Patent Description:
Traditional automated phenotypic ID tests, such as the Vitek®, Phoenix™ and Microscan® systems, or manual phenotypic tests such as API require that microorganisms be in an appropriate growth phase and free of interfering media and blood products in order to provide robust results. These systems use colonies grown from the positive broth for <NUM>-<NUM> hours on plated media. However, in an effort to obtain faster results. some laboratories have reported using these systems with microorganisms isolated from clinical samples. Faster and more broadly specific tests are urgently needed in order to provide the physician with clinically relevant results.

Identifying microorganisms cultured in liquid media is particularly difficult because of the lower concentration of microorganisms in the sample container and because the liquid media may interfere with analytical methods such as mass spectrometry.

Mass spectrometric methods have the potential to allow for identification of microorganisms very quickly, but may encounter interference from the many compounds present in liquid culture media and in clinical samples such as sputum, sterile body fluids, or combinations thereof.

Other methods for characterization and/or identification of microorganisms have been described, including:.

<CIT>, which discloses a method for the chemotaxonomic classification of bacteria with genus, species and strain specific biomarkers generated by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis of either cellular protein extracts or whole cells.

<CIT>, which discloses a method for the inactivation and extraction of acid-fast bacteria, such as Mycobacterium and Nocardia, from solid and liquid media. The '<NUM> Patent, however, does not recognize the difficulty associated with the protein extraction of acid-fast bacteria when grown in liquid media. In particular, the '<NUM> Patent does not recognize the difficulty in securing a sufficient amount of biomass of microorganisms from liquid media for identification using mass spectrometry. Further, the '<NUM> Patent does not recognize the difficulty in removing the inactivating solution, which interferes with identification using mass spectrometry. The '<NUM> Patent does not recognize the unexpected benefits of collection and retention of sufficient biomass of the acid fast bacteria for the inactivation and extraction in a tube having a specific size and/or shape. Finally, the '<NUM> Patent does not address the difficulty of separating the pellet from liquid media to avoid interference for identification using mass spectrometry.

<NPL>) describe the inactivation of acid-fast bacteria from plate cultures before mass spectrometry measurements.

<NPL>) describe an inactivation method of mycobacteria comprising multiple work intensive steps.

Thus, there remains a need in the art for efficient and rapid protocols for the inactivation and/or extraction of microorganisms from liquid media for subsequent analysis, characterization and/or identification by mass spectrometry. In particular. inactivation, or cell death, is often necessary for subsequent handling of acid-fast bacteria, such as Mycobacterium and Nocardia, outside a Biosafety Level-<NUM> (BSL-<NUM>/P3) environment.

In one aspect, the present invention is directed to a method for inactivation and extraction of acid-fast bacteria (e.g., Mycobacterium or Nocardia species) in a test sample, the method comprising the following sequential steps: (a) culturing a test sample containing acid-fast bacteria in a liquid culture and continuing to culture the test sample in the liquid culture for at least <NUM> hours after the test sample has tested positive for growth of the acid-fast bacteria and until a minimum concentration of <NUM>. 0x10<NUM> CFU/ml is present in the test sample culture; (b) transferring the test sample from the positive liquid culture to a first tube, wherein the first tube comprises a body having a volume of <NUM>, a first end to the body having an opening, and a second end to the body having a frustoconical portion ending in a concave tip; (c) centrifuging the first tube to pellet the acid-fast bacteria in the concave tip and subsequently decanting at least <NUM>% of a first supernatant while retaining the pellet of acid-fast bacteria in the concave tip; (d) resuspending the acid-fast bacteria pellet in alcohol, optionally ethanol, to generate a first suspension; (e) transferring the suspension from the first tube to a second tube containing beads to form a second suspension; (f) agitating the second tube to break up clumps and disrupt acid-fast bacteria cells in the second suspension; and (g) incubating the second suspension for at least <NUM> minutes to inactivate the acid-fast bacteria in the test sample to form an inactivated second suspension; optionally wherein said acid-fast bacteria is Mycobacterium or Nocardia.

In one embodiment, the acid-fast bacteria (e.g., Mycobacterium or Nocardia) pellet can be resuspended in step (d) in from about <NUM>% to about <NUM>% ethanol, for example, the pellet may be resuspended in about <NUM>% ethanol. The method may comprise bead beating and/or vortexing the container in step (f) for about <NUM> minute to about <NUM> minutes. In one embodiment, the beads are <NUM> glass beads. In one embodiment, the subsequent incubation step (g) comprises an incubation for at least about <NUM> minutes. In another embodiment, the incubation in step (g) is at room temperature.

In another embodiment, the method may further comprise the following additional sequential steps as part of protein extraction: (h) transferring the suspension to a third tube and centrifuging the third tube to pellet the inactivated acid-fast bacteria and subsequently removing a second supernatant; and (i) resuspending the inactivated acid-fast bacteria pellet to generate a solution comprising the inactivated acid-fast bacteria. In some embodiments. the supematant from step (i) can be applied directly, or as a water suspension, to a mass spectrometry slide or plate.

The pellet in step (h) may be resuspended using from about <NUM>% to about <NUM>% formic acid, for example, the pellet may be resuspended using <NUM>% formic acid, in step (i). After resuspending the pellet, acetonitrile may be added to obtain a final concentration of acetonitrile of from about <NUM>% to about <NUM>%, for example, to obtain a final concentration of about <NUM>%. In one embodiment. the pellet may be resuspended in <NUM>µL of formic acid in step (h) and <NUM>µL of acetonitrile can be added to the resuspended pellet in step (h). In some embodiments, the suspension may be centrifuged to pellet cellular debris as shown in step (j).

In accordance with this embodiment, the method may further comprises the following additional sequential steps: (k) transferring an aliquot of the supernatant from step (j) to a mass spectrometry target slide and adding a matrix solution, and (l) identifying protein profiles of the inactivated acid-fast bacteria on the mass spectrometry slide by mass spectrometry to acquire one or more mass spectra of the acid-fast bacteria and characterizing and/or identifying said acid-fast bacteria in the test sample by comparison of the measured mass spectrum with one or more reference mass spectra. Optionally, step <NUM> (k) comprises transferring an aliquot (e.g., <NUM>µL) of the test sample obtained from step (j) to a mass spectrometry slide or plate, allowing the aliquot to dry and subsequently adding a matrix. Any known matrix may be used. for example. the matrix may be alpha-cyano-<NUM>-hydroxycinnamic acid (CHCA). In accordance with the present invention, the acid-fast bacteria can be identified to the family, genus, species, strain level and/or group/complex using mass spectrometry, for example, MALDI-TOF mass spectrometry.

The method and kit of this disclosure will be described in conjunction with the appended drawings, in which:.

The present assignee's VITEK® MS system (bioMérieux, Inc. Louis, MO) provides a platform for bacterial identification using a Matrix Assisted Laser Desorption Ionization - Time of Flight (MALDI-TOF) Mass Spectrometer to analyze the protein profile of a sample and match it to a database of known organism profiles. Samples are deposited onto a target slide, covered with a matrix (e.g., CHCA matrix (α-cyano-<NUM>-hydroxy-cinamic acid matrix)), and then processed through the Mass Spectrometer.

Most common clinically-relevant microorganism can be analyzed by depositing cells directly onto the VITEK® MS target slide. The preparation of acid-fast bacteria (e.g., Mycobacterium or Nocardia) samples for analysis differs from the standard procedure in that an inactivation step is necessary in order to make the samples safe for handling outside of a Biosafety Level-<NUM> (BSL-<NUM>/P3) environment. Further, analyzing samples from liquid media results in challenges in securing adequate amounts of biomass as well as clearing inactivating solution that will interfere with identification.

The present applicants have found that incubation in alcohol in conjunction with mechanical disruption provides an effective and rapid method for the inactivation of acid-fast bacteria. Alcohol exposure was shown to be effective when using a process involving an agitation or mechanical disruption step followed by subsequent inactivation step by incubating the disrupted sample in alcohol at room temperature for at least <NUM> minutes, or at least <NUM> minutes. In some embodiments, the alcohol is ethanol. In one embodiment, mechanical disruption is performed using a vortex or a Bead Beater (BioSpec. Bartlesville, OK), a homogenizer that disrupts cells by agitating a sealed micro centrifuge tube containing sample, extraction solution, and beads (e.g., tiny glass beads). Typically, the beads can be any known beads that can operate to disrupt cells in a container or microcentrifuge tube. For example, the beads can be glass, ceramic, zirconia, silicon, metal, steel, tungsten carbide, gamet, sand, or sapphire beads. In one embodiment, the bead can be from about <NUM> to about <NUM> in size, for example, about <NUM> in size.

Additional processing steps can then be used to assist in extracting the cellular proteins from the inactivated cells in order to yield clear and consistent spectra. For example, a treatment step in formic acid followed by exposure to acetonitrile can be used to extract and dissolve proteins for subsequent analysis (e.g., by mass spectrometry).

The present invention provides methods for the inactivation, extraction. characterization, and/or identification of an unknown acid-fast bacterium in a test sample from liquid media. The present invention is also directed to a method for the rapid characterization and/or identification of acid-fast bacteria (e.g., Mycobacterium or Nocardia) in a test sample from liquid media using mass spectrometry. The rapid methods allow for characterization and/or identification of acid-fast bacteria more quickly than prior techniques, resulting in faster diagnoses and characterization/identification of test samples. The steps involved in the methods of the invention, from obtaining a sample to characterization/identification of acid-fast bacteria. can be carried out in a very short time frame to obtain clinically relevant actionable information. In certain embodiments, the methods of the invention can be carried out in less than about <NUM> minutes, e.g., in less than about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> minutes. The rapidity of the methods of the invention represents an improvement over prior methods.

In one embodiment of the invention. samples are obtained from a subject (e.g., a patient) having or suspected of having an acid-fast bacterial infection. As used herein, the term "acid-fast bacteria" is intended to encompass any acid-fast bacteria including, but not limited to, Mycobacterium and Actinomyces (including Nocardia, Rhodococcus. Gordonia, Tsukamurella and Dietzia).

As used herein, the term "mycobacteria" or "Mycobacterium" is intended to encompass any known mycobacteria. including, but not limited to, rapid and slow-growing bacteria such as Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium microti, Mycobacterium africanum, Mycobacterium canetti, Mycobacterium avium. Mycobacterium intracellulare, Mycobacterium scrofulaceum, Mycobacterium kansasii, Mycobacterium malmoense. Mycobacterium xenopi, Mycobacterium marinum, Mycobacterium simiae. Mycobacterium terrae, Mycobacterium ulcerans, Mycobacterium abscessus, Mycobacterium fortuitum, Mycobacterium chelonae, Mycobacterium smegmatis, Mycobacterium alvei, Mycobacterium farcinogenes, Mycobacterium fortuitum ssp fortuitum, Mycobacteirum houstonense, Mycobacterium peregrinum. Mycobacterium porcinum, Mycobacterium senegalense. Mycobacterium genavense, Mycobacterium haemophilum, Mycobacterium immunogenum, Mycobacterium lentiflavum, Mycobacterium mucogenicum, Mycobacterium szulgai, Mycobacterium tuberculosis complex and Mycobacterium gordotae. In some embodiments, the rapid growers such as M. abscessus, M. chelonae, and M. smegmatis, can be identified in a short period of time, which assists in diagnosis and treatment. Unexpectedly, slow growing Mycobacterium species can also be inactivated and extracted quickly, and then identified in a short period of time, as shown in <FIG>.

As used herein, the term "Nocardia" is intended to encompass any known Nocardia, including, but not limited to, Nocardia aerocolonigenes, Nocardia africana, Nocardia argentinensis, Nocardia asteroids, Nocardia blackwellii, Nocardia brasiliensis. Nocardia brevicatena, Nocardia camea, Nocardia caviae, Nocardia cerradoensis, Nocardia corallina, Nocardia cyriacigeorgica, Nocardia dassonvillei, Nocardia elegans. Nocardia farcinica, Nocardia nrgiitansis, Nocardia nova, Nocardia opaca, Nocardia otitidis-cavarium, Nocardia paucivorans, Nocardia pseudobrasiliensis, Nocardia rubra, Nocardia seriolae, Nocardia transvelencesis, Nocardia uniformis, Nocardia vaccinii, and Nocardia veterana.

As used herein, "characterization" encompasses the broad categorization or classification of biological particles and/or the actual identification of a family, genus, species, and/or strain level or groups/complex of an acid-fast bacteria. Classification may comprise determination of phenotypic and/or morphologic characteristics for the acid-fast bacteria. For example, characterization of the bacteria may be accomplished based on observable differences. such as composition, shape, size, pigmentation, clustering, and/or metabolism.

As used herein "identification" means determining to which family, genus, species, strain or group/complex of a previously unknown acid-fast bacteria (e.g., Mycobacterium or Nocardia) belongs to. For example, identifying a previously unknown acid-fast bacteria to the family, genus, species, strain level, and/or groups/complex.

The present invention is directed to a method for inactivation and extraction of acid-fast bacteria in a test sample, the method comprising the following sequential steps: (a) culturing a test sample containing acid-fast bacteria in a liquid culture and continuing to culture the test sample in the liquid culture for at least <NUM> hours after the test sample has tested positive for growth of the acid-fast bacteria and until a minimum concentration of <NUM>. 0x10<NUM> CFU/ml is present in the test sample culture; (b) transferring the test sample from the positive liquid culture to a first tube, wherein the first tube comprises a body having a volume of <NUM>, a first end to the body having an opening, and a second end to the body having a frustoconical portion ending in a concave tip; (c) centrifuging the first tube to pellet the acid-fast bacteria in the concave tip and subsequently decanting at least <NUM>% of a first supernatant while retaining the pellet of acid-fast bacteria in the concave tip; (d) resuspending the acid-fast bacteria pellet in alcohol, optionally ethanol, to generate a first suspension; (e) transferring the suspension from the first tube to a second tube containing beads to form a second suspension; (f) agitating the second tube to break up clumps and disrupt acid-fast bacteria cells in the second suspension; and (g) incubating the second suspension for at least <NUM> minutes to inactivate the acid-fast bacteria in the test sample to form an inactivated second suspension; optionally wherein said acid-fast bacteria is Mycobacterium or Nocardia.

The liquid culture sample acquired may be from about <NUM> to about <NUM>. from about <NUM> to about <NUM>. or about <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In an exemplary embodiment, the sample taken from the positive liquid culture medium is about <NUM>. It has been found that a sample comprising at least about <NUM> from the liquid culture sample has sufficient microorganisms present to yield an accurate identification via mass spectrometry.

According to the invention, the liquid culture containing acid-fast bacteria is a sample container that has tested positive for acid-fast bacteria. For example. the sample container may culture a biological sample from a subject. If the subject is positive for acid-fast bacteria, the sample container is identified as positive via, e.g., a sensor in the container. According to the invention, the liquid culture sample is acquired at least about <NUM> hours after the sample container is identified as positive. In some embodiments, the liquid culture sample is acquired between about <NUM> hours and <NUM> hours after the sample container is identified as positive. In still further embodiments, the liquid culture sample is acquired later than <NUM> hours after the sample container is identified as positive. Allowing a sample container to continue to incubate after it has been identified as positive causes an increase in the population size of the microorganisms in the sample container. According to the invention, a minimum concentration of <NUM>. 0x10<NUM> CFU/mL is present in the sample as required biomass for acid-fast bacteria. In this way, the concentration of microorganisms in the liquid culture sample will be greater and the likelihood of an accurate identification via mass spectrometry increases. Further, some laboratories may have times during the day or week when sample containers cannot be evaluated. The instant method is flexible in the length of time that a sample container may be incubated after it has been identified as positive.

As discussed, the method of the invention includes centrifuging the sample in a tube having a body, a first end to the body having an opening, and a second end to the body having a frustoconical portion ending in a concave tip. Tuming briefly to <FIG>, an exemplary tube as described is shown. In <FIG>, the tube <NUM> includes the body <NUM>, the opening <NUM> at the first end of the body <NUM>, and frustoconical portion <NUM> ending in a concave tip <NUM> at the second end of the body <NUM> along a longitudinal axis <NUM> of the tube <NUM>. According to the invention, the body has a volume of <NUM>. As used herein, "frustoconical" means the shape of the frustum of a cone. The frustum of a cone is the basal part of a cone formed by cutting off the top by a plane parallel to the base. In some embodiments, the tube <NUM> includes a resealable cap <NUM> for securing the contents of the tube <NUM> which may be further secured via a safety lock. In some embodiments. the resealable cap may be a screw cap. In this embodiment, the screw cap seals the microorganism in the first tube to protect the user. For example, the screw cap may form a hermetic seal to reduce the chance of infection. In further embodiments, the resealable cap may be a snap fit cap and may include features so as an O-ring seal or a twist-lock.

In some embodiments, the angle of the frustoconical portion <NUM> from the longitudinal axis <NUM> is less than <NUM> degrees. For example the angle of the frustoconical portion <NUM> from the longitudinal axis can be about <NUM> degrees, about <NUM> degrees, about <NUM> degrees. about <NUM> degrees, about <NUM> degrees, or about <NUM> degrees. The angle of the frustoconical portion <NUM> relative to the longitudinal axis <NUM> assists in decanting supernatant from the tube while retaining a pelleted microorganism in the concave tip. In some embodiments, the concave tip is configured to retain the pelleted microorganism while decanting supernatant (e.g., liquid media, etc.).

In some embodiments. the first tube is centrifuged for at least about <NUM> minutes. For example, the first tube may be centrifuged for <NUM> minutes, <NUM> minutes, <NUM> minutes, etc. In an embodiment. the first tube is centrifuged at <NUM>,<NUM> x g to generate a pellet at the bottom of the tube and a supernatant above the pellet. The first tube may be centrifuged at a faster or slower rate, as determined by one of skill in the art.

According to the invention, after centrifuging the sample in the first tube. a first supematant resulting from the centrifugation is decanted from the first tube, wherein the frustoconical portion ending in the concave tip is configured to retain the pellet of acid-fast bacteria in the concave tip. According to the invention, at least about <NUM>% of the first supernatant is decanted. For example, <NUM>%, <NUM>%. <NUM>%, or <NUM>% of the supernatant is decanted from the first tube. Removal of the supernatant and retention of the pelleted microorganism is important for accurate identification of the microorganism using mass spectrometry. Removal of the supematant is important because excessive supernatant in the biological sample can interfere with the spectra produced using the mass spectrometer. Retention of the pelleted microorganism is important to ensure that sufficient microorganism is available for the mass spectrometer analysis. In some embodiments, decanting includes blotting the first tube and/or inverting the first tube for a period of time so that the supernatant can exit the opening.

After the centrifugation step (c), the acid-fast bacteria pellet can be resuspended in step (d) in the first tube with from about <NUM>µL to about <NUM> of alcohol. or with about <NUM>µL to about <NUM>µL, with about <NUM>µL to about <NUM>µL, or with about <NUM>µL. The alcohol used for resuspending the pellet can be from about <NUM>% to about <NUM>% alcohol. from about <NUM>% to about <NUM>% alcohol, or about <NUM>%. <NUM>%, <NUM>%, <NUM>% or <NUM>% alcohol. In an exemplary embodiment, the alcohol is ethanol.

According to the invention, the method includes transferring the suspension from the first tube to a second tube containing beads. According to the invention, the method includes agitating the suspension to break up clumps and/or disrupt acid-fast bacteria cells. For example, the acid-fast bacteria test sample can be subjected to mechanical disruption using a vortex or a bead beater (e.g., Bead Beater, BioSpec, Bartlesville, OK), a homogenizer that disrupts cells by agitating a sealed micro centrifuge tube containing sample, extraction solution. Typically, the beads can be any known beads that can operate to disrupt cells in a container or microcentrifuge tube. For example, the beads can be glass, ceramic, zirconia. silicon, metal, steel, tungsten carbide, garnet, sand, or sapphire beads. In one embodiment, the bead can be from about <NUM> to about <NUM> in size, for example, about <NUM> in size. In one embodiment, the beads are <NUM> glass beads. Typically, the tube is subjected to disruption by beating or vortexing the container in step (e) for about <NUM> minute to about <NUM> minutes, for about <NUM> minutes to about <NUM> minutes, for about <NUM> minutes to about <NUM> minutes, or for about <NUM> minutes or <NUM> minutes. In further embodiments. the tube is agitated using a vortex for a period of time. For example, the tube may be vortexed for at least about <NUM> minutes. In some embodiments, the tube is vortexed for <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, or longer.

After the acid-fast bacteria in the test sample have been disrupted, the tube, and thus the acid-fast bacteria (e.g., Mycobacterium or Nocardia) in the test sample, are subjected to inactivation by incubating the container for at least <NUM> minutes or for at least <NUM> minutes. In another embodiment, the incubation step (g) can be for at least <NUM> minutes to about <NUM> minutes, for about <NUM> minutes to about <NUM> minutes, or for <NUM> at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> minutes. In one embodiment, the incubation step (g) is at room temperature. In another embodiment, the incubation step (g) is at an elevated temperature, e.g., <NUM> degrees Celsius, <NUM> degrees Celsius, or <NUM> degrees Celsius.

In another aspect, the present invention is directed to further steps for protein extraction of an acid-fast bacteria test sample. In one embodiment, the acid-fast bacteria test sample subjected to the extraction steps of the present invention can be the test sample obtained from the previously described method for inactivation (i.e., the inactivated acid-fast bacteria test samples described above).

The extraction method may comprise the following steps: (h) transferring the suspension to a third tube and centrifuging the third tube to pellet the inactivated acid-fast bacteria (e.g., Mycobacterium or Nocardia) and subsequently removing a second supernatant; and (i) resuspending the inactivated acid-fast bacteria pellet to generate a solution comprising the inactivated acid-fast bacteria. In some embodiments, the inactivated acid-fast bacteria pellet is resuspended in formic acid and/or acetonitrile. Optionally, the method further comprises centrifugation of the test sample in the container after step (i) to extract cellular protein (step (j)) and pellet cellular debris. For example, the third tube can be centrifuged for <NUM> minutes at <NUM>,<NUM> x g.

In accordance with these embodiment, the pellet may be resuspended using from about <NUM>% to about <NUM>% formic acid, from about <NUM>% to about <NUM>% formic acid, or about <NUM>%. <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% formic acid. In some embodiments, after resuspending the pellet acetonitrile is added to obtain a final concentration of from about <NUM>% to about <NUM>%, to obtain a final concentration of from about <NUM>% to about <NUM>%. or to obtain a final concentration of about <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>% acetonitrile. In one embodiment, <NUM>% acetonitrile is used for this step although other concentrations of acetonitrile may be used.

In one embodiment, the pellet may be resuspended in at least about <NUM>, <NUM>, or <NUM>µL of formic acid and at least <NUM>, <NUM> or <NUM>µL of acetonitrile can be added to the resuspended pellet. In another embodiment. the pellet may be resuspended using from about <NUM>µL to about <NUM>µL of formic acid, about <NUM>µL to about <NUM>µL formic acid, about <NUM>µL to about <NUM>µL of formic acid, or about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>µL formic acid. In another embodiment, after resuspending the pellet, at least about <NUM>, <NUM> or <NUM>µL of acetonitrile are added to the resuspended pellet. For example, from about <NUM>µL to about <NUM>µL acetonitrile. from about <NUM>µL to about <NUM>µL acetonitrile, <NUM>µL to about <NUM>µL acetonitrile. or about <NUM>. <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>µL acetonitrile, may be added to the resuspended sample.

The present disclosure also provides methods for characterization and/or identification of an unknown acid-fast bacteria (e.g., Mycobacterium or Nocardia) using mass spectrometry, e.g., using matrix assisted laser desorption ionization time-of-flight (MALDI-TOF mass spectrometry). In accordance with the present disclosure, the characterization and/or identification steps may follow the inactivation and extraction steps described above.

In this aspect, the methods may further comprise the following additional steps: transferring an aliquot of the supernatant from step (k) to a mass spectrometry target slide and adding a matrix solution to the supernatant; and (l) identifying the protein profiles of the inactivated acid-fast bacteria in the third supernatant on the mass spectrometry slide by mass spectrometry to acquire one or more mass spectra of the acid-fast bacteria, and characterizing and/or identifying said acid-fast bacteria in the test sample by comparison of the measured one or more mass spectra with one or more reference mass spectra. Optionally, the transferred aliquot can be from about <NUM>µL to about <NUM>µL, or about <NUM>µL. As is well known in the art, the aliquot is typically allowed to dry and subsequently a matrix solution is added. In general, any known matrix in the art can be used. For example, in one embodiment, the matrix is alpha-cyano-<NUM>-hydroxycinnamic acid (CHCA). In accordance with the present invention, the acid-fast bacteria (e.g., Mycobacterium or Nocardia) can be identified to the family, genus, species, strain level or group/complex using, for example, MALDI-TOF mass spectrometry, as described further hereinbelow.

After the mass spectrometry plate or slide has been prepared, the slide or plate is inserted into the mass spectrometer. After the time required to pump the sample down (i.e. remove atmospheric gases from the sample so that it is in an environment of <NUM>-<NUM> to <NUM>-<NUM> torr), the sample is introduced into the ionization chamber of the mass spectrometer. The sample is aligned with the system. When optimal alignment is achieved, the nitrogen laser is pulsed. The absorption of the laser energy by the matrix causes it to ablate from the plate's surface due to the high energy deposited. As a side effect, portions of the acid-fast bacteria cells (e.g. proteins) are also vaporized and ionized in the process. These ions are accelerated to a known kinetic energy by the generation of an electrostatic field between the plate and the entrance to the mass spectrometer's flight tube. All singly charged ions. regardless of mass, will have the same kinetic energy at the entrance to the flight tube, but they will have velocities that are inversely proportional to their masses. From there, ions move down the flight tube towards the detector. and lighter ions will arrive before heavier ions (the flight tube is the mass/charge discriminator). The detector generates an electrical charge every time an ion impacts the detector. The output of the detector is digitized and the output displays mass/charge ratio on one axis and number of impacts on the other axis. In one embodiments, the protein profile of the acid-fast bacteria on the slide or plate can be interrogated using any known mass spectrometry techniques, such as MALDI-TOF mass spectrometry. desorption electrospray ionization (DESI) mass spectrometry, GC mass spectrometry, LC mass spectrometry, electrospray ionization (ESI) mass spectrometry and Selected Ion Flow Tube (SIFT) spectrometry, or other mass spectrometry technique.

In some aspects, control measurements are taken for known acid-fast bacteria, thus allowing for correlation of measured test data with characterization of the acid-fast bacteria of interest using various mathematical methods. For example, the data from samples may be compared with the baseline or control measurements utilizing software systems. More particularly, the data may be analyzed by a number of multivariate analysis methods, such as, for example, General Discriminant Analysis (GDA), Partial Least Squares Discriminant Analysis (PLSDA). Partial Least Squares regression, Principal Component Analysis (PCA), Parallel Factor Analysis (PARAFAC), Neural Network Analysis (NNA), and/or Support Vector Machine (SVM). These methods may be used to classify unknown acid-fast bacteria (e.g.. Mycobacterium or Nocardia) of interest into relevant groups based on existing nomenclature, and/or into naturally occurring groups based on the organism's metabolism, pathogenicity and/or virulence. In one embodiment, after acquisition of a one or more mass spectra for acid-fast bacteria, the one or more mass spectra can be input into the "SARAMIS" microorganism identification software (bioMérieux, Inc. Louis, MO) for analysis, and thus, for characterization and/or identification of the acid-fast bacteria.

In yet another aspect, non-spectroscopic measurements from the detection system, such as detection times and growth rates can be used to assist in the characterization and/or identification of acid-fast bacteria from the test sample.

In some aspects, characterization and/or identification of the acid-fast bacteria in the test sample need not involve identification of an exact species. Characterization may encompass the broad categorization or classification of biological particles as well as the actual identification of a single species. As used herein "identification" means determining to which family, genus. species, strain level or group/complex a previously unknown acid-fast bacteria belongs to. For example, identifying a previously unknown acid-fast bacteria to the family. genus, species, strain level or group/complex.

Tuming now to <FIG>, in one aspect a method <NUM> for inactivation, extraction, and identification of acid-fast bacteria in a liquid test sample is provided. The present invention is directed to a method for inactivation and extraction of acid-fast bacteria in a test sample, the method comprising the following sequential steps: (a) culturing a test sample containing acid-fast bacteria in a liquid culture and continuing to culture the test sample in the liquid culture for at least <NUM> hours after the test sample has tested positive for growth of the acid-fast bacteria and until a minimum concentration of <NUM>. 0x10<NUM> CFU/ml is present in the test sample culture; (b) transferring the test sample from the positive liquid culture to a first tube, wherein the first tube comprises a body having a volume of <NUM>, a first end to the body having an opening, and a second end to the body having a frustoconical portion ending in a concave tip; (c) centrifuging the first tube to pellet the acid-fast bacteria in the concave tip and subsequently decanting at least <NUM>% of a first supernatant while retaining the pellet of acid-fast bacteria in the concave tip; (d) resuspending the acid-fast bacteria pellet in alcohol, optionally ethanol, to generate a first suspension; (e) transferring the suspension from the first tube to a second tube containing beads to form a second suspension; (f) agitating the second tube to break up clumps and disrupt acid-fast bacteria cells in the second suspension; and (g) incubating the second suspension for at least <NUM> minutes to inactivate the acid-fast bacteria in the test sample to form an inactivated second suspension; optionally wherein said acid-fast bacteria is Mycobacterium or Nocardia.

In an embodiment, the method further comprises (h) resuspending the inactivated acid-fast bacteria pellet to generate a solution comprising the inactivated acid-fast bacteria. (i) extracting cellular proteins from the solution comprising inactivated acid-fast bacteria and centrifuging the solution to pellet the cellular debris;(j) transferring an aliquot of a third supernatant from step (i) to a mass spectrometry target slide; and(k) identifying protein profiles of the inactivated acid-fast bacteria on the mass spectrometry slide using a mass spectroscopy instrument, optionally wherein said acid-fast bacteria sample is identified to the family, genus, species, strain level and/or group/complex.

Turning to block <NUM>, in some embodiments the method includes taking a <NUM> sample from a positive liquid culture between <NUM>-<NUM> hours post positive result. As discussed, the volume of the sample assists in ensuring sufficient microorganisms are present in the sample to acquire an acceptable spectra using a mass spectrometry instrument. Similarly, taking the sample from the positive liquid culture between <NUM> and <NUM> hours after a positive result increases the population size of the microorganisms in the liquid culture. In some embodiments, the sample may be taken from the positive liquid culture in less than <NUM> hours. For example. see <FIG> showing that many strains of Mycobacterium can be identified in as little as two hours post-positive.

In block <NUM>, according to the invention, the sample is placed into a tube (i.e. a <NUM> tube) having a frustoconical portion ending in a concave tip. which is then centrifuged. For example, the tube can be centrifuged for <NUM> minutes at <NUM>,<NUM> x g to generate a pellet in the concave tip and a supernatant above the pellet. The supernatant is then discarded by decanting. For example. the tube may be inverted and the supernatant poured off through the opening and then the tube blotted to remove excess liquid.

In block <NUM>, the pellet is resuspended in alcohol. In some embodiments, the pellet is resuspended in <NUM>µL <NUM>% ethanol and the suspension is transferred to a second tube containing <NUM> glass beads, according to the invention.

In block <NUM>. in one embodiment the tube is bead beat and then incubated. For example, the tube may be bead beat for <NUM> minutes and then incubated for <NUM> minutes. The combination of agitation and incubation inactivates the microorganism. Alternatively, as shown in block <NUM>. in some embodiments the tube is vortexed and then incubated, such as vortexed for <NUM> minutes and then incubated for <NUM> minutes. As discussed, the incubation may be at room temperature or may be at an elevated temperature.

Tuming now to block <NUM>. in some embodiments the inactivated acid-fast bacteria present in the tube after agitation and incubation are vortexed and the suspension is transferred to an empty tube. In block <NUM>, the suspension is centrifuged and the ethanol supernatant is removed, leaving the inactivated acid-fast bacteria pelleted in the tube.

In blocks <NUM> and <NUM>, cellular proteins are extracted by the addition of <NUM>µL <NUM>% formic acid and then the addition of <NUM>µL acetonitrile. In some embodiments, the tube is vortexed after the addition of the formic acid and/or acetonitrile to pellet cellular debris.

In block <NUM>, <NUM>µL of the suspension is inoculated onto a mass spectrometry target slide, matrix is added to the target slide in block <NUM>, and the microorganism is identified using MALDI-TOF mass spectrometry in block <NUM>. This method describes an unexpected improvement in identification of microorganisms from liquid media using specific steps that address the difficulties of conducting identification from liquid media.

Turning now to <FIG>, a comparison <NUM> of tube profiles is provided. As shown in <FIG>, tube A has a frustoconical portion ending in a concave tip. This profile is in contrast to tubes B, C, D, and E. Tube A has been found to both retain the pellet in the concave tip while decanting a large percentage of the supernatant to assist in identification of microorganisms using mass spectrometry. Tube B, for example, would not be appropriate for identification because some or all of the pellet would be lost during decanting of the supernatant. The tip of tube C is not designed to retain the pellet during decanting while reducing retention of the supematant. Instead, supernatant will be retained underneath and around the pellet due to the shape of the tip. Similarly, tube D may retain the pellet but would also retain fluid beneath the pellet in the angled tip. For example, after decanting tube A, only <NUM>-<NUM>µL of media remained in the tube in one experiment, but decanting tube D resulted in <NUM>-<NUM>µL of media remaining in the tube after decanting. Tube E results in the loss of some or all of the pellet during the decanting step. Unexpectedly. tube A demonstrates significantly improved results in identifying microorganisms with a mass spectrometry instrument while addressing the difficulties of using liquid media.

In <FIG>, identification results of multiple strains including ATCC and clinical isolates of Mycobacterium species incubated in a VersaTREK® Automated Microbial Detection System are provided. In this Figure, twenty-eight different Mycobacterium strains were incubated in the VersaTREK® Automated Microbial Detection System. Each strain was incubated in a sample container using the VersaTREK® Automated Microbial Detection System, removed when the system indicated that the sample container was positive for microorganism growth, incubated for additional periods of time in the sample containers, and samples from the sample containers were intermittently treated via the method disclosed herein to inactivate and extract the proteins from Mycobacterium cells. The mycobacterial proteins were then analyzed via MALDI-TOF mass spectrometry to determine if the post-positive sample had sufficient biomass and lack of contamination to yield accurate mass spectra. The results shown in <FIG> demonstrate that the method disclosed herein is able to inactivate and extract mycobacterial proteins in a short period of time after the system identifies the sample container as positive for microorganism growth, and accurately produce spectra that match with <NUM>% agreement to the expected species level identification. All strains tested were correctly identified when processed within <NUM> hours post -positivity, and all but three of the strains were identified within <NUM> hours. Surprisingly, many of the strains, including high prevalence strains such as M. avium and M. intracellulare, had correct identification when processed within <NUM> hours post-positivity.

<FIG> shows identification results of various Mycobacterium strains incubated in a Bactec™ MGIT™ <NUM> Mycobacterial Detection System. Similar to <FIG>. <FIG> demonstrates that the method is capable of inactivating, extracting, and identifying mycobacterial proteins quickly post-positivity. For example. all but two of the strains had sample spectra that were a <NUM>% match to the expected species level identification within <NUM> hours. The two remaining strains had <NUM>% agreement to the expected species level identification within <NUM> hours. This rapid inactivation, extraction, and identification of mycobacterial proteins will impact the treatment of infections related to mycobacteria.

In <FIG>, identification results of various Mycobacterium strains incubated in a BacT/ALERT® 3D instrument are provided. Again, the samples are incubated in sample containers, the instrument determines when the sample is positive for microorganism growth, and samples are taken from the positive sample containers intermittently for testing via the disclosed method. In this example, all strains had sample spectra that were a <NUM>% match to the expected species level identification within <NUM> hours.

In another aspect, a kit for use with the method described in <FIG> and elsewhere herein is provided. In some aspects, the kit includes a first tube having a body. a first end to the body having an opening, and a second end to the body having a frustoconical portion ending in a concave tip, wherein the first tube has a volume of at least <NUM>; a solution of alcohol; a solution of formic acid; and a solution of acetonitrile. In further embodiments, the kit may include <NUM> glass beads and/or blotting paper. Similarly, the kit may include a stand for decanting the first tube or instructions to the method described herein and for which the kit is designed to be used.

In the drawings, the thickness of lines. layers, features, components and/or regions may be exaggerated for clarity. In addition, the sequence of operations (or steps) is not limited to the order presented in the claims unless specifically indicated otherwise.

It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features. steps, operations, elements, and/or components. but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. While the term "comprising" may be used herein, it should be understood that the objects referred to as "comprising" elements may also "consist of" or "consist essentially of" the elements. As used herein, phrases such as "between X and Y" and "between about X and Y" should be interpreted to include X and Y. As used herein, phrases such as "between about X and Y" mean "between about X and about Y. " As used herein, phrases such as "from about X to Y" mean "from about X to about Y.

The present invention is described in part with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products. such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

Claim 1:
A method for inactivation and extraction of acid-fast bacteria in a test sample, the method comprising the following sequential steps:
(a) culturing a test sample containing acid-fast bacteria in a liquid culture and continuing to culture the test sample in the liquid culture for at least <NUM> hours after the test sample has tested positive for growth of the acid-fast bacteria and until a minimum concentration of <NUM>.0x10<NUM> CFU/ml is present in the test sample culture;
(b) transferring the test sample from the positive liquid culture to a first tube, wherein the first tube comprises a body having a volume of <NUM>, a first end to the body having an opening, and a second end to the body having a frustoconical portion ending in a concave tip;
(c) centrifuging the first tube to pellet the acid-fast bacteria in the concave tip and subsequently decanting at least <NUM>% of a first supernatant while retaining the pellet of acid-fast bacteria in the concave tip;
(d) resuspending the acid-fast bacteria pellet in alcohol, optionally ethanol, to generate a first suspension;
(e) transferring the suspension from the first tube to a second tube containing beads to form a second suspension;
(f) agitating the second tube to break up clumps and disrupt acid-fast bacteria cells in the second suspension; and
(g) incubating the second suspension for at least <NUM> minutes to inactivate the acid-fast bacteria in the test sample to form an inactivated second suspension;
optionally wherein said acid-fast bacteria is Mycobacterium or Nocardia.