portion  104  of the housing  102 ) has a volume of at least about 5 microliters, in some embodiments, at least about 20 microliters, and in some embodiments, at least about 35 microliters. In some embodiments, the second chamber  111  has a volume of no greater than about 250 microliters, in some embodiments, no greater than about 200 microliters, in some embodiments, no greater than about 175 microliters, and in some embodiments, no greater than about 100 microliters. In some embodiments, the second chamber  111  has a volume of about 208 microliters, or 210 microliters. 
     In some embodiments, the volume of the second chamber  111  is at least about 5% of the volume of the first chamber  109 , and in some embodiments, at least about 7%. In some embodiments, the volume of the second chamber  111  is no greater than about 20% of the volume of the first chamber  109 , in some embodiments, no greater than about 15%, in some embodiments, no greater than about 12%, and in some embodiments, no greater than about 10%. In some embodiments, the volume of the second chamber  111  is about 7.5% of the volume of the first chamber  109 . 
     In some embodiments, the volume of the second chamber  111  is no greater than about 60% of the volume of the liquid  122  housed in the container  120 , in some embodiments, no greater than about 50%, and in some embodiments, no greater than about 25%. In some embodiments, designing the second chamber  111  to have a volume that is substantially less than that of the liquid  122  housed in the container  120  can ensure that the additional liquid volume can compensate for unintended evaporation. 
     In some embodiments, the first chamber  109  (i.e., formed by the upper portion  116  of the first portion  104  of the housing  102 ) has a cross-sectional area (or average cross-sectional area) at the transition between the first chamber  109  and the second chamber  111 , or at the position adjacent the second chamber  111 , of at least about 25 mm 2 ; in some embodiments, at least about 30 mm 2 ; and in some embodiments, at least about 40 mm 2 . In some embodiments, the first chamber  109  has a cross-sectional area at the transition between the first chamber  109  and the second chamber  111 , or at the position adjacent the second chamber  111 , of no greater than about 100 mm 2 , in some embodiments, no greater than about 75 mm 2 , and in some embodiments, no greater than about 50 mm 2 . 
     In some embodiments, the second chamber  111  (i.e., formed by the lower portion  114  of the first portion  104  of the housing  102 ) has a cross-sectional area at the transition between the first chamber  109  and the second chamber  111 , or at the position adjacent the first chamber  109 , of at least about 5 mm 2 , in some embodiments, at least about 10 mm 2 , and in some embodiments, at least about 15 mm 2 . In some embodiments, the second chamber  111  has a cross-sectional area (or average cross-sectional area) of no greater than about 30 mm 2 , in some embodiments, no greater than about 25 mm 2 , and in some embodiments, no greater than about mm 2    
     In some embodiments, the cross-sectional area of the second chamber  111  at the transition between the first chamber  109  and the second chamber  111  can be no greater than about 60% of the cross-sectional area of the first chamber  109  at the transition, in some embodiments, no greater than about 50%, in some embodiments, no greater than about 40%, and in some embodiments, no greater than about 30%. 
     In some embodiments, the biological sterilization indicator  100  can further include a substrate  119 . In some embodiments, as shown in  FIGS. 2-4 , the substrate  119  can be dimensioned to be positioned adjacent the wall  118 , and particularly, to rest atop the wall  118 . The substrate  119  can be positioned between the upper portion  116  and the lower portion  114  of the biological sterilization indicator  100  and, in some embodiments, can at least partially define the first chamber  109  and the second chamber  111 . As such, in some embodiments, the substrate  119  can be positioned between the container  120  and the spores  115 . In some embodiments, the substrate  119  can be positioned in the first chamber  109 , or on a first chamber side of the wall  118 , such that the substrate  119  is not positioned in the second chamber  111 . 
     In addition, the substrate  119  can be positioned to minimize diffusion of an assay signal (e.g., fluorescence) out of the second chamber  111 . In some embodiments, depending on the material makeup of the substrate  119 , the substrate  119  can also absorb dyes, indicator reagents, or other materials from solution that may inhibit accurate reading of a signal from the biological sterilization indicator  100  (i.e., “inhibitors”). In some embodiments, as shown in  FIG. 2 , the substrate  119  can include one or more apertures  121 , which can be configured to control (i.e., facilitate and/or limit, depending on number, size, shape, and/or location) fluid movement between the first chamber  109  and the second chamber  111  of the biological sterilization indicator  100 , and particularly, which can facilitate movement of the liquid  122  to the spores  115  when the container  120  is fractured. By way of example only, particular benefits or advantages were observed when the aperture  121  was positioned front of (or “forward of”) the center of the substrate  119 , as shown. In the embodiment illustrated in  FIGS. 1-4 , the “front” of the biological sterilization indicator  100  or components therein can generally be described as being toward a flat face  126 . In general, the “front” of the biological sterilization indicator  100  can refer to the portion of the biological sterilization indicator  100  that will be interrogated by the reading apparatus  12 . 
     In addition, by way of example only, the aperture  121  is illustrated as being circular or round; however, other cross-sectional aperture shapes are possible and within the scope of the present disclosure. Furthermore, by way of example only, and as shown in  FIG. 2 , the substrate  119  is shaped to substantially fill the first chamber cross-sectional area at the transition between the first chamber  109  and the second chamber  111 . However, other shapes of the substrate  119  are possible and can be adapted to accommodate the housing  102 , the first chamber  109 , the second chamber  111 , the wall  118 , or another component of the biological sterilization indicator  100 . 
     In some embodiments, the substrate  119  can be formed of a variety of materials to accomplish one or more of the above functions. Examples of substrate materials can include, but are not limited to, cotton, glass wool, cloth, nonwoven polypropylene, nonwoven rayon, nonwoven polypropylene/rayon blend, nonwoven nylon, nonwoven glass fiber or other nonwoven fibers, filter papers, microporous hydrophobic and hydrophilic films, glass fibers, open celled polymeric foams, and semi-permeable plastic films (e.g., particle filled films, thermally induced phase separation (TIPS) membranes, etc.), and combinations thereof. For example, in embodiments in which the substrate  119  can be used to selectively concentrate one more indicator reagents (e.g., bromocresol purple (BCP)), the substrate  119  can be formed of a charged nylon (such as a reprobing, charged transfer membrane available from GE Water &amp; Process Technologies, Trevose, Pa., under the trade designation “MAGNAPROBE” (e.g., 0.45 micron pore size, 30 cm×3 m roll, Catalog No. NP0HY00010, Material No. 1226566)). 
     The substrate  119  is described in greater detail in co-pending U.S. Patent Application Nos. 61/408,988 and 61/408,977, each of which is incorporated herein by reference in its entirety. Examples of methods and systems that can employ the substrate  119  are also described in co-pending U.S. Patent Application No. 61/408,887, entitled “Method of Detecting a Biological Activity,” and U.S. Patent Application No. 61/408,966, entitled “Method of Detecting a Biological Activity,” each of which is incorporated herein by reference in its entirety. 
     In some embodiments, at least a portion of one or more of the insert  130 , the wall  118 , and/or the substrate  119 , or an opening therein, can provide fluid communication between the first chamber  109  (e.g., in the upper portion  116 ) and the second chamber  111  (e.g., in the lower portion  114 ), and/or can control the fluid communication between the first chamber  109  and the second chamber  111  (e.g., by controlling the extent of fluid connection between the first chamber  109  and the second chamber  111 ). 
     The biological sterilization indicator  100  can include a first fluid path  160  that can be positioned to fluidly couple the first chamber  109  and the second chamber  111 , and which can allow sterilant (e.g., during sterilization, when the container  120  is in a first, unfractured state) and/or the liquid  122  (e.g., after sterilization and during activation, when the container  120  is in a second, fractured, state) to reach the spores  115 . In the illustrated embodiment the first fluid path  160  can generally be defined by one or more of the following: (1) the insert  130 , e.g., via an aperture  177  described below, an opening formed in the insert  130 , and/or any open spaces around the insert  130 , such as between the insert  130  (e.g., a front portion thereof) and the housing  102 ; (2) the wall  118 , e.g., the aperture  117  defined by the wall  118 ; (3) the substrate  119 , e.g., the aperture  121  formed therein, or any open spaces around the substrate  119 , such as between the substrate  119  (e.g., a front portion thereof) and the housing  102 ; (4) the housing  102 , e.g., any openings or spaces formed therein; and combinations thereof. As a result, the first fluid path  160  is generally represented by an arrow, as shown in  FIG. 3 . 
     The biological sterilization indicator  100  can further include a second fluid path  162  positioned to fluidly couple the second chamber  111  with another chamber or portion of the biological sterilization indicator  100 , such as the first chamber  109 . The second fluid path  162  can be further positioned to allow gas that was previously present in the second chamber  111  to be displaced and to exit the second chamber  111 , for example, when the sterilant and/or the liquid  122  is moved into the second chamber  111 . As such, the second fluid path  162 , which is described in greater detail below, can serve as an internal vent in the biological sterilization indicator  100 . 
     In some embodiments, the substrate  119  can provide a physical barrier or blockage between the first chamber  109  and the second chamber  111  which can allow for at least one of the following: controlling the sterilant delivery rate/kill rate at which sterilant is delivered into the second chamber  111 ; controlling the diffusion of spores  115  and/or detectable products out of the second chamber  111 ; controlling the delivery rate of the liquid  122  to the second chamber  111  (and to the spores  115 ) when the container  120  is in the second, fractured, state; or a combination thereof. 
     Because, in some embodiments, the substrate  119  can provide a physical barrier to delivering the liquid  122  to the second chamber  111  during activation (i.e., when the container  120  is in the second state), aperture  121  in the substrate  119  and/or the angle of the substrate  119  can be controlled to effect a desired liquid delivery rate. In addition, or alternatively, the second fluid path  162  can provide a vent for any gas (e.g., air) that is trapped in the second chamber  111  to facilitate moving the liquid  122  through or past the substrate  119  and into the second chamber  111  when desired. 
     In addition, or alternatively, the housing  102  can be configured (e.g., formed of an appropriate material and/or configured with microstructured grooves or other physical surface modifications) to facilitate moving the liquid  122  to the second chamber  111  when desired. 
     In some embodiments, the liquid  122  can include a nutrient medium for the spores, such as a germination medium that will promote germination of surviving spores. In some embodiments, the liquid  122  can include water (or another solvent) that can be combined with nutrients to form a nutrient medium. Suitable nutrients can include nutrients necessary to promote germination and/or growth of surviving spores and may be provided in a dry form (e.g., powdered form, tablet form, caplet form, capsule form, a film or coating, entrapped in a bead or other carrier, another suitable shape or configuration, or a combination thereof) in the reservoir  103 , for example, in a region of the biological sterilization indicator  100  near the spores  115 . 
     The nutrient medium can generally be selected to induce germination and initial outgrowth of the spores, if viable. The nutrient medium can include one or more sugars, including, but not limited to, glucose, fructose, cellibiose, or the like, or a combination thereof. The nutrient medium can also include a salt, including, but not limited to, potassium chloride, calcium chloride, or the like, or a combination thereof. In some embodiments, the nutrient can further include at least one amino acid, including, but not limited to, at least one of methionine, phenylalanine, and tryptophan. 
     In some embodiments, the nutrient medium can include indicator molecules or reagents, for example, indicator molecules having optical properties that change in response to germination or growth of the spores. Suitable indicator molecules or reagents can include, but are not limited to, pH indicator molecules (e.g., bromocresol purple (BCP), bromocresol green (BCG), chlorophenol red (CPR), bromthymol blue (BTB), bromophenol blue (BPB), other sulfonephthalein dyes, methyl red, or combinations thereof), enzyme substrates (e.g., 4-methylumbelliferyl-α-D-glucoside), DNA binding dyes, RNA binding dyes, other suitable indicator molecules, or a combination thereof. In some embodiments, the combination of bromcresol purple and 4-methylumbelliferyl-α-D-glucoside represents an example of a pair of indicator reagents that can be employed together. This combination can be used to detect a first biological activity such as the fermentation of a carbohydrate to acid end products and a second biological activity such as α-D-glucosidase enzyme activity, for example. These activities can indicate the presence or absence of a viable spore following the exposure of a biological sterilization indicator to a sterilization process, for example. The bromcresol purple can be used at a concentration of about 0.03 g/L, for example, in an aqueous mixture. The 4-methylumbelliferyl-α-D-glucoside can be used, for example, at a concentration of about 0.05 to about 0.5 g/L (e.g., about 0.05 g/L, about 0.06 g/L, about 0.07 g/L, about 0.08 g/L, about 0.09 g/L, about 0.1 g/L, about 0.15 g/L, about 0.2 g/L, about 0.25 g/L, about 0.3 g/L, about 0.35 g/L, about 0.4 g/L, about 0.45 g/L, about 0.5 g/L), for example, in an aqueous mixture. 
     As shown in  FIGS. 2-4 , the biological sterilization indicator  100  can further include an insert  130 . In some embodiments, the insert  130  can be adapted to hold or carry the container  120 , such that the container  120  is held intact in a location separate from the spores  115  during sterilization. That is, in some embodiments, the insert  130  can include (or function as) a carrier  132  for the container  120 , particularly, before the container  120  is broken during the activation step (i.e., the step in which the liquid  122  is released from the container  120  and introduced to the spores  115 , which can occur after a sterilization process). In some embodiments, the insert  130  can be further adapted to allow the container  120  to move at least somewhat in the housing  102 , e.g., longitudinally with respect to the housing  102 . The insert  130  of the embodiment illustrated in  FIGS. 1-4  is described in greater detail below. Examples of other suitable inserts and carriers are described in co-pending U.S. Patent Application Nos. 61/226,937 (Docket No. 65578US002). 
     In some embodiments, the biological sterilization indicator  100  can further include a spore carrier  135 , as shown in  FIGS. 2-4 . However, in some embodiments, the insert  130  can be modified to include a portion adapted to house the spores  115 . For example, in some embodiments, the insert  130  and the spore carrier  135  can be integrally formed as one insert comprising a first portion adapted to hold and eventually fracture the container  120 , when desired, and a second portion adapted to house the spores  115  in a region of the biological sterilization indicator  100  that is separate from the container  120  during sterilization (i.e., prior to fracture). 
     As shown in  FIGS. 2-4 , the spore carrier  135  can include a spore reservoir  136  (which can also be referred to as a depression, divot, well, recess, or the like), in which the spores  115  can be positioned, either directly or on a substrate. In embodiments employing a nutrient medium that is positioned to be mixed with the liquid  122  when it is released from the container  120 , the nutrient medium can be positioned near or in the spore reservoir  136 , and the nutrient medium can be mixed with (e.g., dissolved in) the water when the water is released from the container  120 . By way of example only, in embodiments in which the nutrient medium is provided in a dry form, the dry form can be present within the reservoir  103 , the spore reservoir  136 , on a substrate for the spores, or a combination thereof. In some embodiments, a combination of liquid and dry nutrient media can be employed. 
     In some embodiments, the spore reservoir  136  has a volume of at least about 1 microliter, in some embodiments, at least about 5 microliters, and in some embodiments, at least about 10 microliters. In some embodiments, the spore reservoir  136  has a volume of no greater than about 250 microliters, in some embodiments, no greater than about 175 microliters, and in some embodiments, no greater than about 100 microliters. 
     As shown in  FIGS. 3 and 4 , in some embodiments, the biological sterilization indicator  100  can further include a rib or protrusion  165  that can be coupled to or integrally formed with a wall  108  of the housing  102 , which can be positioned to maintain the spore carrier  135  in a desired location in the housing  102  and/or at a desired angle or orientation, for example, with respect to detection systems (e.g., optical detection systems) of the reading apparatus  12 . 
     As shown in  FIGS. 2-4 , the second portion  106  of the housing  102  can be adapted to be coupled to the first portion  104 . For example, as illustrated in  FIGS. 1-4 , the second portion  106  can be adapted to be coupled to the upper portion  116  (e.g., the first end  101 ) of the first portion  104  of the housing  102 . In some embodiments, as shown in  FIGS. 1-4 , the second portion  106  can be in the form of a cap that can be dimensioned to receive at least a portion of the first portion  104  of the housing  102 . 
     As shown in  FIG. 3 , before activation, the second portion  106  can be in a first “unactivated” position  148  with respect to the first portion  104 , and the container  120  can be in a first, intact, state. As shown in  FIG. 4 , the second portion  106  of the housing  102  can be moved to a second “activated” position  150  (e.g., where the second portion  106  is fully depressed) with respect to the first portion  104 , and the container  120  can be in a second, fractured, state. For example, after sterilization, the biological sterilization indicator  100  can be activated by moving the second portion  106  from the first position  148  to the second position  150  (i.e., a sufficient amount) to cause fracturing of the container  120  and to release the liquid  122  from the container  120 , to allow the liquid  122  to be in fluid communication with the spores  115 . The biological sterilization indicator  100  can be activated prior to positioning the biological sterilization indicator  100  in the well  14  of the reading apparatus  12 , after positioning the biological sterilization indicator  100  in the well  14 , or as the biological sterilization indicator  100  is positioned in the well  14  (i.e., the biological sterilization indicator  100  can be slid into place in the well  14 , and the second portion  106  can continue to be pressed until it is in its second position  150 , e.g., in which the bottom of the well  14  provides sufficient resistance to move the second portion  106  to its second position  150 ). The second position  150  can be located closer to the closed end  105  of the first portion  104  of the biological sterilization indicator  100  than the first position  148 . 
     A variety of coupling means can be employed between the first portion  104  and the second portion  106  of the housing  102  to allow the first portion  104  and the second portion  106  to be removably coupled to one another, including, but not limited to, gravity (e.g., one component can be set atop another component, or a mating portion thereof), screw threads, press-fit engagement (also sometimes referred to as “friction-fit engagement” or “interference-fit engagement”), snap-fit engagement, magnets, adhesives, heat sealing, other suitable removable coupling means, and combinations thereof. In some embodiments, the biological sterilization indicator  100  need not be reopened and the first portion  104  and the second portion  106  need not be removably coupled to one another, but rather can be permanently or semi-permanently coupled to one another. Such permanent or semi-permanent coupling means can include, but are not limited to, adhesives, stitches, staples, screws, nails, rivets, brads, crimps, welding (e.g., sonic (e.g., ultrasonic) welding), any thermal bonding technique (e.g., heat and/or pressure applied to one or both of the components to be coupled), snap-fit engagement, press-fit engagement, heat sealing, other suitable permanent or semi-permanent coupling means, and combinations thereof. One of ordinary skill in the art will recognize that some of the permanent or semi-permanent coupling means can also be adapted to be removable, and vice versa, and are categorized in this way by way of example only. 
     As shown in  FIGS. 3-4 , the second portion  106  can be movable between a first longitudinal position  148  with respect to the first portion  104  and a second longitudinal position  150  with respect to the first portion  104 ; however, it should be understood that the biological sterilization indicator  100  could instead be configured differently, such that the first and second positions  148  and  150  are not necessarily longitudinal positions with respect to one or both of the first portion  104  and the second portion  106  of the housing  102 . 
     The second portion  106  can further include a seal  156  (e.g., a projection, a protrusion, a flap, flange, o-ring, or the like, or combinations thereof) that can be positioned to contact the first end  101  of the first portion  104 , and particularly, an open upper end  157  of the first portion  104  to close or seal (e.g., hermetically seal) the biological sterilization indicator  100  after the second portion  106  has been moved to the second position  150  and the liquid  122  has been released from the container  120 . The seal  156  can take a variety of forms and is shown in  FIGS. 3 and 4  by way of example as forming an inner ring or cavity that together with the wall  110  of the second portion  106  is dimensioned to receive the upper end  157  of the first portion  104  of the housing  102  to seal the biological sterilization indicator  100 . 
     In some embodiments, one or both of the seal  156  and the upper end  157  can further include a structure (e.g., a protrusion) configured to engage the other of the upper end  157  and the seal  156 , respectively, in order to couple the second portion  106  of the housing  102  to the first portion  104  of the housing  102 . 
     In addition, in some embodiments, the second portion  106  of the housing  102  can be coupled to the first portion  104  of the housing  102  to seal the biological sterilization indicator  100  from ambience after activation. Such sealing can inhibit contamination, evaporation, or spilling of the liquid  122  after it has been released from the container  120 , and/or can inhibit contamination of the interior of the biological sterilization indicator  100 . 
     The seal  156  can be configured to have a length in the longitudinal direction D L  of the biological sterilization indicator  100  to accommodate different degrees or levels of closure. That is, in some embodiments, the “second position”  150  of the second portion  106  of the housing  102  can be any position in which at least a portion of the seal  156  has engaged a portion (e.g., the upper end  157 ) of the first portion  104  of the housing  102  such that the interior of the biological sterilization indicator  100  is sealed from ambience. The biological sterilization indicator  100  and the biological sterilization indicator system  10  can correspondingly be configured such that if the reading apparatus  12  detects that the second portion  106  has moved to the second position  150 , the user knows that the seal  156  is engaged. 
     The insert  130  will now be described in greater detail, with particular reference to  FIGS. 2-4 . 
     As shown in  FIG. 3 , before activation, the second portion  106  can be in a first position  148  with respect to the first portion  104 . In the first position  148 , the container  120  can be held intact in a position separate from the lower portion  114  or the spores  115 , and the liquid  122  can be contained within the container  120 . 
     As shown in  FIG. 4 , after sterilization, the biological sterilization indicator  100  can be activated to release the liquid  122  from the container  120  to move the liquid  122  to the spores  115 . That is, the second portion  106  of the housing  102  can be moved to a second position  150  with respect to the first portion  104 . When the second portion  106  is moved from the first position  148  to the second position  150 , the seal  156  of the second portion  106  of the housing  102  can engage the upper end  157  of the first portion  104  to seal the reservoir  103  of the biological sterilization indicator  100  from ambience. In such embodiments, the second portion  106  can reversibly engage the first portion  104  in the second position  150 , and in some embodiments, the second portion  106  can irreversibly engage the first portion  104 . However, it should be understood that the structures and coupling means for the first portion  104  and the second portion  106  are shown in  FIGS. 3 and 4  by way of example only, and any of the above-described coupling means can instead be employed between the first portion  104  and the second portion  106  of the housing  102 . 
     The insert  130  can be adapted to hold or carry the container  120 , such that the container  120  is held intact in a location separate from the spores  115  during sterilization. That is, as mentioned above, in some embodiments, the insert  130  can include (or function as) a carrier  132  for the container  120 , particularly, before the container  120  is broken during the activation step (i.e., the step in which the liquid  122  is released from the container  120  and introduced to the spores  115 , which typically occurs after a sterilization process). 
     In addition, the insert  130  can be adapted to hold the container  120  intact in a position in the housing  102  that maintains at least a minimal spacing (e.g., a minimal cross-sectional area of space) between the container  120  and the housing  102  and/or between the container  120  and any other components or structures in the housing  102  (e.g., at least a portion of the insert  130 , such as the carrier  132 , etc.), for example, to maintain a substantially constant sterilant path  164  in the biological sterilization indicator  100 . In some embodiments, the insert  130  can be adapted to hold the container  120  in a substantially consistent location in the housing  102 . 
     In some embodiments, as shown in  FIG. 2 , at least a portion of the housing  102  can include a tapered portion  146  in which the housing  102  (e.g., the wall  108  and/or an inner surface thereof) generally tapers in the longitudinal direction D L  of the housing  102 . As a result, the cross-sectional area in the housing  102  can generally decrease along the longitudinal direction D L . 
     In some cases, without providing the means to maintain at least a minimal spacing around the container  120  (e.g., between the container  120  and surrounding structure), there can be a possibility that the container  120  can become positioned in the housing  102  (e.g., in the tapered portion  146 ) in such a way that it obstructs or blocks the sterilant path  164 . However, the biological sterilization indicator  100  of the present disclosure is designed to inhibit this from occurring. For example, in the embodiment illustrated in  FIGS. 1-4 , the insert  130  (and particularly, the carrier  132 ) can be configured to hold the container  120  out of the tapered portion  146  of the housing  102 , such that at least a minimal cross-sectional area is maintained around the container  120  in any orientation of the biological sterilization indicator  100  prior to activation. For example, in the embodiment illustrated in  FIGS. 1-4 , even if the biological sterilization indicator  100  is tipped upside down, the container  120  may fall away from contact with the insert  130 , but in no orientation, is the container  120  moved any closer to the tapered portion  146 , or the spores  115  until activation of the biological sterilization indicator  100 . In addition, until activation, at least a minimal spacing (and particularly, a cross-sectional area of that spacing) between the container  120  and the housing  102  and/or the insert  130  can be maintained to provide a substantially constant sterilant path  164 , for example, around the container  120 . 
     In some embodiments, the relative sizing and positioning of the components of the biological sterilization indicator  100  can be configured such that, before activation, the container  120  is held intact in a substantially consistent location in the biological sterilization indicator  100 . Such a configuration can provide a substantially constant sterilant path  164  and can maintain the container  120  in a position such that the container  120  is not able to move substantially, if at all, in the biological sterilization indicator  100  before activation. 
     In some embodiments, at least a portion of the insert  130  can be adapted to allow the container  120  to move in the housing  102 , e.g., longitudinally with respect to the housing  102 , between a first (longitudinal) position in which the container  120  is intact and a second (longitudinal) position in which at least a portion of the container  120  is fractured. By way of example only, the insert  130  can include one or more projections or arms  158  (two projections  158  spaced about the container  120  are shown by way of example only) adapted to hold and support the container  120  before activation and to allow the container  120  to move in the housing  102  during activation, for example, when the second portion  106  is moved with respect to the first portion  104  of the housing  102 . The projections  158  can also be adapted (e.g., shaped and/or positioned) to fracture the container  120  in a desired manner when the biological sterilization indicator is activated. As a result, the insert  130  can sometimes function to hold the container  120  intact before activation, and can function to break the container  120  during activation. As a result, the insert  130 , or a portion thereof, can sometimes be referred to as a “carrier” (e.g., the carrier  132 ) and/or a “breaker.” 
     By way of example only, the projections  158  are shown in  FIGS. 2-4  as being coupled to a base or support  127  adapted to abut the separating wall  118 . For example, the base  127  can be dimensioned to be received in the reservoir  103  and dimensioned to sit atop, abut, or otherwise cooperate with or be coupled to the separating wall  118 . Such coupling with an internal structure of the biological sterilization indicator  100  can provide the necessary resistance and force to break the container  120  when desired. In some embodiments, however, the insert  130  does not include the base  127 , and the projections  158  can be coupled to or form a portion of the housing  102 . In some embodiments, the insert  130  is integrally formed with or provided by the housing  102 . 
     As shown in  FIGS. 2-4 , the insert  130  can further include a sidewall  131  that connects the projections  158  and is shaped to accommodate an inner surface of the housing  102  and/or an outer surface of the container  120 . Such a sidewall  131  can provide support and rigidity to the projections  158  to aid in reliably breaking the container  120  in a consistent manner. The sidewall  131  can also be shaped and dimensioned to guide the container  120  in a desired manner as it is moved in the housing  102  during activation, for example, to contact the projections  158  in a desired way to reliably fracture the container  120 . 
     The sidewall  131  and/or the wall  108  of the housing  102  (or an inner surface thereof) can also be shaped to define at least a portion of the second fluid path  162  of the biological sterilization indicator  100 , for example, between an outer surface of the insert  130  and an inner surface of the housing  102 . In some embodiments, a channel can be formed in one or both of the insert  130  and the housing  102  (e.g., in the wall  108  of the housing  102 ) that together define the second fluid path  162 . 
     The second fluid path  162  can provide an internal vent within the biological sterilization indicator  100  to allow trapped air to escape the second chamber  111  of the biological sterilization indicator  100  as the liquid  122  is released from the container  120  (1) during activation, to facilitate moving the liquid  122  into the spore chamber  111  of the biological sterilization indicator  100 ; and/or (2) during sterilization, to facilitate moving a sterilant into the spore chamber  111  (i.e., into contact with the spores  115 ). The second fluid path  162  is described in greater detail in co-pending U.S. Patent Application No. 61/408,988. 
     By way of example only, the projections  158  are illustrated as being relatively rigid and stationary. That is, in some embodiments, the projections  158  may not be adapted to substantially flex, distort, deform or otherwise heed to the container  120  as it is moved in the housing  102 . Rather, in some embodiments, as shown in  FIGS. 2-4 , the projections  158  can each be configured to have an upper end  159  atop which the container  120  can be positioned and held intact before activation. As shown in  FIG. 3 , in some embodiments, the projections  158  can be positioned to fracture the container  120  at its radiused end, for example, when an oblong or capsule-shaped container  120  is employed. 
     One potential advantage of having the projections  158  form at least a portion of the carrier  132  is that the bottom of the container  120  can be unrestricted when the container  120  is fractured, such that the liquid  122  can be released from the container  120  and moved toward the spores  115  with relative ease and reliability. 
     In such embodiments, the insert  130  can be used to fracture the container  120  in a direction that is substantially perpendicular to a flat side of the container  120 , for example, when an oblong or capsule-shaped container  120  is employed. In such embodiments, fracturing the container  120  along its side can be achieved, along with maintaining some open spaces around the lower end of the container  120  to facilitate moving the liquid  122  from the container  120  to the proximity of the spores  115  when the container  120  is fractured. 
     As mentioned above, the projections  158  can be adapted to fracture the container  120  as the container  120  is moved with respect to the housing  102  (e.g., along the longitudinal direction D L ), for example, in response to the second portion  106  of the housing  102  being moved with respect to the first portion  104  of the housing  102  (e.g., from the first position  148  to the second position  150 ). 
     In some embodiments, the projections  158  can include one or more edges (e.g., tapered edges) or points or otherwise be configured to concentrate the crushing force to increase the pressure on the container  120  in the regions adjacent the projections  158 , and to facilitate fracturing the container  120  more easily and in one or more desired regions. In some embodiments, such concentration of force can reduce the total effort or force needed to move the second portion  106  with respect to the first portion  104  and to fracture the container  120  (or a portion thereof). 
     As shown in  FIGS. 2-4 , the projections  158  are integrally formed with the base  127  of the insert  130 ; however, it should be understood that the projections  158  can instead be integrally formed with the wall  108  of the housing  102 . In addition, in some embodiments, the projections  158  can be coupled to the housing  102 , or the projections  158  and the base  127  can be provided by separate inserts. In such embodiments, the projections  158  can each be a separate insert, or multiple projections  158  can be provided by one or more inserts. In addition, the insert  130  can be configured to abut the wall  118  to inhibit movement of the first portion the insert  130  into the proximity of the spores  115  (e.g., the lower portion  114  of the housing  102 ). 
     In addition, in some embodiments, as shown in  FIGS. 2-4 , the projections  158  can extend a distance along the longitudinal direction D L , and the length and/or thickness (e.g., which can vary along the length) of the projections  158  can be tailored to control the fracturing of the container  120  at a desired position in the housing  102  and in a desired manner. The configuration of the projections  158  is shown in  FIGS. 2-4  by way of example only. 
     In general, each of the projections  158  is shown by way of example only as increasing in thickness (e.g., inwardly toward the container  120  or center of the housing  102 ) along the longitudinal direction D L  toward the spores  115 . Such a configuration can decrease the cross-sectional area that is available to the container  120 , as the container  120  is moved toward the spores  115 , for example, in response to the second portion  106  being moved to the second position  150 . 
     Furthermore, the biological sterilization indicator  100  is shown in  FIGS. 2-4  as including two projections  158  and a sidewall  131  by way of example only, but it should understood that one projection  158  or as many as structurally possible, and other configurations, can be employed. In addition, the projections  158  can be shaped and dimensioned as desired, depending on the shape and dimensions of the housing  102 , on the shape and dimensions of the container  120 , on the shape and dimensions of the insert  130 , and/or on the manner and position desired for fracturing the container  120 . 
     As mentioned above, in some embodiments, at least a portion of the housing  102  can be tapered (see, e.g., the tapered portion  146  in  FIG. 2 ). As a result, the cross-sectional area in the housing  102  can generally decrease along the longitudinal direction D L . However, it should be understood that the inner dimensions of the housing  102  can generally decrease in the tapered portion along the longitudinal direction D L  without the outer dimensions of the housing  102  changing. In some embodiments, the outer dimensions of the housing  102  can be uniform along its length, even though the inner portion of the housing  102  tapers along its length. In some embodiments, the one or more projections  158  alone can vary in thickness (i.e., toward the container  120 , e.g., in a radial direction) along the longitudinal direction D L , such that the cross-sectional area available to the container  120  generally decreases as the container  120  is moved in the housing  102  during activation, even though the dimensions of the housing  102  do not change (e.g., even if the housing  102  does not include any tapered portion  146 , either internally or externally). 
     As shown in  FIGS. 2-4 , the upper end  159  of each of the projections  158  includes a rounded, curved or arcuate surface, which can facilitate movement of the container  120  from the first position  148  in which the container  120  sits at least partially above the upper end  159  of the projection  158  to a position in which the container  120  is forced, at least partially, into the smaller cross-sectional area region in between the projections  158  (or between the wall  108  of the housing  102  and one or more projections  158 ). In addition, the rounded upper end  159  can inhibit premature breakage of the container  120 , which can inhibit premature activation of the biological sterilization indicator  100  (i.e., premature release of the liquid  122 ). 
     In some embodiments, as shown in  FIG. 3 , the insert  130  can be sized and shaped to allow the container  120  to be held above the projections  158  and out from the region adjacent any portion of an inwardly-facing surface of one or more of the projections  158  to inhibit accidental or premature activation of the biological sterilization indicator  100 . Such a configuration can also inhibit inadvertent breakage due to shock or material expansion (e.g., due to exposure to heat during a sterilization process). 
     As shown in  FIGS. 2-4 , the carrier  132 , which can be formed at least partially by the upper ends  159  of the projections  158 , can be configured to hold a bottom portion of the container  120 , and the projections  158  can be positioned to fracture the container  120  at a location near the bottom of the container  120  as it is positioned in the housing  102 . Such a configuration can allow the container  120  to be broken near its bottom and can facilitate removal of the liquid  122  from the container  120 , which can enhance the availability of the liquid  122  to the spores  115 , and can enhance the reliability of releasing the liquid  122  into fluid communication with the spores  115  (e.g., with the spore reservoir  136 ). Such a configuration is shown by way of example only, however, and it should be understood that the projections  158  can be configured and positioned to fracture the container  120  in any desired manner. 
     Some embodiments of the present disclosure provide optimal and safe breakage of a frangible container  120  with relatively low force, while enhancing transfer of liquid  122  to the spore region (e.g., the second chamber  111  of the housing  102 ) of the biological sterilization indicator  100 , and/or enhancing containment of the liquid  122  in the spore region of the biological sterilization indicator  100 . In addition, some embodiments of the present disclosure operate to drive a liquid to a particular area of the biological sterilization indicator  100 , such as a spore detection area (e.g., the second chamber  111 ) of the biological sterilization indicator  100 . 
     In the embodiment illustrated in  FIGS. 1-4 , the insert  130  is illustrated as including two projections  158  that are approximately equally spaced about the container  120  and/or about the sidewall  131 . However, in some embodiments, the sidewall  131  can include one solid (e.g., substantially annular or semi-annular) projection  158  that extends radially inwardly from the sidewall  131 . Furthermore, in some embodiments, the sidewall  131  can extend further around the inner surface of the housing  102  than what is illustrated. However, employing one or more narrower (e.g., in an angular dimension) projections  158 , such as those shown in  FIGS. 2-4 , can provide a substantially constant or substantially unobstructed sterilant path  164  around the container  120 . 
     Whether the insert  130  includes one or more projections  158  or sidewalls  131 , the insert  130  can be configured to hold the container  120  in the housing  102  in a consistent location to provide a substantially constant sterilant path  164  during sterilization. For example, rather than allowing the container  120  to move or roll around (e.g., radially and/or longitudinally) in the housing  102  before activation (e.g., during sterilization), the insert  130  can hold the container  120  in a substantially consistent position, which can allow a sterilant a substantially consistent and relatively unobstructed path between an outer surface of the container  120  and an inner surface of the housing  102 , with little or no opportunity for inadvertent blockage. 
     As shown in  FIGS. 2-4 , the insert  130  can further include one or more projections  161  positioned substantially horizontally or perpendicularly with respect to the longitudinal direction D L  of a biological sterilization indicator (e.g., when the insert  130  is positioned in a biological sterilization indicator). The projections  161  can be referred to as “second projections” or “horizontal projections,” while the projections  158  used to hold and/or break the container  120  can be referred to as “first projections” or “vertical projections.” The second projections  161  are not angled downwardly like the base  127 . As a result, the second projections  161  can be used for a variety of purposes. For example, the second projections  161  can stabilize the insert  130  (e.g., aid in holding the insert  130  in a desired position in the housing  102  of the biological sterilization indicator  100 ) under the force of fracturing the container  120 . In addition, the second projections  161  can function to retain and/or collect fractured portions of the container  120  after it has been fractured to inhibit movement of such portions into the proximity of spores in the biological sterilization indicator, which could negatively affect spore growth and/or detection of spore growth. Other shapes and configurations of the second projections  161  can be employed that still allow for fluid movement down to the spores  115  while inhibiting solid movement down to the spores  115 . 
     In some embodiments, the insert  130  (e.g., the base  127 ) can be adapted for one or more of facilitating or allowing fluid movement (e.g., movement of the liquid  122 ) into the second chamber  111  (i.e., the lower portion  114 ) of the housing  102 ; minimizing movement of fractions or portions (e.g., solids) of the fractured container  120  into the second chamber  111  of the housing  102 , that is, collecting and/or retaining portions of the fractured container  120 ; and/or minimizing diffusion of the spores  115  and/or signals out of the second chamber  111  of the housing  102 . For example, in some embodiments, the base  127  can be configured to function as a grate or filter. In some embodiments, spore growth is determined by fluorescent indicators/molecules (e.g., fluorophores) or other markers. In some embodiments, if the liquid level after activation in the biological sterilization indicator  100  is above the location of the spores  115 , such molecules or markers, or the spores  115  themselves, can move or diffuse away from or out of the spore reservoir  136  and, potentially, out of the second chamber  111  of the housing  102 . As a result, portions of the biological sterilization indicator  100  (e.g., the insert  130 ) can be configured to inhibit undesirable diffusion of various indicators, molecules, and/or markers out of the second chamber  111  of the biological sterilization indicator  100 . In some embodiments, as described above, the substrate  119  can also inhibit such undesirable diffusion. 
     In the embodiment illustrated in  FIGS. 1-4 , the base  127  of the insert  130  is generally U-shaped or horseshoe-shaped and includes a central aperture  177  (see  FIG. 2 ) that facilitates the movement of sterilant toward the spores  115  during sterilization and the movement of the liquid  122  toward the spores  115  during activation. The horseshoe shape of the base  127  can increase the opening between the upper portion  116  (i.e., the first chamber  109 ) and the lower portion  114  (i.e., the second chamber  111 ) of the housing  102 ; however, this shape is shown by way of example only, and other shapes can be employed. 
     In some embodiments, the insert  130  can be described as including one or more downwardly-extending projections  127  adapted to abut or otherwise couple to the wall  118  or another internal structure of the biological sterilization indicator  100  to provide a base or support for the insert  130 , to inhibit movement of the insert  130  and container  120  relative to the housing  102  before activation, and/or to provide resistance or force to aid in breaking the container  120  during activation. As a result, in some embodiments, the base  127  can instead be referred to as “third projections”  127 . 
     As shown in  FIGS. 2-4 , in some embodiments, the insert  130  can be configured to reside entirely in the first chamber  109  of the biological sterilization indicator  100 , such that the insert  130  does not extend into the second chamber  111  where it could potentially interfere with interrogation or detection processes. Furthermore, the insert  130  can be configured to inhibit movement of other portions of the biological sterilization indicator  100  (e.g., the fractured container  120 ) into the second chamber  111 . 
     The insert  130  illustrated in  FIGS. 2-4  is generally symmetrical about a central longitudinal line of symmetry, such that there are two identical first projections  158 , two identical second projections  161 , and two identical third projections  127 . However, the insert  130  need not include any lines of symmetry, and the first projections  158  need not be the same as one another, the second projections  161  need not be the same as one another, and the third projections  127  need not be the same as one another. The insert  130 , and the various projections  158 ,  161  and  127  can be sized and positioned to control the sterilant path  164 , for example, to tailor the kill/survival rate of the biological sterilization indicator  100 , to inhibit inadvertent fracture of the container  120 , to facilitate movement of the container  120  in the housing  120 , to mate with or engage the housing  102 , and/or to control the breakage of the container  120 . 
     By way of example only, the insert  130  illustrated in  FIGS. 2-4  is shown as being a unitary device that includes at least the following: means for holding the container  120  before activation, for fracturing the container  120  during activation; for allowing movement of the container  120  in the housing  102 ; for providing a substantially constant sterilant path  164 , for collecting and/or retaining portions of the fractured container  120  after activation (or at least partially inhibiting movement of portions of the fractured container  120  into the second chamber  111  of the housing  102 ); and/or for minimizing diffusion of the spores  115  and/or signals from the second chamber  111  to the upper portion  116  of the housing  102  after activation. However, it should be understood that in some embodiments, the insert  130  can include multiple portions that may not be part of a single, unitary device, and each of the portions can be adapted to do one or more of the above functions. 
     The insert  130  is referred to as an “insert” because in the embodiment illustrated in  FIGS. 2-4 , the device that performs the above functions is a device that can be inserted into the reservoir  103  (and, particularly, the first chamber  109 ) of the housing  102 . However, it should be understood that the insert  130  can instead be provided by the housing  102  itself or another component of the biological sterilization indicator  100  and need not necessarily be insertable into the housing  102 . The term “insert” will be described throughout the present disclosure for simplicity, but it should be understood that such a term is not intended to be limiting, and it should be appreciated that other equivalent structures that perform one or more of the above functions can be used instead of, or in combination with, the insertable insert  130 . Furthermore, in the embodiment illustrated in  FIGS. 2-4 , the insert  130  is both insertable into and removable from the housing  102 , and particularly, into and out of the first portion  104  (and the first chamber  109 ) of the housing  102 . However, it should be understood that even if the insert  130  is insertable into the housing  102 , the insert  130  need not be removable from the housing  102 , but rather can be fixedly coupled to the housing  102  in a manner that inhibits removal of the insert  130  from the housing  102  after positioning the insert  130  in a desired location. 
     In some embodiments, at least a portion of the housing  102 , for example, the lower portion  114  of the housing  102 , can be transparent to an electromagnetic radiation wavelength or range of wavelengths (e.g., transparent to visible light when visible-light optical detection methods are employed), which can facilitate detection of spore growth. That is, in some embodiments, as shown in  FIGS. 2-4 , at least a portion of the housing  102  can include or form a detection window  167 . 
     In addition, in some embodiments, as shown in  FIG. 2 , at least a portion of the housing  102 , for example, the lower portion  114  can include one or more planar walls  168 . Such planar walls  168  can facilitate detection (e.g., optical detection) of spore growth. In addition, in the embodiment illustrated in  FIGS. 1-5 , the wall  108  of the first portion  104  of the housing  102  can include one or more stepped regions, such as the step  123  (described above), a flat-to-round transition, transition zone, or step,  152  (described in greater detail below), and a tapered wall, or step,  170 . The tapered wall  170  can function to reduce the overall thickness and size of the lower portion, or detection portion,  114  of the housing  102 , such that the outer dimensions of the housing  102  are reduced in addition to the inner dimensions. Such a reduction in size and/or thickness of the lower portion  114  of the biological sterilization indicator  100  can facilitate detection. In addition, having one or more features, such as the steps and/or tapered walls  123 ,  152 ,  170  can allow the biological sterilization indicator  100  to be coupled to a reader or detection device (e.g., the well  14  of the reading apparatus  12 ) in only one orientation, such that the biological sterilization indicator  100  is “keyed” with respect to such a device, which can minimize user error and enhance reliability of a detection process. In some embodiments, one or more portions of the biological sterilization indicator  100  can be keyed with respect to a reading apparatus. 
     The biological sterilization indicator of the present disclosure generally keeps the liquid  122  and the spores  115  separate but in relatively close proximity (e.g., within the self-contained biological sterilization indicator  100 ) during sterilization, such that the liquid  122  and the spores  115  can be readily combined after exposure to a sterilization process. The liquid  122  and the spores  115  can be incubated during a detection process (e.g., the reading apparatus  12  can incubate the biological sterilization indicator  100 ), or the biological sterilization indicator  100  can be incubated prior to a detection process. In some embodiments, when incubating the spores with the liquid  122 , an incubation temperature above room temperature can be used. For example, in some embodiments, the incubation temperature is at least about 37° C., in some embodiments, the incubation temperature is at least about 50° C. (e.g., 56° C.), and in some embodiments, at least about 60° C. In some embodiments, the incubation temperature is no greater than about 60° C., in some embodiments, no greater than about 50° C., and in some embodiments, no greater than about 40° C. 
     A detection process can be adapted to detect a detectable change from the spores  115  (e.g., from within the spore reservoir  136 ) or the liquid  122  surrounding the spores  115 . That is, a detection process can be adapted to detect a variety of characteristics, including, but not limited to, electromagnetic radiation (e.g., in the ultraviolet, visible, and/or infrared bands), fluorescence, luminescence, light scattering, electronic properties (e.g., conductance, impedance, or the like, or combinations thereof), turbidity, absorption, Raman spectroscopy, ellipsometry, or the like, or a combination thereof. Detection of such characteristics can be carried out by one or more of a fluorimeter, a spectrophotometer, colorimeter, or the like, or combinations thereof. In some embodiments, such as embodiments that measure fluorescence, visible light, etc., the detectable change is measured by detecting at a particular wavelength. 
     The spores and/or the liquid  122  can be adapted (e.g., labeled) to produce one or more of the above characteristics as a result of a biochemical reaction that is a sign of spore viability. As a result, no detectable change (e.g., as compared to a baseline or background reading) can signify an effective sterilization process, whereas a detectable change can signify an ineffective sterilization process. In some embodiments, the detectable change can include a rate at which one or more of the above characteristics is changing (e.g., increasing fluorescence, decreasing turbidity, etc.). 
     In some embodiments, spore viability can be determined by exploiting enzyme activity. As described in Matner et al., U.S. Pat. No. 5,073,488, entitled “Rapid Method for Determining Efficacy of a Sterilization Cycle and Rapid Read-out Biological Indicator,” which is incorporated herein by reference, enzymes can be identified for a particular type of spore in which the enzyme has particularly useful characteristics that can be exploited to determine the efficacy of a sterilization process. Such characteristics can include the following: (1) the enzyme, when subjected to sterilization conditions which would be sufficient to decrease a population of 1×10 6  test microorganisms by about 6 logs (i.e., to a population of about zero as measured by lack of outgrowth of the test microorganisms), has a residual activity which is equal to “background” as measured by reaction with a substrate system for the enzyme; and (2) the enzyme, when subjected to sterilization conditions sufficient only to decrease the population of 1×10 6  test microorganisms by at least 1 log, but less than 6 logs, has enzyme activity greater than “background” as measured by reaction with the enzyme substrate system. The enzyme substrate system can include a substance, or mixture of substances, which is acted upon by the enzyme to produce a detectable enzyme-modified product, as evident by a detectable change. 
     In some embodiments, the biological sterilization indicator  100  can be assayed in a single-side mode, where the biological sterilization indicator  100  includes only one detection window (e.g., detection window  167  of  FIG. 2 ) that is positioned, for example, near the spores  115 . In some embodiments, however, the biological sterilization indicator  100  can include more than one detection window (e.g., a window formed by all or a portion of both parallel walls  168  of the lower portion  114  of the housing  102 ), such that the biological sterilization indicator  100  can be assayed via more than one detection window. In embodiments employing multiple detection windows, the detection windows can be positioned side-by-side (similar to a single-side mode), or the detection windows can be oriented at an angle (e.g., 90 degrees, 180 degrees, etc.) with respect to one another. 
     In general, the spores  115  are positioned within the spore reservoir  136  which is in fluid communication with the reservoir  103 . In some embodiments, the spore reservoir  136  forms a portion of the reservoir  103  (e.g., a portion of the second chamber  111 ). As shown in  FIG. 3 , the reservoir  103  is in fluid communication with ambience (e.g., via the aperture  107 ) during sterilization to allow sterilant to enter the reservoir  103  during a sterilization process to sterilize the spores  115 . The container  120  can be configured to contain the liquid  122  during sterilization to inhibit the liquid  122  from being in fluid communication with the spores  115 , the reservoir  103 , and the sterilant during sterilization. 
     Various details of the spores  115  and/or spore reservoir  136  will now be described in greater detail. 
     In some embodiments, the spores  115  can be positioned directly in the lower portion  114  of the housing  102 , or the spores  115  can be positioned in a spore reservoir, such as the spore reservoir  136  (e.g., provided by the spore carrier  135  in the embodiment illustrated in  FIGS. 2-4 ). Whether the spores  115  are positioned directly in the lower portion  114  of the housing  102  or in a spore reservoir, the spores  115  can be provided in a variety of ways. In some embodiments, the spores  115  can be in a spore suspension that can be positioned in a desired location in the biological sterilization indicator  100  and dried down. In some embodiments, the spores  115  can be provided on a substrate (not shown) that can be positioned and/or secured in a desired location in the biological sterilization indicator  100 . Some embodiments can include a combination of spores  115  provided in a dried down form and spores  115  provided on a substrate. 
     In some embodiments, the substrate can be positioned to support the spores  115  and/or to help maintain the spores  115  in a desired locus. Such a substrate can include a variety of materials, including, but not limited to, paper, a polymer (e.g., any of the polymers listed above with respect to the housing  102 ), an adhesive (e.g., acrylate, natural or synthetic rubber, silicone, silicone polyurea, isocyanate, epoxy, or combinations thereof), a woven cloth, a nonwoven cloth, a microporous material (e.g., a microporous polymeric material), a reflective material (e.g., a metal foil), a glass, a porcelain, a ceramic, a gel-forming material (e.g., guar gum), or combinations thereof. In addition, or alternatively, such a substrate can include or be coupled to a hydrophilic coating to facilitate bringing the liquid  122  into intimate contact with the spores  115  (e.g., when the liquid  122  employed is aqueous). In addition, or alternatively, such a hydrophilic coating can be applied to any fluid path positioned to fluidly couple the liquid  122  and the spores  115 . In some embodiments, in addition to, or in lieu of a hydrophilic coating, a hydrophobic coating can be applied to other portions of the housing  102  (e.g., the lower portion  114  of the housing  102 ) and/or spore reservoir  136 , such that the liquid  122  is preferentially moved into contact with the spores  115 . 
     Some embodiments of the biological sterilization indicator  100  do not include the spore carrier  135 . Rather, the spore reservoir  136  is provided by the lower portion  114  of the housing  102  itself, and the spores  115  can be positioned in the lower portion  114 , adsorbed to an inner surface or wall of the lower portion  114 , or combinations thereof. In some embodiments, the spores  115  can be provided on a substrate that is positioned in the lower portion  114  of the housing  102 . 
     In some embodiments, the spores  115  can be positioned in one locus of spores or in a plurality of loci of spores, all of which can be positioned either in the reservoir  103 , in the lower portion  114  of the housing  102 , and/or in the spore reservoir  136 . In some embodiments, having multiple loci of spores can maximize the exposure of the spores to sterilant and to the liquid  122 , can improve manufacturing (e.g., placement of the spores can be facilitated by placing each locus of spores in a depression within the biological sterilization indicator  100 ), and can improve detection characteristics (e.g., because spores in the middle of one large locus of spores may not be as easily detected). In embodiments employing a plurality of loci of spores, each locus of spores can include a different, known number of spores, and/or each locus of spores can include different spores, such that a plurality of spore types can be tested. By employing multiple types of spores, the biological sterilization indicator  100  can be used for a variety of sterilization processes and a specific locus of spores can be analyzed for a specific sterilization process, or the multiple types of spores can be used to further test the effectiveness, or confidence, of a sterilization process. 
     In addition, in some embodiments, the biological sterilization indicator  100  can include a plurality of spore reservoirs  136 , and each spore reservoir  136  can include one or more loci of spores  115 . In some embodiments employing a plurality of spore reservoirs  136 , the plurality of spore reservoirs  136  can be positioned in fluid communication with the reservoir  103 . 
     In some embodiments, the spores  115  can be covered with a cover (not shown) adapted to fit in or over the spores  115  and/or the spore reservoir  136 . Such a cover can help maintain the spores within the desired region of the biological sterilization indicator  100  during manufacturing, sterilization and/or use. The cover, if employed, can be formed of a material that does not substantially impede a detection process, and/or which is at least partially transmissive to electromagnetic radiation wavelengths of interest. In addition, depending on the material makeup of the cover, in some embodiments, the cover can facilitate wicking the liquid  122  (e.g., the nutrient medium) along the spores  115 . In some embodiments, the cover can also contain features for facilitating fluid flow into the spore reservoir  136  (or to the spores  115 ), such as capillary channels, hydrophilic microporous fibers or membranes, or the like, or a combination thereof. In addition, in some embodiments, the cover can isolate a signal, or enhance the signal, which can facilitate detection. Such a cover can be employed whether the spores  115  are positioned within the spore reservoir  136  or directly in the lower portion  114  of the housing  102 . In addition, such a cover can be employed in embodiments employing a plurality of loci of spores. The cover can include a variety of materials, including, but not limited to, paper, a polymer (e.g., any of the polymers listed above with respect to the housing  102 ), an adhesive (e.g., acrylate, natural or synthetic rubber, silicone, silicone polyurea, isocyanate, epoxy, or combinations thereof), a woven cloth, a nonwoven cloth, a microporous material (e.g., a microporous polymeric material), a glass, a porcelain, a ceramic, a gel-forming material (e.g., guar gum), or combinations thereof. 
     In some embodiments, the biological sterilization indicator  100  can further include a modified inner surface, such as a reflective surface, a white surface, a black surface, or another surface modification suitable to optimize the optical properties of the surface. A reflective surface (e.g., provided by a metal foil) can be positioned to reflect a signal sent into the spore reservoir  136  from an assaying or detection device and/or to reflect any signal generated within the spore reservoir  136  back toward the assaying device. As a result, the reflective surface can function to improve (e.g., improve the intensity of) a signal from the biological sterilization indicator  100 . Such a reflective surface can be provided by an inner surface of the housing  102 ; a material coupled to the inner surface of the housing  102 ; an inner surface the spore reservoir  136 ; a material coupled to the inner surface of the spore reservoir  136 ; or the like; or the reflective surface can form a portion of or be coupled to a spore substrate; or a combination thereof. 
     Similarly, in some embodiments, the biological sterilization indicator  100  can further include a white and/or black surface positioned to increase and/or decrease a particular signal sent into the spore reservoir  136  from an assaying device and/or to increase and/or decrease a particular signal generated within the spore reservoir  136 . By way of example only, a white surface can be used to enhance a signal, and a black surface can be used to reduce a signal (e.g., noise). 
     In some embodiments, the spores  115  can be positioned on a functionalized surface to promote the immobilization of the spores  115  on the desired surface. For example, such a functionalized surface can be provided by an inner surface of the housing  102 , an inner surface of the spore reservoir  136 , can form a portion of or be coupled to a spore substrate, or the like, or a combination thereof. 
     In some embodiments, the spores  115  are positioned (e.g. applied by coating or another application method) on a microstructured or microreplicated surface (e.g., such microstructured surfaces as those disclosed in Halverson et al., PCT Publication No. WO 2007/070310, Hanschen et al., US. Publication No. US 2003/0235677, and Graham et al., PCT Publication No. WO 2004/000569, all of which are incorporated herein by reference). For example, such a microstructured surface can be provided by an inner surface of the housing  102 , can be provided by an inner surface of the spore reservoir  136 , can form a portion of or be coupled to a spore substrate, or the like, or a combination thereof. 
     In some embodiments, the biological sterilization indicator  100  can further include a gel-forming material positioned to be combined with the spores  115  and the liquid  122  when the liquid  122  is released from the container  120 . For example, the gel-forming material can be positioned near the spores  115  (e.g., in the spore reservoir  136 ), in the lower portion  114  of the housing  102 , can form a portion of or be coupled to a spore substrate, or the like, or a combination thereof. Such a gel-forming material can form a gel (e.g., a hydrogel) or a matrix comprising the spores and nutrients when the liquid  122  comes into contact with the spores. A gel-forming material (e.g., guar gum) can be particularly useful because it has the ability to form a gel upon hydration, it can aid in localizing a signal (e.g., fluorescence), it can anchor the spores  115  in place, it can help minimize diffusion of the spores  115  and/or a signal from the spore reservoir  136 , and/or it can enhance detection. 
     In some embodiments, the biological sterilization indicator  100  can further include an absorbent or a wicking material. For example, the wicking material can be positioned near the spores  115  (e.g., in the spore reservoir  136 ), can form at least a portion of or be coupled to a spore substrate, or the like, or a combination thereof. Such a wicking material can include a porous wicking pad, a soaking pad, or the like, or a combination thereof, to facilitate bringing the liquid  122  into intimate contact with the spores. 
     In some embodiments, the frangible container  120  can be configured to facilitate fracturing of the frangible container  120  in a desired manner. For example, in some embodiments, a lower portion of the frangible container  120  can be formed of a thinner and/or weaker material, such that the lower portion preferentially fractures over another portion of the frangible container  120 . In addition, in some embodiments, the frangible container  120  can include a variety of features positioned to facilitate fracturing of the frangible container  120  in a desired manner, including, but not limited to, a thin and/or weakened area, a score line, a perforation, or the like, or combinations thereof. 
     The frangible container  120  can have a first closed state in which the liquid  122  is contained within the frangible container  120  and a second open state in which the frangible container  120  has fractured and the liquid  122  is released into the reservoir  103  and/or the spore reservoir  136 , and in fluid communication with the spores  115 . 
     In some embodiments, the biological sterilization indicator  100  can be activated (e.g., the second portion  106  can be moved to the second position  150 ) manually. In some embodiments, the biological sterilization indicator  100  can be activated by the reading apparatus  12  (e.g., as the biological sterilization indicator  100  is positioned in the reading apparatus  12 ). In some embodiments, the biological sterilization indicator  100  can be activated with a device (e.g., an activation device) independent of the reading apparatus  12 , for example, by positioning the biological sterilization indicator  100  in the device prior to positioning the biological sterilization indicator  100  in a well  14  of the reading apparatus  12 . In some embodiments, the biological sterilization indicator  100  can be activated by a combination of two or more of the reading apparatus  12 , a device independent of the reading apparatus  12 , and manual activation. 
     One or both of the biological sterilization indicator  100  and another device, such as the reading apparatus  12  can be further configured to inhibit premature or accidental fracturing of the frangible container  120 . For example, in some embodiments, the biological sterilization indicator  100 , activation device, or reading apparatus  12  can include a lock or locking mechanism that is positioned to inhibit the second portion  106  of the housing  102  from moving into the second position  150  until desired. In such embodiments, the biological sterilization indicator  100  cannot be activated until the lock is moved, removed or unlocked. In addition, or alternatively, in some embodiments, the biological sterilization indicator  100 , activation device, and/or reading apparatus  12  can include a lock or locking mechanism that is positioned to inhibit the second portion  106  of the housing  102  from moving from the second position  150  back into the first position  148  after activation. 
     In some embodiments, as shown in  FIGS. 2-4 , at least a portion of the housing can be flat (e.g., the parallel walls  168 ), and can be substantially planar with respect to the spore reservoir  136 , and one or both of the parallel walls  168  or a portion thereof (e.g., the detection window  167 ) can be sized such that at least one dimension of the wall  168  (or detection window  167 ) substantially matches at least one dimension of the spore reservoir  136  and/or the locus of spores  115 . Said another way, the wall  168  or a portion thereof (e.g., the detection window  167 ) can include a cross-sectional area that is substantially the same size as the cross-sectional area of the spore reservoir  136  and/or the locus of spores  115 . Such size matching between the wall  168 /detection window  167  and the spore reservoir  136  and/or the locus of spores  115  can maximize the signal detected during a detection or assaying process. Alternatively, or in addition, the wall  168  or detection window  167  can be sized to match the reservoir  103  (e.g., at least one dimension or the cross-sectional areas can be sized to match). Such size matching between detection zones can improve spore assaying and detection. 
     The biological sterilization indicator  100  illustrated in  FIGS. 2-4 , at least the portion of the biological sterilization indicator  100  where the spores  115  are positioned, is relatively thin (i.e., the “z dimension” is minimized), such that an optical path from the spores to the wall  168  (or detection window  167 ) is minimized and/or any effect of interfering substances in the liquid  122  (or nutrient medium) is minimized. 
     In use, the biological sterilization indicator  100  can be placed along with a sterilizing batch for a sterilization process. During sterilization, a sterilant is in fluid communication with the reservoir  103  (i.e., the first chamber  109  and the second chamber  111 ), the spore reservoir  136 , and the spores  115  primarily via the sterilant path  164 , such that sterilant can reach the spores to produce sterilized spores. In addition, during sterilization, the frangible container  120  is in a closed state, held intact at least partially by the carrier  132  of the insert  130 . When the frangible container  120  is in a closed state, the liquid  122  is protected from the sterilant and is not in fluid communication with the reservoir  103  (particularly, the second reservoir  111  formed at least partially by the lower portion  114  of the housing  102 ), the spore reservoir  136 , the spores  115 , or the sterilant path  164 . 
     Following sterilization, the effectiveness of the sterilization process can be determined using the biological sterilization indicator  100 . The second portion  106  of the housing  102  can be unlocked, if previously locked in the first position  148 , and moved from the first position  148  (see  FIG. 3 ) to the second position  150  (see  FIG. 4 ) to cause activation of the biological sterilization indicator  100 . Such movement of the second portion  106  can cause the frangible container  120  to move in the housing  102 , for example, along the longitudinal direction D L  from a position above the upper ends  159  of the projections  158  to a position within the interior of the projections  158 , which can cause the frangible container  120  to fracture. Fracturing the frangible container  120  can change the frangible container  120  from its closed state to its open state and release the liquid  122  into the reservoir  103 , and into fluid communication with the spore reservoir  136  and the spores  115 . The liquid  122  can either include nutrient medium (e.g., germination medium) for the spores, or the liquid  122  can contact nutrient medium in a dry form (e.g., in a powdered or tablet form) to form nutrient medium, such that a mixture including the sterilized spores and nutrient medium is formed. The mixture can then be incubated prior to or during a detection or assaying process, and the biological sterilization indicator  100  can be interrogated for signs of spore growth. 
     To detect a detectable change in the spores  115 , the biological sterilization indicator  100  can be assayed immediately after the liquid  122  and the spores  115  have been combined to achieve a baseline reading. After that, any detectable change from the baseline reading can be detected. The biological sterilization indicator  100  can be monitored and measured continuously or intermittently. In some embodiments, a portion of, or the entire, incubating step may be carried out prior to measuring the detectable change. In some embodiments, incubation can be carried out at one temperature (e.g., at 37° C., at 50-60° C., etc.), and measuring of the detectable change can be carried out at a different temperature (e.g., at room temperature, 25° C., or at 37° C.). 
     The readout time of the biological sterilization indicator  100  (i.e., the time to determine the effectiveness of the sterilization process) can be, in some embodiments, less than 8 hours, in some embodiments, less than 1 hour, in some embodiments, less than 30 minutes, in some embodiments, less than 15 minutes, in some embodiments, less than 5 minutes, and in some embodiments, less than 1 minute. 
     Biological Sterilization Indicator System 
     The biological sterilization indicator system  10  will now be described with reference to  FIGS. 3-5 .  FIGS. 3 and 4  illustrate the biological sterilization indicator system  10  of  FIG. 1  in cross-section, taken along line  3 - 3  of  FIG. 1 , and  FIG. 5  illustrates a block diagram of one embodiment of the reading apparatus  12 . 
     The phrase “reading apparatus” generally refers to one or more devices that operate to “read” a biological sterilization indicator  100  to detect whether the spores  115  of the biological sterilization indicator  100  survived a sterilization process, as a means of judging the efficacy of a sterilization process. The phrase “reading apparatus” is meant to encompass any combination of mechanical and electronic components necessary to perform such a detection. In addition, in the present disclosure, the reading apparatus  12 , or a portion thereof, is configured to detect whether the biological sterilization indicator  100  has been activated. As a result, a first device, or portion of the reading apparatus  12 , can be dedicated to determining an activation status of the biological sterilization indicator  100 , and a second device, or another portion of the reading apparatus  12 , can be dedicated to determining the efficacy of a sterilization process. When more than one device is employed as the reading apparatus  12 , the devices need not be directly coupled together. As a result, even though the phrase “reading apparatus” is used throughout as being configured to detect activation and sterilization efficacy, it should be understood that such a disclosure also includes when a first device, or reading apparatus, is used to detect activation, and a second device, or reading apparatus, is used to detect sterilization efficacy. However, particular advantages can be found when one single device is used to detect both activation and sterilization efficacy. 
     As shown in  FIG. 5 , in some embodiments, the reading apparatus  12  can synchronously process multiple biological sterilization indicators  100  without user intervention. In addition, the reading apparatus  12  can combine the incubation site and reader site to a common location. Fluorescence values can be read for each well  14  independently. As shown in  FIGS. 3-5 , in some embodiments, the reading apparatus  12  can include an incubator block  21 , which can maintain stable and consistent temperature for incubation of biological sterilization indicators  100  in multiple wells  14 . By way of example only, the reading apparatus  12  is illustrated as including ten wells  14  that can each independently process a biological sterilization indicator  100 . Each well  14  of the reading apparatus  12  can include a corresponding display area (e.g., an LCD display) on the display  16  of the reading apparatus  12  to display biological sterilization indicator processing results to a user, well  14  number, time remaining, temperature, and/or other general information. 
     As shown in  FIGS. 3 and 4 , in some embodiments, the incubator block  21  can be dimensioned and shaped (e.g., “keyed”) to accommodate the shape of the biological sterilization indicator  100 , or a portion thereof (e.g., especially the outer shape of the lower portion  114  of the biological sterilization indicator  100 ). Such a design of the incubator block  21  can allow stable and consistent incubation of the biological sterilization indicator  100 , which can allow for stable assay or interrogation results (e.g., stable fluorescence readings), while still allowing the biological sterilization indicator  100  to present an unobstructed detection window  167  (e.g., a flat detection window  167 ) to the optics/detection system(s) of the reading apparatus  12  (e.g., the second sensor  54 , described in greater detail below). 
     In some embodiments, the incubator block  21  can be one integrally formed component, with an individual portion or section configured to interact independently with each well  14  of the reading apparatus  12 . In some embodiments, each well  14  can be equipped with its own, independent and separate incubator block  21 . No matter the mechanical configuration of the incubator block(s)  12  for the entire reading apparatus  12 , each incubator block  21  that corresponds to a well  14  of the reading apparatus  12  can be operated independently of adjacent incubator blocks  21  and can be thermally isolated and insulated from such adjacent incubator blocks  21 , as needed (e.g., via an air gap). 
     In some embodiments, the reading apparatus  12  can include three printed circuit board assemblies (PCBAs), namely, a main PCBA  45 , a light-emitting diode (LED) PCBA  47 , and a biological sterilization indicator (BSI) detector PCBA  49 .  FIG. 5  shows a breakdown of the primary circuit modules within the main PCBA  45 . The main PCBA  45  can provide the control functions for the LED PCBA  47  and the BSI detector PCBA  49 , as well as the display  16  and heater (e.g., a resistive flexible heater), and can coordinate their interactions and dependencies. The heater can be thermally coupled to the incubator block  21 , which can be thermally coupled to one or more wells  14  of the reading apparatus  12 . 
     In embodiments employing ten wells  14 , the LED PCBA  47  can house ten LEDs (e.g., UV LEDs)—one for each sample well  14 . The LEDs can serve as an excitation source for a biological sterilization indicator  100 . The BSI detector PCBA  49  can include ten first sensors  52 , which can be used to detect the presence of a biological sterilization indicator  100  in a corresponding well  14 , as well as the approximate position of the second portion  106  of the biological sterilization indicator  100 , as described in greater detail below. 
     As shown in  FIG. 5 , in some embodiments, the main PCBA  45  can include three microcontrollers: a main microcontroller  60 , an optics microcontroller  62 , and a display microcontroller  64 . The three microcontrollers  60 ,  62  and  64  can collectively be referred to as the “controller”  51  of the reading apparatus  12 . 
     The controller  51 , shown schematically in  FIGS. 3 and 4 , can be configured to control the various processing and executing portions of the reading apparatus  12 . Generally, the controller  51  (or microcontrollers  60 ,  62  and  64 ) can be a suitable electronic device, such as, for example, a programmable logic controller (“PLC”), a microprocessor, a personal computer (“PC”), another industrial/personal computing device, or combinations thereof. As such, the controller  51  may include both hardware and software components, and is meant to broadly encompass the combination of such components. The controller  51  is only shown schematically in  FIGS. 3 and 4 , but one of ordinary skill in the art will understand the various ways in which components of the reading apparatus  12  can interact with the controller  51 , for example, via wired or wireless communication. The breakdown of the controller  51  shown in  FIG. 5  is shown by way of example only. 
     The main microcontroller  60  can control an excitation driver circuit  66  for driving excitation sources, such as LEDs, in conjunction with the LED PCBA  47 . The excitation driver circuit  66  can include a ten-channel constant current driver in which each channel is controlled individually, and can connect to an array of LEDs (e.g., UV LEDs) on the LED PCBA  47 . Each channel of the ten-channel current driver can be calibrated/normalized to accommodate variations from channel to channel. The main microcontroller  60  can also detect insertion and/or activation of biological sterilization indicators  100  by controlling BSI detection circuits  73  (e.g., which can include ten circuits in embodiments employing ten wells  14 ), in conjunction with the BSI detector PCBA  49 . The BSI detection circuits  73  can each include a sensor, such as a proximity sensor (e.g., the first sensors  52 , described in greater detail below with reference to  FIGS. 3 and 4 ), that can allow the main microcontroller  60  to monitor the insertion or removal of biological sterilization indicators  100  relative to a corresponding well  14 , as well as the detection of activation of the biological sterilization indicators  100 . The main microcontroller  60  can also obtain emission readouts from the optics microcontroller  62 ; control the display microcontroller  64 , and communicate with a host computer  68  via an Ethernet communication  69 . 
     The optics microcontroller  62  can provide control of detection circuits  75  (e.g., which can include ten circuits in embodiments employing ten wells  14 ). Such detection circuits  75  can each include a detector, such as a photodiode, (e.g., a detector  74  of a second sensor  54 , as described in greater detail below, with reference to  FIGS. 3 and 4 ). The optics microcontroller  62  can also provide control of the temperature of the incubation block  21  via a heater control  76 . The heater control  76  can include a closed-loop system that monitors the temperature of the incubator block  21  and turns the incubator block  21  on and off accordingly. 
     Furthermore, in some embodiments, the reading apparatus  12  (e.g., the optics microcontroller  62 ) can be adapted to minimize the effects of temperature variation on various electronic components of the reading apparatus  12 , such as the detection circuits  75  (e.g., for fluorescence detection). That is, in some embodiments, temperature variations of various optical components can be determined and eliminated. In such embodiments, the temperature of various optical components and/or ambient temperature can be monitored, a correction factor can be determined, and the correction factor can be used to normalize the output from such optical components (e.g., the detectors  74  of the detection circuits  75 ). Such adjustments can minimize fluctuations in output that may be the result of temperature variation, and can improve the accuracy of the assay results of the reading apparatus  12  (e.g., regarding sterilization efficacy). 
     The display microcontroller  64  can receive information from the main microcontroller  60 , can generate character sets, and can display information and/or capture information from the display and/or user interface  16 . The display  16  can display status information and can provide error codes to a user. 
     As further shown in  FIGS. 3 and 4 , the reading apparatus  12  can include a dedicated detection system  55  associated with each of the wells  14  of the reading apparatus  12 . In some embodiments, a detection system  55  can be associated with (e.g., receive signals from, deliver electromagnetic radiation to, and/or generally interact with) more than one well  14  of the reading apparatus  12 ; however, particular benefits have been observed when each well  14  of the reading apparatus  12  is associated with an independent and dedicated detection system  55 . The dedicated detection system  55  can include all or a portion of the BSI detection circuits  73 , the excitation driver circuit  66 , and/or the detection circuits  75 . 
     In  FIGS. 3 and 4 , one well  14 , one biological sterilization indicator  100  and one detection system  55  are shown in cross-section. As shown, in some embodiments, the detection system  55  can include a first sensor  52  positioned to be aligned with the signal-modulating feature  153  of the first portion  104 , and a second sensor  54 . The first sensor  52  can be calibrated by zeroing out ambient light. In some embodiments, the first sensor  52  can be positioned to detect the presence of the biological sterilization indicator  100  in the well  14 , as well as the position of the second portion  106  of the biological sterilization indicator  100  (e.g., to confirm activation of the biological sterilization indicator  100 ). In some embodiments, the second sensor  54  can be used to confirm that the biological sterilization indicator  100  has been properly positioned (e.g., fully seated) within the well  14  (e.g., to reliably confirm activation), and/or to perform the detection or assaying process by interrogating the lower portion  114  (or the second chamber  111 , or a portion thereof) of the housing  102  for spore growth, for example, for a detectable change in the spores  115  or in the liquid surrounding the spores  115 . In some embodiments, the first sensor  52  alone is used to confirm activation of the biological sterilization indicator  100 . 
     At least partly because of the design of the biological sterilization indicator  100 , the well  14  of the reading apparatus  12 , and the second sensor  54 , the entire lower portion  114  of the biological sterilization indicator  100  can be interrogated by the second sensor  54 , which can result in a faster positive (e.g., spore viability and sterilization cycle failure) result than existing systems. Each well  14  can be independently interrogated by its own corresponding dedicated detection system  55  (e.g., an optical detection system). In some embodiments, the reading apparatus  12  can include one or more baffles positioned to inhibit cross-talk between the wells  14 . 
     In some embodiments, the reading apparatus  12  can include a plurality of parts or elements that can be coupled together to define at least a portion of the well(s)  14  and/or to house the detection systems  55  (e.g., including the first sensors  52 , the excitation sources  72  and the detectors  74 ). As shown in  FIGS. 3 and 4  by way of example only, the reading apparatus  12  can include a first frame element  80  dimensioned to receive the incubator block(s)  21 , and a second frame element  82  dimensioned to receive the excitation source(s)  72  and the detector(s)  74 . As shown in  FIGS. 3, 4, 11 and 12 , the first and second frame elements  80  and  82  can be configured to be coupled together or to have mating, inter-engaging, or cooperating parts. In addition, in some embodiments, the reading apparatus  12  can further include a third frame element  84 , which can couple to at least one of the first and second frame elements  80  and  82 , and particularly, which can form a cover for the second frame element  82 . 
     As shown in  FIGS. 11 and 12 , which show a horizontal and vertical cross-section planes through the reading apparatus  12  (with the biological sterilization indicator  100  not shown for clarity), in some embodiments, one or more of the incubator block  21 , the first frame element  80 , the second frame element  82 , and the third frame element  84  can include one or more protrusions, recesses, or ribs that are configured to interact with a mating part of an adjacent component (e.g., with one or more of the incubator  21  and the frame elements  80 ,  82  and  84 ) to form one or more baffles that are positioned between adjacent wells  14  in order to inhibit cross-talk of electromagnetic radiation (e.g., visible and/or ultraviolet light) between the wells  14 . 
     With reference to  FIGS. 11 and 12 , in some embodiments, the incubator block  21  can include a plurality of channels  86  that extend along an upper surface, a bottom surface, and a side surface of the incubator block  21 . In addition, the first frame element  80  can include a plurality of protrusions or ribs  88 , each of which is dimensioned to be received in a channel  86  of the incubator block  21 . While the channel(s)  86  and corresponding rib(s)  88  are shown in the illustrated embodiment as extending continuously along three sides or edges of the incubator block(s)  21  and the first frame element  80 , it should be understood that in some embodiments, only one or more discrete channels(s)  86  and ribs(s)  88  may be necessary, which may be located on one or more sides or edges of the incubator block(s)  21  and/or the first frame element  80 . 
     With continued reference to  FIG. 11 , in some embodiments, the first frame element  80  can further include a plurality of channels  90  that are formed in a rear surface. The second frame element  82  can include a plurality of protrusions or ribs  92 , each of which is dimensioned to be received in a channel  90  of the first frame element  80 . Similar additional coupling between the second frame element  82  and the third frame element  84  can also be present. In addition, as shown in  FIG. 11 , in some embodiments, the first frame element  80  and the incubator block  21  can at least partially define a plurality of wells  14 , and the second frame element  82  can include one or more recesses aligned with a well  14  that are configured to house an excitation source  72  and/or a detector  74  dedicated to the adjacent well  14 . For example, as shown in  FIG. 11 , in some embodiments, the second frame element  82  can include a plurality of first recesses  94 , each of which is adapted to house at least a portion of an excitation source  72 , and a plurality of second recesses  96 , each of which is adapted to house at least a portion of a detector  74 . 
     Such coupling of the incubator block  21 , the first frame element  80 , and the second frame element  82  allows for the three components to be coupled together to at least partially define the wells  14 , to at least partially house the excitation sources  72  and the detectors  74  in line with the wells  14 , and to define a first series or plurality of baffles  85  (e.g., defined by one or both of the channels  86  and the ribs  88 ; see  FIGS. 11 and 12 ) and a second series or plurality of baffles  87  (e.g., defined by one or both of the channels  90  and the ribs  92 ) positioned between the wells  14 . Additional baffling can be employed between wells  14  with mating structures between the second frame element  82  and the third frame element  84 . 
     The reading apparatus  12  is shown in  FIGS. 3, 4, 11 and 12  as including an incubator block  21  and three frame elements  80 ,  82  and  84  to at least partially define the wells  14  and baffling structures between wells  14 . However, it should be understood that as few as one frame element or incubator block and as many as necessary can be employed to define the wells  14  and baffling structures. In addition, the channels  86  and  90  and the ribs  88  and  92  can be used interchangeably. For example, in some embodiments, the incubator block  21  can include a plurality of ribs  86  that mate with channels  88 , and so on. Any similar inter-engaging structures can be employed to create one or more baffles  85 ,  87  to inhibit cross-talk between the wells  14  without departing from the spirit and scope of the present disclosure. Furthermore, in some embodiments, the reading apparatus  12  can include only one series of baffles, rather than at least two (i.e., the baffles  85  and  87 ). 
     As described above, in some embodiments, sufficient closure of the second portion  106  with respect to the first portion  104  of the biological sterilization indicator (e.g., sufficient cap closure) can be indicative of a successful activation step. In such embodiments, the reading apparatus  12  can include means for detecting the position of the second portion  106 . For example, the first sensor  52  can be positioned to detect at least one of the following: (i) when the well  14  corresponding to the first sensor  52  is empty, and output a first signal; (ii) when the biological sterilization indicator  100  is positioned in the well  14  and the second portion  106  is in the first position  148 , or at least is not in the second position  150 , and output a second signal; and (iii) when the biological sterilization indicator  100  is positioned in the well  14  and the second portion  106  is in the second position  150 . The controller  51  of the reading apparatus  12  can receive the first signal, the second signal, or the third signal, and execute varying actions based on which signal is received. 
     As mentioned above, in some embodiments, the second position  150  of the second portion  106  can be any position in which the seal  156 , or a portion thereof, engages a portion (e.g., the upper end  157 ) of the first portion  104  of the housing  102 . As a result, the reading apparatus  12  (e.g., the controller  51 ) can include a threshold value that the third signal would need to reach in order to register the second portion  106  as being in a “second position,” for example, in which the seal  156  is engaged and the interior of the biological sterilization indicator  100  is sealed from ambience. Such a threshold can accommodate different levels or degrees of closure of the second portion  106 . For example, in some embodiments, even when only an edge (e.g., a lower edge) of the second portion  106  is in line with the first sensor  52 , or “visible” to the first sensor  52 , the threshold can be met, the first sensor  52  can send the third signal to the controller  51 , and sufficient activation and sealing of the biological sterilization indicator  100  can be confirmed. This could be the case, for example, when the seal  156  is sized (e.g., has a sufficient length in the longitudinal direction D L  of the biological sterilization indicator  100 ) and the threshold value is controlled such that when the threshold is met, the seal  156  is engaged. On the other hand, in embodiments in which the seal  156  is not sufficiently engaged when only an edge of the second portion  106  is in line with the first sensor  52 , the threshold value can be adjusted such that the third signal would not be sent to the controller  51  until the second portion  106  is moved further onto the first portion  104  to generate a signal that meets or exceeds the threshold value. 
     If the controller  51  receives the first signal from the first sensor  52 , the controller  51  can output to the display  16  an error code or some level of output to indicate to an operator that the well  14  is empty. Similarly, if the controller  51  receives the second signal from the first sensor  52 , the controller  51  can output to the display  16  an error code or some level of output to indicate to an operator that a biological sterilization indicator  100  is positioned in the respective well  14 , but that the second portion  106  is not in the second position  150 , or that the biological sterilization indicator  100  has not been activated. If the controller  51  receives the third signal from the first sensor  52 , the controller  51  can begin to initiate a spore growth and/or detection process, or the assay result will be output to the display  16  without an error code. 
     In some embodiments, the reading apparatus  12  can detect and generate (e.g., the controller  51  can output) only the first signal (i.e., the well  14  is empty) and the third signal (i.e., the biological sterilization indicator  100  is activated). In some embodiments, however, the reading apparatus  12  can generate the first signal, the second signal, and the third signal. As a result, in some embodiments, the reading apparatus  12  can generate at least two of the first signal, the second signal, and the third signal. 
     As mentioned above, the biological sterilization indicator  100  can be activated while the biological sterilization indicator  100  is positioned in the well  14  of the reading apparatus  12 ; prior to being positioned in the well  14 ; and/or as the biological sterilization indicator  100  is positioned in the well  14  by depressing the second portion  106  as the biological sterilization indicator  100  becomes seated in the well  14 . The biological sterilization indicator  100  can be activated manually (e.g., prior to, during or after being inserted into the well  14  of the reading apparatus  12 ), or by using an activation device (e.g., by positioning the biological sterilization indicator  100  into a device separate from the reading apparatus  12 ). 
     In some embodiments, whether the biological sterilization indicator  100  is activated in the well  14  or out of the well  14 , the reading apparatus  12  can be configured to determine if the second portion  106  is in the second position  150 , and not to initiate a spore growth and assay process until activation of the biological sterilization indicator  100  is confirmed. In some embodiments, however, the reading apparatus  12  can perform the spore growth and/or detection process, but an error code or some level of output can be given to a user to inform the user that the biological sterilization indicator  100  is not properly positioned in the well  14 , the biological sterilization indicator  100  has not been activated, that the spore growth and/or detection process could not be completed, that the spore growth and/or detection process could not be initiated, that the assay result may be questionable, or the like, or a combination thereof. Such error codes or outputs from the reading apparatus  12  can be displayed in the display  16  of the reading apparatus  12 . 
     In some embodiments, the detection process (e.g., which can be controlled by the optics microcontroller  62  and can include operation of the detection circuits  75 ) for verifying the efficacy of a sterilization process can employ fluorescence detection in order to interrogate the second chamber  111 , or a portion thereof. For example, as shown in  FIGS. 3 and 4 , in some embodiments, the second sensor  54  can be adapted for fluorescence detection and can include at least one emitter or excitation source (e.g., a light-emitting diode (LED))  72  configured and positioned to emit electromagnetic radiation at a specific frequency or range of frequencies, and a detector (e.g., an emissions detector, such as a photodiode)  74  configured and positioned to detect certain frequencies of electromagnetic radiation emitted from the second chamber  111 , or a portion thereof. The acute angle between the excitation source  72  and the detector  74  is shown by way of example only; however, it should be understood that other configurations are possible, including, but not limited to, a right angle, an obtuse angle, a through-path (e.g., 180 degrees) configuration, etc., or combinations thereof. Various filters known to those of ordinary skill in the art can be employed to achieve the desired frequency emission and/or detection. The excitation source  72  can excite various fluorescent molecules with a first frequency of electromagnetic radiation which can cause the fluorescent molecules to fluoresce and emit electromagnetic radiation at a second frequency, which can then be detected by the detector  74  of the second sensor  54 . Other details of fluorescence detection generally known to those of ordinary skill in the art can be employed. 
     As mentioned above, in some embodiments, at least a portion of the second sensor  54  can be used to confirm that the biological sterilization indicator  100  has been properly positioned (e.g., fully seated) within the well  14 . That is, in some embodiments, as shown in  FIGS. 3 and 4 , the first sensor  52  can be positioned toward the top of the well  14  and adjacent a location on the biological sterilization indicator  100  where the second portion  106  will reside when in the second position  150 . In such embodiments, the first sensor  52  can detect whether an upper portion (or region)  15  of the well  14  is empty, but when the upper portion  15  is not empty, the first sensor  52  may not be able to confirm that a lower portion (or region)  17  of the well  14  is not empty. That is, as mentioned above, in some embodiments, the biological sterilization indicator  100  and the well  14  can be “keyed” with respect to one another, such that the biological sterilization indicator  100  can be positioned in the well  14  in only one orientation. If the biological sterilization indicator  100  is positioned in the well  14  at an incorrect orientation (e.g, incorrectly turned around about the longitudinal direction D L ), the first sensor  52  may detect that the upper portion  15  of well  14  is not empty, but the biological sterilization indicator  100  may not be fully seated within the well  14 . In such embodiments, the first sensor  52  may not be properly aligned with and able to detect any signal-modulating features  153  either of the first portion  104  or the second portion  106 . In such cases, at least a portion of the second sensor  54  can be used to confirm that the biological sterilization indicator  100  is positioned in the lower portion  17  of the well  14 . As shown in  FIGS. 3  and  4 , the second sensor  54  can be positioned toward the bottom of the well  14  (i.e., adjacent the lower portion  17  of the well  14 ) and can be positioned to detect whether the lower portion  17  of the well  14  is empty. 
     In some embodiments, as shown in  FIGS. 3 and 4 , the well  14  can be elongated and can include a longitudinal direction. The longitudinal direction D L  of the biological sterilization indicator  100  can be oriented substantially along (or substantially aligned with) the longitudinal direction of the well  14  when the biological sterilization indicator  100  is positioned in the well  14 . In such embodiments, the upper portion  15  of the well  14  can be a first longitudinal portion or region  15 , and the lower portion  17  of the well  14  can be a second longitudinal portion or region  17  that is spaced a longitudinal distance from the first longitudinal portion or region  15 . 
     In such embodiments, the second sensor  54  can be configured to generate a fourth signal indicative of the lower portion  17  of the well  14  being empty, and a fifth signal indicative of the lower portion  17  of the well  14  not being empty. In some embodiments, the second sensor  54  can be configured to generate a sixth signal indicative of the liquid  122  being present in the lower portion  114  of the biological sterilization indicator  100 . Examples of systems designed to detect the presence of fluid in a specific chamber or region of the biological sterilization indicator are described in co-pending U.S. Application No. 61/408,997. In some embodiments, the second sensor  54  can be configured to generate a sixth signal (or a seventh signal, if the liquid detection function is employed) indicative of spore viability (i.e., sterilization cycle failure) and a seventh signal (or an eighth signal, if the liquid detection function is employed) indicative of spore death (i.e., sterilization cycle success). 
     In embodiments employing the second sensor  54  to additionally confirm proper positioning of the biological sterilization indicator  100  in the well  14  in order to rely on the signal from the first sensor  52  to confirm activation, in some embodiments, the reading apparatus  12  can initiate a spore growth procedure (or simply not report error codes when the assay results are displayed) when the controller  51  receives the third signal from the first sensor  52  and the fifth signal from the second sensor  54 . On the other hand, the reading apparatus  12  can either prevent an assay process from initiating, or report error codes when the assay results are displayed, when the controller  51  receives the first signal or the second signal from the first sensor  52  and the fourth signal from the second sensor  54 . The first sensor  52  signals are referred to as the “the first signal,” “the second signal,” and “the third signal,” and the second sensor  54  signals are referred to as “the fourth signal” and “the fifth signal,” etc. for clarity purposes only; however, it should be understood that all signal references are for clarity and simplicity only, and other signal references can be used to describe the outputs generated by the first and second sensors  52  and  54  without departing from the spirit and scope of the present disclosure. 
     As described above, the second sensor  54  can include an excitation source  72  and a detector  74  that can be employed for fluorescence detection, for example, when assaying the biological sterilization indicator  100  for spore viability. In some embodiments, the same excitation source  72  and detector  74  can be used to generate the fourth and/or fifth signals for the purposes of confirming the position of the biological sterilization indicator  100  in the well  14 , and/or of confirming activation of the biological sterilization indicator  100 . While this configuration of the second sensor  54  is shown and described, it should be appreciated to those of ordinary skill in the art that other configurations and types of sensors (e.g., any of those described below with respect to the first sensor  52 ) or components can be employed in the second sensor  54  for the purpose of confirming position and/or activation of the biological sterilization indicator  100 . 
     In some embodiments, the first sensor  52  can include at least one of a photointerrupter (e.g., transmissive and/or reflective), a capacitive sensor, another suitable proximity sensor, or a combination thereof. Photointerrupters can detect an object that interrupts a light beam between a sensor and a reflector (i.e., reflective) or between an emitter and a receiver (i.e., transmissive). As a result, in some embodiments, the first sensor  52  can include an excitation source and detector, similar to that described above with respect to the second sensor  54 . However, in some embodiments, the excitation source and detector of the first sensor  52  can be located near one another, for example, in the same housing. For example, in embodiments employing a reflective photointerrupter, the first sensor  52  can detect the position of the second portion  106  by emitting electromagnetic radiation into an adjacent portion of the well  14 , and sensing the reflected signal. In some embodiments, the first portion  104  and/or the second portion  106  can include one or more signal-modulating features that could modify the signal emitted by the first sensor  52 , such that the modulation of the reflected signal would be detected by the first sensor  52 . A variety of signal-modulating features can be employed with the first portion  104 , the second portion  106 , and/or another component of the biological sterilization indicator  100 . In the embodiment shown in  FIGS. 3 and 4 , the first portion  104  can include a signal-modulating feature  153  that can be used to alter the signal received by the first sensor  52  when the electromagnetic radiation is reflected back to the first sensor  52 . 
     By way of example only, the signal-modulating feature  153  is shown in the embodiment of  FIGS. 1-4  as being or including the flat-to-round transition, or step,  152 . In some embodiments, particularly in those employing reflective sensors, if the first sensor  52  emits a signal into an empty well  14 , the signal that is reflected back to the first sensor  52  will be low, relative to other received (e.g., reflected) signals. Furthermore, if the first sensor  52  emits a signal onto a smooth portion (e.g., a smooth flat surface or a smooth rounded surface) of the first portion  104  or the second portion  106 , the received (e.g., reflected) signal will be high, relative to other signals. On the other hand, if the first sensor  52  detects the flat-to-round transition  152 , the reflected signal received by the first sensor  52  will be intermediate that of the relatively low signal and the relatively high signal, such that substantially and significantly different signals will be received by the first sensor  52 , and will be indicative of different scenarios. 
     With reference to the embodiment of  FIGS. 3 and 4 , if the well  14  is empty, the first sensor  52  will receive a low signal and will send the first signal to the controller  51 . If the biological sterilization indicator  100  is positioned in the well  14  but the second portion  106  is not in the second position  150 , as shown in  FIG. 3 , the first sensor  52  will receive an intermediate signal because at least a portion of the signal emitted by the first sensor  52  will be deflected by the exposed signal-modulating feature  153  (i.e., the flat-to-round transition  152 ) of the first portion  104 . The first sensor  52  will then send the second signal to the controller  51 . However, if the second portion  106  has been moved to the second position  150  (or when the second portion  106  is moved to the second position  150 ), as shown in  FIG. 4 , the first sensor  52  will receive a high signal because the second portion  106  will have moved a sufficient amount to cover or obscure the signal-modulating feature  153  of the first portion  104  from being detected by the first sensor  52 . When the signal-modulating feature  153  is obscured by the second portion  106  and no longer exposed to or aligned with the first sensor  52 , the signal from the first sensor  52  is not deflected by the signal-modulating feature  153 . Rather, the first sensor  52  would receive a relatively high signal from the smooth outer surface of the second portion  106  when the second portion  106  is in the second position  150 . In such embodiments, the reading apparatus  12  can be configured such that the relatively high signal results in the first sensor  52  sending the third signal to the controller  51 , because the biological sterilization indicator  100  is positioned in the well  14  and the second portion  106  has been moved to the second position  150 . 
     That is, in the embodiment illustrated in  FIGS. 1-4 , the first portion  104  of the biological sterilization indicator  100  includes a signal-modulating feature  153  that can be exposed to, accessible by, readable by and/or detectable by the reading apparatus  12  when the second portion  106  is in the first position  148  (or not in the second position  150 ) but not when the second portion  106  is in the second position  150  (i.e., the second portion  106  obscures the signal-modulating feature  153  when in its second position  150 ). As a result, in the embodiment of  FIGS. 1-4 , the first sensor  52  can generate: a first signal when the well  14  is empty; a second signal that is significantly different from the first signal, based on the exposed signal-modulating feature  153  of the first portion  104 , when the biological sterilization indicator  100  is positioned in the well  14  and the second portion  106  of the biological sterilization indicator  100  is not in the second position  150 , e.g., is in the first position  148  (see  FIG. 3 ); and a third signal that is significantly different from the first signal and the second signal, when the biological sterilization indicator  100  is positioned in the well  14 , the second portion  106  is in the second position  150 , and the signal-modulating feature  153  is no longer exposed (see  FIG. 4 ). 
     Additionally, or alternatively, in some embodiments, the second portion  106  can include a signal-modulating feature.  FIG. 6  illustrates a second portion  206  of the housing of a biological sterilization indicator according to another embodiment of the present disclosure. As shown in  FIG. 6 , the second portion  206  can be similar to the second portion  106  of  FIGS. 2-4 , except that the second portion  206  can include a signal-modulating feature  253 . By way of example, the signal-modulating feature  253  includes an inwardly-extending angled surface, wall, or deflection zone  252  located adjacent the bottom edge of the second portion  206 . That is, the angled surface  252  can be adapted to deflect light differently than adjacent portions of the outer surface of the second portion  206 . In some embodiments, the angled surface  252  can be referred to as a recess. Such a signal-modulating feature  253  can be positioned to be sensed by the first sensor  52 , for example, when the second portion  206  is in its second position. 
     Similarly,  FIG. 7  illustrates a second portion  306  of the housing of a biological sterilization indicator according to another embodiment of the present disclosure. As shown in  FIG. 7 , the second portion  306  can be similar to the second portions  106  and  206 , except that the second portion  306  of  FIG. 7  can include a signal-modulating feature  353 . By way of example, the signal-modulating feature  353  includes an outwardly-extending angled surface, wall, or deflection zone  352  located adjacent the bottom edge of the second portion  306 . The angled surface  352  can be adapted to deflect light differently than adjacent portions of the outer surface of the second portion  306 . In some embodiments, the angled surface  352  can be referred to as a protrusion, flange, or ledge. Again, such a signal-modulating feature  353  can be positioned to be sensed by the first sensor  52 , for example, when the second portion  306  is in its second position. 
       FIG. 8  illustrates a second portion  406  of the housing of a biological sterilization indicator according to another embodiment of the present disclosure. As shown in  FIG. 8 , in some embodiments, the second portion  406  can include a signal-modulating feature  453 . By way of example, the signal-modulating feature  453  includes a label  452  or other color or surface modification that presents a signal that is unique to the second portion  406 , e.g., a uniquely high or uniquely low signal (i.e., relative to an empty well or a first portion of a biological sterilization indicator) to the first sensor  52  when the second portion  406  is in its second position. The label  452  can include a color, dye, and/or surface finish that produces the uniquely high or uniquely low signal, for example, relative to a first portion of the housing of a biological sterilization indicator. In addition, or alternatively, the label  452  can include a pattern, barcode, or other identifying feature unique to the second portion  406 , such that the label  452 , or a portion thereof, produces the unique signal, for example, relative to a first portion of the housing of the biological sterilization indicator. In such embodiments, a sensor (e.g., the first sensor  52  of the reading apparatus  12  of  FIGS. 1-5 ) can be configured to align with the label  452 , or a desired portion thereof, when the second portion  406  is in its second, or closed, position, such that the sensor can confirm (i.e., via the signal that is unique to the label  452 ) that the second portion  406  has moved a sufficient amount to cause fracturing of a container, and to cause activation (and/or sealing) of the biological sterilization indicator. In other embodiments, a first portion of the biological sterilization indicator can include such a label that provides a unique signal when the second portion  406  is in its first position but which is obscured by the second portion  406  when the second portion  406  is in its second position. 
     In embodiments such as those shown in  FIGS. 6-8 , the second portion  206 ,  306 ,  406  can include a signal-modulating feature  253 ,  353 ,  453  instead of the first portion  104  including a signal-modulating feature, and the signal-modulating feature  253 ,  353 ,  453  can be positioned on the second portion  206 ,  306 ,  406  such that the signal-modulating feature  253 ,  353 ,  453  is aligned with the first sensor  52  when the second portion  206 ,  306 ,  406  is in the second position  150 . In such embodiments, the first sensor  52  can generate: a first signal when the well  14  is empty; a second signal that is significantly different from the first signal when the biological sterilization indicator  100  is positioned in the well  14  and the second portion  206 ,  306 ,  406  is not in the second position  150  (e.g., is in the first position  148 ); and a third signal that is significantly different from the first signal and the second signal, based on the exposed signal-modulating feature  253 ,  353 ,  453  of the second portion  206 ,  306 ,  406 , when the biological sterilization indicator  100  is positioned in the well  14  and the second portion  206 ,  306 ,  406  of the biological sterilization indicator  100  is in the second position  150 . In some embodiments, as described below with reference to  FIG. 10 , both the first portion  104  and the second portion  106  can include a signal-modulating feature, and in such embodiments, more than one first sensor  52  can be employed. 
     As illustrated by  FIGS. 6-8 , the second portion  106 ,  206 ,  306 ,  406  can include a variety of signal-modulating features (such as signal-modulating features  253 ,  353  and  453 ). That is, the second portion  106 ,  206 ,  306 ,  406  can include any of the signal-modulating features described above with respect to the signal-modulating feature  153  of the first portion  104  of  FIGS. 2-4 , or a combination thereof. 
     The reading apparatus  12  (e.g., the first sensor  52 ) can be configured to sense a variety of signal-modulating features of the biological sterilization indicator  100 . As mentioned above, in some embodiments, the first portion  104  and/or the second portion  106  of the biological sterilization indicator  100  can include a signal-modulating feature that can be detected or sensed by the reading apparatus  12 , for example, to indicate whether the biological sterilization indicator  100  has been activated. However, in some embodiments, another portion of the biological sterilization indicator  100  can include a signal-modulating feature that can generate a uniquely different second signal and third signal. For example, in some embodiments, the container  120 , the insert  130 , and/or another portion of the biological sterilization indicator  100  can include one or more signal-modulating features. Other examples of signal-modulating features that can be employed are described in greater detail below with reference to  FIGS. 9-10 . 
     The signal-modulating feature  153 , and particularly, the flat-to-round transition  152 , that is illustrated in  FIGS. 2-4  is shown by way of example only; however, it should be understood that a variety of signal-modulating features  153  can be employed instead, or in addition to, the signal-modulating feature  153  shown in  FIGS. 2-4 . For example, in some embodiments, the signal-modulating feature  153 , no matter which component(s) of the biological sterilization indicator  100  include, provide or are coupled to the signal-modulating feature  153 , can include, but is not limited to, a protrusion, flange, ledge, recess, or other surface shape change or deflection region or zone, such as the flat-to-round transition  152  of  FIGS. 2-4 , an angled surface, such as the angled surfaces  252  and  352  of  FIGS. 6 and 7 , etc.; a label or color or surface change that provides either a uniquely high or uniquely low signal in reflection, such as the label  452  of  FIG. 8 ; a surface modification, such as that shown in  FIG. 9  and described below; material makeup or additive (e.g., a metal-filled resin) that provides a unique signal; another suitable signal-modulating feature; or a combination thereof. A surface modification can provide deflection, absorbance, diffraction, and/or diffusion of a signal, similar to other signal-modulating features, and can include, but is not limited to, one or more of an etched surface (e.g., formed by a chemical etching process, such as plasma etching, e.g., corona etching, or the like), an abraded surface (e.g., formed by a mechanical (e.g., an abrasion process, sandblasting, etc., or combinations thereof) or optical (e.g., laser) process), a microstructured or microreplicated surface (e.g., formed by a microreplication process), an otherwise textured surface or surface finish (e.g., formed by a molding or manufacturing process), another suitable surface modification, or a combination thereof. In some embodiments, the signal-modulating feature  153  can include an optical property (e.g., color, opacity/translucency, refractive index, etc.) that is different from adjacent regions of the biological sterilization indicator  100 . 
       FIG. 9  illustrates a biological sterilization indicator  500  according to another embodiment of the present disclosure. Elements and features corresponding to elements and features in the illustrated embodiment of  FIGS. 2-4  are provided with the same reference numerals in the  500  series. Reference is made to the description above accompanying  FIGS. 2-4  for a more complete description of the features and elements (and alternatives to such features and elements) of the embodiment illustrated in  FIG. 9 . 
     The biological sterilization indicator  500  includes a housing  502  formed of a first portion  504  and a second portion  506  that are movable relative to one another, for example, to activate (and seal) the biological sterilization indicator  500  after sterilization. The biological sterilization indicator  500  is similar to the biological sterilization indicator  100  of  FIGS. 2-4 , except that the biological sterilization indicator  500  includes a first signal-modulating feature  553  in the form of a flat-to-round transition  552  and a second signal-modulating feature  553 ′ in the form of a surface modification  552 ′. Particularly, the surface modification  552 ′ is in the form of a textured surface, but it should be understood that a variety of other signal-modulating features, such as those mentioned above, can be employed as the second signal-modulating feature  553 ′. By way of example only, the textured surface of the embodiment illustrated in  FIG. 9  can be formed by a texture that is called out by a molding guide, e.g., MT 11010 with a D-2 finish, such that the texture is formed during the manufacturing (e.g., molding) process used to form the housing  502 , and particularly, to form the first portion  504  of the housing  502 . 
     Such a combination or multiplication of signal-modulating features  553 ,  553 ′ on the first portion  504  of the biological sterilization indicator  500  can be used, for example, to ensure that the first sensor  52  receives a signal from the first portion  504  when the second portion  506  is in its first position  548  that is significantly different from the signal received from the second portion  506  when the second portion  506  is in its second position (not shown). In addition, in some embodiments, the surface modification  552 ′ can give a more reliable failure mode when the biological sterilization indicator  100  is incorrectly oriented in the well  14 , for example, because the back of the biological sterilization indicator  100  would not give a similar signal as the smooth second portion  106 . As a result, a first sensor (e.g., the first sensor  52  of the reading apparatus  12  of  FIGS. 1-5 ) would receive a unique intermediate signal from the surface modification  552 ′ (e.g., if the biological sterilization indicator  100  were incorrectly turned around in the well  14 ), and a unique high signal from the smooth second portion  106 . As a result, an incorrectly oriented biological sterilization indicator  100  would not give the same signal to the first sensor as the second portion  106  in its second position, and it would be clear when the biological sterilization indicator  100  was simply incorrectly oriented in the well  14 . 
     The surface modification  552 ′ can also provide a means for minimizing or inhibiting ambient light from reaching a detection chamber, or region to be interrogated, of the biological sterilization indicator  500  (e.g., a second chamber, such as the second chamber  111  of  FIGS. 2-4 ). The surface modification  552 ′ is illustrated and described above by way of example only as being a textured surface. However, other surface modifications that include one or more of any of the above signal-modulating features can also employed to inhibit ambient light from reaching certain portions of the biological sterilization indicator  500 . For example, the surface modification could additionally or alternatively include a color (e.g., a dye), a reflective surface, could be opaque, could include other suitable optical properties for inhibiting ambient light from entering the biological sterilization indicator  500 , or combinations thereof. 
     In some embodiments, ambient light can affect assaying or detection techniques, such as fluorescence detection, that are employed to assay for growth or viability of a source of biological activity. By modifying at least a portion of a surface (e.g., an outer surface or an inner surface) of the housing  502 , such ambient light can be scattered and inhibited from being transmitted along the biological sterilization indicator  500  to a region that may affect assay results. The configuration and location of the surface modification  552 ′ is shown by way of example only, and could be employed, such that when the second portion  506  of the housing  502  is in a second or closed position, any ambient light around the biological sterilization indicator  500  would encounter the surface modification  552 ′ on the first portion  504  of the housing  502 , and be sufficiently scattered by the surface modification  552 ′, such that the ambient light is inhibited from entering the biological sterilization indicator  500  and reaching a lower portion (e.g., the lower portion  114  of  FIGS. 2-4 ) or detection chamber (e.g., the second chamber  111  of  FIGS. 2-4 ) of the biological sterilization indicator  500 . In some embodiments, such as the embodiment shown in  FIG. 9 , the surface modification  552 ′ can be positioned on the first portion  504 . In such embodiments, any ambient light entering the biological sterilization indicator  500 , through any path, would be scattered by the surface modification  552 ′; for example, light passing through the second portion  506  (e.g., if the second portion  506  is not completely opaque); light passing through apertures in the second portion  506 , such as apertures  107  of  FIG. 2  (e.g., through a barrier or filter positioned over the apertures); light passing just below the second portion  206  (e.g., between the biological sterilization indicator  500  and a well of a reading apparatus that the biological sterilization indicator  500  is positioned in during detection); or combinations thereof. 
     Other similar surface modification means can be employed for inhibiting ambient light from reaching certain portions of the biological sterilization indicator  500  where such ambient light may interfere with assaying or detection processes. A method for testing whether ambient light is reaching certain portions of the biological sterilization indicator  500  can include turning off any excitation sources, such as the excitation source  72  of  FIGS. 3-4  (e.g., LEDs) of a reading apparatus, and using a detector, such as the detector  74  of  FIGS. 3-4  to see if any ambient light is being detected by the detector (e.g., if the detector registers a non-zero lighting condition) at a frequency (e.g., at 450 nm) that may correspond to and interfere with the detection process. 
       FIG. 10  illustrates a biological sterilization indicator system  10 ′ according to another embodiment of the present disclosure. The biological sterilization indicator system  10 ′ includes a reading apparatus  12 ′ and a biological sterilization indicator  600 . The reading apparatus  12 ′ is similar to the reading apparatus  12  of  FIGS. 1-4 , and therefore, the reading apparatus  12 ′ is provided with substantially the same reference numerals as the reading apparatus  12 , with additional or different elements referenced with a “prime” symbol after the number. Elements and features of the biological sterilization indicator  600  corresponding to elements and features in the illustrated embodiment of  FIGS. 1-4  are provided with the same reference numerals in the  600  series. Reference is made to the description above accompanying  FIGS. 1-4  for a more complete description of the features and elements (and alternatives to such features and elements) of the embodiment illustrated in  FIG. 10 . 
     The biological sterilization indicator  600  includes a housing  602  formed of a first portion  604  and a second portion  606  that are movable relative to one another (e.g., to activate (and seal) the biological sterilization indicator  600  after sterilization) between a first position  648  (shown in phantom lines) and a second position  650  (shown in solid lines). As shown in  FIG. 10 , the second portion  606  includes a signal-modulating feature  653  in the form of an inwardly-extending surface  652  adjacent a bottom edge of the second portion  606  (similar to the second portion  206  of  FIG. 6 ). In addition, the first portion  604  includes a signal-modulating feature  653 ′ in the form of a flat-to-round transition  652 ′, similar to that of the biological sterilization indicator  100  of  FIGS. 2-4  described above. 
     The biological sterilization indicator system  10 ′ of  FIG. 10  can function similarly as the biological sterilization indicator system  10  of  FIGS. 1-5 , and can include similar components, except that the reading apparatus  12 ′ includes a third sensor (or additional “first” sensor)  52 ′. As shown in  FIG. 10 , in some embodiments, the first sensor  52  can be positioned adjacent the signal-modulating feature  653  of the second portion  606  when the second portion  606  is in the second position  650 , such that when the second portion  606  is in the first position  648 , the smooth outer wall (i.e., not in the region of the flat-to-round transition  652 ′) of the first portion  604  will present a uniquely high signal to the first sensor  52 , but when the second portion  606  is in the second position  650 , the second portion  606  will obscure such a uniquely high signal and will present a unique signal (e.g., a uniquely intermediate signal) to the first sensor  52 . The third sensor  52 ′, on the other hand, can be positioned to be adjacent the signal-modulating feature  653 ′ of the first portion  604  when the biological sterilization indicator  600  is fully seated in the well  14  of the reading apparatus  12 ′, such that the unique modified signal from the signal-modulating feature  653 ′ can be detected by the third sensor  52 ′ when the second portion  606  is in the first position  648  or the second position  650 . 
     In such embodiments, the first sensor  52  can generate (and the controller  51  can receive): a first signal (e.g., relatively low) when the well  14  is empty; a second signal, based on the smooth outer wall/surface of the exposed first portion  604 , that is significantly different from the first signal, when the biological sterilization indicator  600  is positioned in the well  14  and the second portion  606  is not in the second position  650  (e.g., is in the first position  648 ); and a third signal, based on the signal-modulating feature  653  of the second portion  206 , that is significantly different from the first signal and the second signal, when the biological sterilization indicator  600  is positioned in the well  14  and the second portion  606  is in the second position  650 . 
     In addition, the third sensor  52 ′ can generate (and the controller  51  can receive) a first signal (e.g., relatively low) when the well  14  is empty; and a second signal that is significantly different from the first signal, based on the signal-modulating feature  653 ′ of the first portion  604 . In addition, the third sensor  52 ′ will indicate when the biological sterilization indicator  600  is incorrectly positioned in the well  14 , because in some embodiments, the third sensor  52 ′ can generate a third signal that is significantly different from the first signal and the second signal when the biological sterilization indicator  600  is turned around (i.e., positioned incorrectly) in the well  14 . For example, if the biological sterilization indicator  600  were incorrectly oriented in the well  14 , the third sensor  52 ′ would no longer line up with the signal-modulating feature  653 ′ of the first portion  604  to confirm that the biological sterilization indicator  600  is fully seated in the well  14 , but rather the third sensor  52 ′ would line up with a different portion of the biological sterilization indicator  600  (e.g., the smooth outer wall opposite the signal-modulating feature  653 ′) and produce a relatively high signal, compared to the unique signal of the signal-modulating feature  653 ′. As a result, when the third sensor  52 ′ sends the second signal and the first sensor  52  sends the third signal to a controller  51 , the controller  51  can begin to initiate a spore growth and/or detection process, or the assay result will be output to the display  16  without an error code. 
     The first sensor  52  and the third sensor  52 ′ can form a portion of a dedicated detection system  55 ′ that is dedicated to the well  14  illustrated in  FIG. 10 , and which can further include the second sensor  54 . As described above, the second sensor  54  can include the excitation source  72  and the detector  74 , and can be used to confirm that the biological sterilization indicator  600  is fully seated in the well  14  (e.g., to reliably confirm activation of the biological sterilization indicator  600 ), and/or to perform the detection or assaying process by interrogating the biological sterilization indicator  600  for spore growth. 
     While the biological sterilization indicator systems  10  and  10 ′, the biological sterilization indicators  100 ,  500 , and  600 , and the second portions  106 ,  206 ,  306 ,  406 ,  506 , and  606  are described above as individual embodiments, it should be understood that a biological sterilization indicator system of the present disclosure can include any combination of the various features and elements described above and shown in  FIGS. 1-10  that accomplishes the desired biological sterilization indicator system functions. 
     Furthermore, even though only one first sensor  52  is shown and described with respect to the reading apparatus  12  and the biological sterilization indicator system  10 , and two first sensors  52 ,  52 ′ are shown and described with respect to the reading apparatus  12 ′ and the biological sterilization indicator system  10 ′, it should be understood from the present disclosure that as many such first sensors  52  as necessary can be employed to detect a variety of signal-modulating features on various components of a biological sterilization indicator  100 ,  600  in order to confirm that the second portion  106 ,  606  of the biological sterilization indicator  100 ,  600  has moved a sufficient amount, and to confirm activation of the biological sterilization indicator  100 ,  600 . 
     Embodiments 
     Embodiment 1 is a biological sterilization indicator system, the system comprising:
         a biological sterilization indicator comprising:
           a housing including
               a first portion, and   a second portion adapted to be coupled to the first portion, the second portion being movable with respect to the first portion, when coupled to the first portion, between a first position and a second position; and   
               a container containing a liquid and being dimensioned to be positioned in the housing, at least a portion of the container being frangible, the container positioned in at least the first portion of the housing, the container having a first state in which the container is intact when the second portion of the housing is in the first position, and a second state in which the container is fractured when the second portion of the housing is in the second position; and   
           a reading apparatus comprising a well, the well dimensioned to receive at least a portion of the biological sterilization indicator, the reading apparatus adapted to generate-at least one of:
           a first signal indicative of the well being empty,   a second signal indicative of the biological sterilization indicator being positioned in the well with the second portion of the housing in the first position, and   a third signal indicative of the biological sterilization indicator being positioned in the well with the second portion of the housing in the second position.   
               

     Embodiment 2 is a method for detecting an activation status of a biological sterilization indicator, the method comprising:
         providing a biological sterilization indicator comprising:
           a housing including
               a first portion, and   a second portion adapted to be coupled to the first portion, the second portion being movable with respect to the first portion between a first position and a second position; and   
               a container containing a liquid, at least a portion of the container being frangible, the container positioned in at least the first portion of the housing, the container having a first state in which the container is intact when the second portion of the housing is in the first position, and a second state in which the container is fractured when the second portion of the housing is in the second position;   
           providing a reading apparatus comprising a well dimensioned to receive at least a portion of the biological sterilization indicator;   generating a first signal when the well is empty;   positioning the biological sterilization indicator in the well of the reading apparatus; and   generating at least one of the following signals:
           a second signal when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the first position, and   a third signal when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the second position.   
               

     Embodiment 3 is a biological sterilization indicator system, the system comprising:
         a biological sterilization indicator comprising:
           a housing including
               a first portion, and   a second portion adapted to be coupled to the first portion, the second portion being movable with respect to the first portion, when coupled to the first portion, between a first position and a second position; and   
               a container containing a liquid and being dimensioned to be positioned in the housing, at least a portion of the container being frangible, the container positioned in at least the first portion of the housing, the container having a first state in which the container is intact when the second portion of the housing is in the first position, and a second state in which the container is fractured when the second portion of the housing is in the second position; and   
           a reading apparatus comprising a well, the well dimensioned to receive at least a portion of the biological sterilization indicator, the reading apparatus configured to detect at least one of the following conditions:
           when the well is empty,   when the biological sterilization indicator is positioned in the well with the second portion of the housing in the first position, and   when the biological sterilization indicator is positioned in the well with the second portion of the housing in the second position.   
               

     Embodiment 4 is a method for detecting an activation status of a biological sterilization indicator, the method comprising:
         providing a biological sterilization indicator comprising:
           a housing including
               a first portion, and   a second portion adapted to be coupled to the first portion, the second portion being movable with respect to the first portion between a first position and a second position; and   
               a container containing a liquid, at least a portion of the container being frangible, the container positioned in at least the first portion of the housing, the container having a first state in which the container is intact when the second portion of the housing is in the first position, and a second state in which the container is fractured when the second portion of the housing is in the second position;   
           providing a reading apparatus comprising a well dimensioned to receive at least a portion of the biological sterilization indicator; and   detecting at least one of the following conditions:
           when the well is empty;   when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the first position, and   when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the second position.   
               

     Embodiment 5 is the system or method of any above embodiment, wherein the first portion of the housing includes an open end and a closed end, and wherein the second portion of the housing is adapted to be coupled to the open end of the first portion of the housing. 
     Embodiment 6 is the system or method of any above embodiment, wherein the second position is located closer to the closed end of the first portion of the housing than the first position. 
     Embodiment 7 is the system or method of any above embodiment, wherein the biological sterilization indicator is open to ambience when the second portion of the housing is in the first position, and wherein the biological sterilization indicator is sealed from ambience when the second portion of the housing is in the second position. 
     Embodiment 8 is the system or method of any above embodiment, wherein the housing includes a longitudinal direction, and wherein the second portion of the housing is movable in the longitudinal direction with respect to the first portion between the first position and the second position. 
     Embodiment 9 is the system or method of any above embodiment, wherein the container is in the first state when the second portion of the housing is in the first position, and wherein the container is in the second state when the second portion of the housing is in the second position. 
     Embodiment 10 is the system or method of any above embodiment, wherein the reading apparatus is configured to incubate the biological sterilization indicator. 
     Embodiment 11 is the system or method of any above embodiment, wherein the second portion of the housing is movable with respect to the first portion of the housing when the biological sterilization indicator is positioned in the well of the reading apparatus, and when the biological sterilization indicator is located outside of the well of the reading apparatus. 
     Embodiment 12 is the system or method of any above embodiment, wherein the biological sterilization indicator and the well are keyed with respect to one another, such that the biological sterilization indicator is positioned fully within the well in only one orientation. 
     Embodiment 13 is the system or method of any above embodiment, wherein the housing includes a longitudinal direction, and wherein the container is movable in the longitudinal direction of the housing in response to movement of the second portion of the housing between the first position and the second position. 
     Embodiment 14 is the system or method of any above embodiment, wherein the second portion of the housing is in the first position during sterilization, and wherein the second portion of the housing is in the second position after activation. 
     Embodiment 15 is the system or method of any of embodiments 3-14, wherein the reading apparatus is configured to generate at least one of:
         a first signal when the well is empty;   a second signal when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the first position; and   a third signal when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the second position.       

     Embodiment 16 is the system of any of embodiments 3-15, wherein the reading apparatus is configured to generate at least one signal, each signal being indicative of one of the detected conditions. 
     Embodiment 17 is the method of any of embodiments 4-16, further comprising positioning the biological sterilization indicator in the well of the reading apparatus. 
     Embodiment 18 is the method of any of embodiments 4-17, further comprising:
         generating a first signal when the well is empty;   positioning the biological sterilization indicator in the well of the reading apparatus; and   generating at least one of:
           a first signal indicative of when the biological sterilization indicator is positioned in the well with the second portion of the housing in the first position, and   a second signal indicative of when the biological sterilization indicator is positioned in the well with the second portion of the housing in the second position.   
               

     Embodiment 19 is the system of embodiment 15 or the method of embodiment 18, wherein the reading apparatus is configured to generate an error code when the first signal or the second signal is generated. 
     Embodiment 20 is the system or method of any above embodiment, wherein the reading apparatus includes a first sensor positioned adjacent a signal-modulating feature of at least one of the first portion of the housing and the second portion of the housing. 
     Embodiment 21 is the system or method of any above embodiment, wherein the reading apparatus includes a first sensor configured to sense a signal-modulating feature of the biological sterilization indicator. 
     Embodiment 22 is the system or method of embodiment 21, wherein at least one of the first portion of the housing and the second portion of the housing of the biological sterilization indicator includes the signal-modulating feature. 
     Embodiment 23 is the system of any of embodiments 15 and 19 or the method of any of embodiments 18-19, wherein the first portion of the housing of the biological sterilization indicator includes a signal-modulating feature, and wherein the second signal is at least partially determined by the signal-modulating feature of the first portion of the housing. 
     Embodiment 24 is the system of any of embodiments 15, 19 and 23 or the method of any of embodiments 18-19 and 23 wherein the second portion of the housing of the biological sterilization indicator includes a signal-modulating feature, and wherein the third signal is at least partially determined by the signal-modulating feature of the second portion of the housing. 
     Embodiment 25 is the system or method of any above embodiment, wherein the first portion of the housing of the biological sterilization indicator includes a signal-modulating feature that is exposed to the reading apparatus when the second portion of the housing is in the first position and is not exposed to the reading apparatus when the second portion of the housing is in the second position. 
     Embodiment 26 is the system or method of any above embodiment, wherein the reading apparatus includes a first sensor configured to generate a first signal when the well is empty, and wherein the first portion of the housing of the biological sterilization indicator includes a signal-modulating feature that is exposed to the first sensor when the second portion of the housing is in the first position and obscured by the second portion when the second portion is in the second position, such that the first sensor generates:
         a second signal, based on the signal-modulating feature, when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the first position, that is different from the first signal, and   a third signal when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the second position, that is different from the first signal and the second signal.       

     Embodiment 27 is the system or method of embodiment 25 or 26, wherein the signal-modulating feature on the first portion of the housing of the biological sterilization indicator includes a flat-to-round transition area on an outer surface of the first portion of the housing. 
     Embodiment 28 is the system or method of any of embodiments 25-27, wherein the signal-modulating feature on the first portion of the housing of the biological sterilization indicator includes at least one of a protrusion and a recess. 
     Embodiment 29 is the system or method of any of embodiments 25-28, wherein the signal-modulating feature on the first portion of the housing of the biological sterilization indicator includes a label coupled to an outer surface of the first portion of the housing. 
     Embodiment 30 is the system or method of any of embodiments 25-29, wherein the signal-modulating feature on the first portion of the housing of the biological sterilization indicator includes a surface modification on an outer surface of the first portion of the housing. 
     Embodiment 31 is the system or method of any of embodiments 25-30, wherein the signal-modulating feature on the first portion of the housing is a first signal-modulating feature, and wherein the second portion of the housing includes a second signal-modulating feature that is exposed when the second portion of the housing is in the second position. 
     Embodiment 32 is the system or method of embodiment 29, wherein the first signal-modulating feature is different from the second signal-modulating feature. 
     Embodiment 33 is the system or method of any above embodiment, wherein the second portion of the housing of the biological sterilization indicator includes a signal-modulating feature that is exposed to the reading apparatus when the second portion of the housing is in the second position and is not exposed to the reading apparatus when the second portion of the housing is in the first position. 
     Embodiment 34 is the system or method of any above embodiment, wherein the reading apparatus includes a first sensor configured to generate a first signal when the well is empty, and wherein the second portion of the housing includes a signal-modulating feature that is exposed when the second portion of the housing is in the second position, such that the first sensor generates:
         a second signal when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the first position, that is different from the first signal, and   a third signal, based on the exposed signal-modulating feature, when the biological sterilization indicator is positioned in the well and the second portion of the housing is in the second position, that is different from the first signal and the second signal.       

     Embodiment 35 is the system or method of embodiment 33 or 34, wherein the signal-modulating feature on the second portion of the housing of the biological sterilization indicator includes at least one of a protrusion and a recess. 
     Embodiment 36 is the system or method of any of embodiments 33-35, wherein the signal-modulating feature on the second portion of the housing of the biological sterilization indicator includes a label. 
     Embodiment 37 is the system or method of any of embodiments 33-36, wherein the signal-modulating feature on the second portion of the housing of the biological sterilization indicator includes an optical property. 
     Embodiment 38 is the system or method of any of embodiments 33-37, wherein the signal-modulating feature on the second portion of the housing of the biological sterilization indicator includes a surface modification. 
     Embodiment 39 is the system or method of any above embodiment, wherein the reading apparatus includes a first sensor positioned adjacent the well, the first sensor configured to generate at least one of the first signal, the second signal, and the third signal. 
     Embodiment 40 is the system or method of embodiment 39, wherein the reading apparatus includes a second sensor configured to generate at least one signal indicative of whether the biological sterilization indicator is fully seated in the well. 
     Embodiment 41 is the system or method of any above embodiment, wherein the reading apparatus includes: 
     a first sensor positioned adjacent a first region of the well, the first sensor configured to generate at least one of:
         a first signal indicative of the first region of the well being empty,   a second signal indicative of the biological sterilization indicator being positioned in the first region of the well with the second portion of the housing in the first position, and   a third signal indicative of the biological sterilization indicator being positioned in the first region of the well with the second portion of the housing in the second position; and       

     a second sensor positioned adjacent a second region of the well, the second sensor configured to generate at least one of:
         a fourth signal indicative of the second region of the well being empty, and   a fifth signal indicative of the biological sterilization indicator being positioned in the second region of the well.       

     Embodiment 42 is the system or method of embodiment 41, wherein the reading apparatus is configured to generate an error code when the second sensor generates the fourth signal. 
     Embodiment 43 is the system or method of embodiment 41 or 42, wherein the reading apparatus is configured to generate an error code when the first sensor generates the first signal or the second signal, and the second sensor generates the fifth signal. 
     Embodiment 44 is the system or method of any of embodiments 41-43, wherein the first region of the well is an upper region, and wherein the second region of the well is a lower region. 
     Embodiment 45 is the system or method of any of embodiments 41-44, wherein the first region of the well is a first longitudinal region of the well, and wherein the second region of the well is a second longitudinal region of the well, spaced a longitudinal distance from the first region. 
     Embodiment 46 is the system or method of any of embodiment 20, 21 and 26-45, wherein the first sensor includes a photointerrupter. 
     Embodiment 47 is the system or method of any of embodiments 40-46, wherein the second sensor comprises a fluorescence detection system including an excitation light source and a detector. 
     Embodiment 48 is the system or method of any of embodiments 40-46, wherein the second sensor includes a photointerrupter. 
     Embodiment 49 is the method of any of embodiments 2, 4-14 and 17-48, further comprising moving the second portion of the housing from the first position to the second position to activate the biological sterilization indicator. 
     Embodiment 50 is the method of embodiment 49, wherein moving the second portion of the housing from the first position to the second position occurs before positioning the biological sterilization indicator in the well, such that first signal is generated before the biological sterilization indicator is positioned in the well, and when the biological sterilization indicator is positioned in the well, the third signal is generated and the second signal is not generated. 
     Embodiment 51 is the method of embodiment 49, wherein moving the second portion of the housing from the first position to the second position occurs after positioning the biological sterilization indicator in the well, such that the first signal is generated before the biological sterilization indicator is positioned in the well, and when the biological sterilization indicator is positioned in the well, the second signal is generated, and when the second portion of the housing is moved to the second position, the third signal is generated. 
     Embodiment 52 is the method of any of embodiments 18-19, 23-24, and 39-40 wherein generating the first signal, the second signal and the third signal is performed by a first sensor of the reading apparatus positioned adjacent a first region of the well, wherein the reading apparatus further includes a second sensor positioned adjacent a second region of the well, and further comprising generating at least one of the following signals with the second sensor:
         a fourth signal indicative of the second region of the well being empty, and   a fifth signal indicative of the biological sterilization indicator being present in the second region of the well.       

     Embodiment 53 is the system of any of embodiments 15, 19, 23-24 and 39-40, wherein the reading apparatus is configured to generate the first signal and the third signal only. 
     Embodiment 54 is the system of any of embodiments 15, 19, 23-24 and 39-40, wherein the reading apparatus is configured to generate at least two of the first signal, the second signal, and the third signal. 
     Embodiment 55 is the system or method of any of the above embodiments, wherein at least a portion of the housing of the biological sterilization indicator includes a surface modification. 
     Embodiment 56 is a biological sterilization indicator comprising:
         a housing;   a container containing a liquid and being dimensioned to be positioned in the housing, at least a portion of the container being frangible, the container having a first state in which the container is intact and the liquid is not in fluid communication with an interior of the housing and a second state in which the container is fractured and the liquid is in fluid communication with the interior of the housing;   a first chamber in the housing in which the container is positioned when the container is in the first state; and   a second chamber in the housing in which the container and the liquid are not positioned when the container is in the first state, the second chamber comprising a source of biological activity that is not in fluid communication with the liquid when the container is in the first state and that is in fluid communication with the liquid when the container is in the second state; and   wherein at least a portion of the housing includes a surface modification positioned to inhibit ambient light from reaching the second chamber of the biological sterilization indicator.       

     Embodiment 57 is the biological sterilization indicator of embodiment 56, wherein the surface modification includes a textured surface. 
     Embodiment 58 is the biological sterilization indicator of embodiment 56 or 57, wherein the housing of the biological sterilization indicator includes:
         a first portion, and   a second portion adapted to be coupled to the first portion, the second portion being movable with respect to the first portion, when coupled to the first portion, between a first position and a second position; and   wherein the first portion of the housing includes the surface modification.       

     Embodiment 59 is the biological sterilization indicator of embodiment 58, wherein the surface modification is located on an upper portion of the first portion of the housing. 
     Embodiment 60 is the biological sterilization indicator of any of embodiments 56-59, wherein the surface modification is configured to scatter ambient light. 
     Embodiment 61 is the biological sterilization indicator of any of embodiments 56-60, wherein the surface modification is positioned to inhibit ambient light from reaching the second chamber of the biological sterilization indicator when the biological sterilization indicator is positioned in a well of a reading apparatus. 
     The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present disclosure. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present disclosure. Various features and aspects of the present disclosure are set forth in the following claims.