Patent Publication Number: US-2022226629-A1

Title: Device for delivery of antimicrobial agent into a medical device

Description:
This application is a continuation of U.S. Utility application Ser. No. 15/850,351, filed Dec. 21, 2017, which is a continuation of U.S. Utility application Ser. No. 13/547,572, filed Jul. 12, 2012 (now U.S. Pat. No. 9,849,276), which claims the benefit of U.S. Provisional Application No. 61/506,979, filed Jul. 12, 2011, the contents of which are herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to medical devices for preventing infectious organisms from entering and occupying the lumen of catheters and drainage tubes, and more particularly, to systems, methods, and articles for delivering antimicrobial agents into the lumen and near the entry region (at the proximal end) of catheters and drainage tubes. 
     BACKGROUND OF THE INVENTION 
     Hemodialysis catheters allow patients with renal disease to have toxins removed from their bloodstream. Without the use of catheters, many of these patients would not survive. However, long-term hemodialysis catheters have a serious drawback in that a significant percentage of catheters fail due to infection, resulting in elevated mortality rates and large annual healthcare costs associated with treatment. Furthermore, bloodstream infections are a leading cause of death in the United States, and many of those infections are attributable to vascular access devices such as hemodialysis catheters. The mortality rate associated with such infections is considerable. 
     Therefore, a need exists for a manner in which infections relating to long-term hemodialysis catheters can be reduced. 
     SUMMARY OF THE INVENTION 
     The present application is directed, in part, to a device for delivering an antimicrobial agent into the lumen of a trans-dermal catheter. The device comprises an elongate member configured for insertion into the proximal end of a catheter and an antimicrobial composition positioned to be delivered into the catheter. At least a portion of the antimicrobial composition is delivered to the exterior of the proximal end of the catheter upon insertion of the elongate member into the proximal end of the catheter. 
     The application is also directed to a device for delivering an antimicrobial agent into the lumen of a trans-dermal catheter, the device comprising a capping member configured for placement over the proximal end of a catheter; and an antimicrobial composition positioned on the interior of the capping member. 
     The application is further directed to a method of applying an antimicrobial to the proximal end of a trans-dermal catheter. The method includes providing a transdermal catheter; filling at least a portion of the proximal end of the transdermal catheter with a lock solution; clamping the transdermal catheter near its proximal end to restrict flow of the lock solution into the distal end of the transdermal catheter; and inserting an elongate member into the proximal end of the transdermal catheter such that the elongate member sufficiently displaces lock solution so as to have the lock solution flow from the proximal end of the catheter. The elongate member includes or incorporates an antimicrobial material. 
     This summary is not intended to be limiting of the invention. The invention is further described in the following detailed description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be more completely understood in connection with the following drawings, in which: 
         FIG. 1A  is a perspective view of a dual-shield with two caps made in accordance with the preferred implementation of the invention. One cap is inserted into the dual shield; the other cap is not inserted. 
         FIG. 1B  is a side cross section view of two caps inserted into a dual-shield and is made in accordance with the preferred implementation of the invention. 
         FIG. 2A  is a perspective view of an elongate member and mono shield made in accordance with an implementation of the invention. The cap is shown not inserted into the mono shield. 
         FIG. 2B  is a side cross section view of a cap inserted into a mono shield made in accordance with an implementation of the invention. 
         FIG. 3A  is a perspective view, looking from the distal end of a cap, made in accordance with the preferred implementation of the invention. 
         FIG. 3B  is a side cross section view of a cap made in accordance with the preferred implementation of the invention. 
         FIG. 4A  is a perspective view of two caps made in accordance with the preferred implementation of the invention, and a catheter. The caps are shown inserted into the catheter. 
         FIG. 4B  is a side cross section view of a cap made in accordance with the preferred implementation of the invention, and inserted into a catheter. 
         FIG. 4C  is an end cross section view of a cap made in accordance with the preferred implementation of the invention, and inserted into a catheter. 
         FIG. 5A  is a side cross section view of a cap made in accordance with the preferred implementation of the invention, prior to cap being inserted into a catheter. 
         FIG. 5B  is a side cross section view of a cap made in accordance with a preferred implementation of the invention, as the cap is being inserted into a catheter. 
         FIG. 5C  is a side cross section view of a cap made in accordance with a preferred implementation of the invention, with the cap fully inserted into a catheter. 
         FIG. 6  is a side cross-section view of a cap with a seal at the distal end of the retaining ring made in accordance with an implementation of the invention, inserted into a catheter. 
         FIG. 7  is a side cross-section view of a cap with foam along the threads of the retaining ring made in accordance with an implementation of the invention, and inserted into a catheter. 
         FIG. 8A  is a side cross-section view of a cap with a swellable tip made in accordance with an implementation of the invention, inserted into a catheter. The tip is shown in its unswollen state. 
         FIG. 8B  is a side cross-section view of a cap with a swellable tip made in accordance with an implementation of the invention, inserted into a catheter. The tip is shown in its swollen state. 
         FIG. 9  is a side cross-section view of a cap not containing an elongate member made in accordance with an implementation of the invention. 
         FIG. 10A  is a perspective view, looking from the distal end of a cap, made in accordance with a preferred implementation of the invention. 
         FIG. 10B  is a perspective view, looking from the distal end of an insert, made in accordance with a preferred implementation of the invention. 
         FIG. 10C  is a perspective view, looking from the proximal end of an insert, made in accordance with a preferred implementation of the invention. 
         FIG. 10D  is a perspective view, looking from the distal end of a retaining ring, made in accordance with a preferred implementation of the invention. 
         FIG. 10E  is a side section view of a retaining ring made in accordance with a preferred implementation of the invention. 
         FIG. 10F  is a side cross section view of a cap made in accordance with a preferred implementation of the invention. 
         FIG. 11  is a table showing the effect of interference between a retaining ring and shoulder upon ring-insert torque. 
         FIG. 12  shows concentration of microbes grown in various catheter conditions. 
         FIG. 13  shows a chart of survival analysis of bacteria-free catheters under various conditions. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention relates to devices, systems, and methods for treating, preventing and eliminating infectious organisms in medical devices, such as catheters and drainage tubes, and preventing the organisms from entering the bloodstream. The devices, systems, and methods deliver antimicrobial agents into the lumen and near the entry region of catheters and drainage tubes. The following detailed description presents a description of certain specific embodiments to assist in understanding the claims. However, one may practice the present invention in a multitude of different embodiments as defined and covered by the claims. 
     The present invention includes, in certain implementations, methods and devices for preventing organism proliferation and biofilm formation in catheters so that organisms aren&#39;t able to exit the catheter and enter the bloodstream of a patient. The device and system prevents, or reduces the number of, organisms reaching the bloodstream by employing any or all of the following three prevention methods: 1) physically blocking migration of organisms outside the catheter, 2) killing organisms along the threads, end face and luer connector at the proximal end (outside of the body) of the catheter using an antimicrobial, and/or 3) killing organisms within a confined region of the catheter using an antimicrobial agent and/or a physical barrier in the catheter lumen. A fourth mode of action, scrubbing the catheter wall (to physically remove organisms adhered to the catheter&#39;s proximal end (thread and/or end face) and/or the interior wall section upon removing the cap from the catheter) may also be used in conjunction with the other methods and devices, or independently in certain implementations. 
     In a first aspect, the present invention includes an organism barrier at the external end of the catheter, also referred to herein as the proximal end of the catheter. This barrier provides a seal to keep organisms from reaching the end face and luer portions of the connector on a catheter. This can be accomplished, for example, by using either of the following features: First, placing an elastomeric flap or gasket (i.e., silicone, neoprene, polyurethane, etc.) that is positioned at the end of the cap&#39;s connector or, alternatively, along the inner wall of the cap&#39;s locking-ring. The flap preferably makes a fluid tight seal against the outer wall of the catheter&#39;s connector, thereby decreasing the likelihood of microbial incursion and preventing microbial growth. Second, placing foam, either closed cell or open cell that preferably contains an antimicrobial, along the inner wall of the cap&#39;s retaining ring and/or at the most proximal location in the cap such that it will abut and seal against the proximal end of the catheter&#39;s connector surface (also called the end face). 
     An embodiment using an antimicrobial agent along the cap&#39;s tread region, but not containing an organism barrier, can also be used to reduce the number of organisms that can enter the catheter. This reduction in the number of organisms that can enter the catheter is accomplished by killing organisms within the tread and end face region. The cap is optionally designed to transfer antimicrobial agent from the cap to the catheter threads. This is accomplished by displacing fluid from the catheter into the thread region of the connector. The elongate member and luer, when entering the catheter, displace the catheter&#39;s fluid, causing the fluid to flow out into the thread region between the connector and the cap. 
     Antimicrobial agent dissolves in the fluid, causing the fluid to become saturated with antimicrobial agent. The antimicrobial fluid produces an effective antiseptic region, killing organisms on the connector. Furthermore, as the fluid dries, antimicrobial precipitates from the fluid and is deposited onto the catheter threads and end face. This process is repeated every time a new cap is placed onto the catheter, thus replenishing the antimicrobial agent on the catheter&#39;s proximal region with every new cap. 
     In a second aspect, the invention is directed to adding of an antimicrobial along a luer connector. This can be accomplished, for example, by coating a male luer connector with various antimicrobial agents. 
     In a third aspect, the invention is directed to an antimicrobial agent inside the catheter. The antimicrobial can be delivered as a coating that elutes from a coated elongate member, that is coated on (or impregnated into) a elongate member (such as 250 μg of chlorhexidine acetate in a layer approximately 2 μm thick along a 17 mm long×1.9 mm diameter elongate member/rod). The elongate member has the added benefit of displacing fluid from within the catheter as it is inserted, thereby transferring the solution to the outer proximal region of the catheter connector (end face and treads). Antimicrobial agent from the cap dissolves into the displaced fluid, and thereby disinfecting the proximal end of the connector. Furthermore, when the fluid dries, it deposits a coating of chlorhexidine acetate or other appropriate antimicrobial on the connector as described above. As an alternative to using the elongate member, the chlorhexidine acetate or other antimicrobial agent may be delivered by a coating on a luer tip (such as 250 μg of chlorhexidine acetate in a layer that is approximately 20 μm thick). A minimum of 10 μg of chlorhexidine acetate on the elongate member is effective for many organisms in some implementations. A desirable minimum of greater than 100 μg is effective for most organisms, and a further desired minimum of 250 μg is highly effective against all of the major organisms. 
     Types of antimicrobial agent can include chlorhexidine base, chlorhexidine acetate, chlorhexidine gluconate, EDTA, silver sulfadiazine, or Taurolidine; or combinations thereof. Other antimicrobial agents may also be used. Chlorhexidine acetate is preferred because it has a long history of human use, with a well understood safety and efficacy profile. 
     Typically these methods are also used in conjunction with confinement of the antimicrobial in the catheter, such as by relying on a catheter clamp to confine the antimicrobial agent in a portion of the proximal end of the catheter (that portion of the catheter outside of a patient and in particular that portion nearest the connector on the catheter by which fluids enter and leave the catheter). Extension tube clamps are part of each hemodialysis catheter and are currently used to confine lock solutions that are used to help ensure catheter patency. Using the existing clamp methodology, the risk of air embolus and lock solution entering the patient is very small and consistent with the current state of the art for conducting hemodialysis procedures. In other medical devices, such as catheters that do not possess catheter clamps, a swellable cap tip or other confinement technique, such as those described in United States patent application publication number US 2010/0106103 A1, may be used. 
     Organism mechanical removal can also be utilized. In this regard, a portion of the elongate member can scrap the catheter wall upon removal, such as by having ribs incorporated into the elongate member. In some implementations, after placing the elongate member into the catheter, anisotropic swelling moves ribs (or other projections) against wall, which provides a tighter fit against the wall after swelling and further promotes mechanical removal of the organisms. Also, it is possible for the tip of the elongate member to swell (or other portions such as ribs to swell), or swelling along the length of the elongate member. Preferably the elongate member&#39;s unswollen diameter is smaller than the catheter lumen when the elongate member is being inserted, but swells to conform to the inner shape (or larger) of the catheter lumen to enhance the mechanical removal of the organisms during removal. Various polyurethanes or other material may be used to produce suitable anisotropic swelling and mechanical stability; more specifically, Lubrizol 1065D is suitable for a non-swelling elongate member and TG-500 is suitable for an anisotropic swelling (or isotropic swelling) tip which may be bonded with each other using heat bonding or other suitable methods. 
     An embodiment of the invention, herein referred to as “the cap”, contains an elongate member that can be inserted into a medical device, such as a catheter or a drainage tube, for the prevention and treatment of infectious organisms within the medical device and in proximity to the elongate member, and further prevents the migration of infectious organisms into the body by providing an antimicrobial and/or physical barrier. For the sake of simplicity, the term “catheter” is used for all medical devices in which the present invention can be inserted and used to treat, prevent, and eliminate infectious organisms. The cap may be removed from the catheter to allow the catheter to be used in a dialysis procedure or other procedure. After the procedure is complete, a new cap may be used to seal and protect the catheter. The removal of one cap and the replacement with a new cap may be repeated an indefinite number of times. With each new cap, the antimicrobial agent inside and outside of the catheter is reestablished. Another aspect of the invention is that antimicrobial agent is transferred from the cap to the catheter with each use. 
     An example embodiment includes an elongated rod comprising a suitable material into which an antimicrobial agent has been incorporated. The term “antimicrobial,” as used here, includes any substance or substances that kills or inhibits the growth of organisms such as bacteria, fungi, protozoa, viruses, etc. It should also be noted that there can be one or more antimicrobial agents used. Therefore, throughout this document, antimicrobial agent refers to one or more antimicrobial agents. While the invention may be used in a variety of medical devices, a catheter, and more specifically a long-term hemodialysis catheter, will be used to describe the use of the invention. The use of these examples is not meant to confine or limit the use of the invention in other types of catheters or medical devices, such as peritoneal dialysis catheters, urinary catheters, PICC lines, central venous catheters, feeding tubes and drainage catheters. 
     One useful application of the invention is in preventing infections in people with hemodialysis catheters. The present invention prevents or eliminates infectious organisms on connector and the luminal wall of a catheter by providing a means for the prolonged presence of an antimicrobial agent and/or providing a means for periodically scrubbing the luminal wall of the catheter to remove the biofilm in which infectious organisms proliferate. 
     Competing methods for preventing, eliminating, and treating infectious organisms in the lumen of a catheter are in limited use. One method uses an antimicrobial coating on or in the internal wall of the catheter. The issues that have precluded widespread use include the antimicrobial coating eventually wearing off, losing potency, or becoming covered with blood products, rendering the coating ineffective. When antibiotics are used as the antimicrobial agent, there is an additional concern regarding the emergence of resistant organisms to antibiotics and the risk of anaphylaxis to the antibiotics. Another method for treating infectious organisms in the lumen is the use of an antibiotic or antimicrobial liquid, known as a locking agent or locking solution. In this method, an antimicrobial fluid is injected into the catheter, and a cap is attached to the hub of the catheter to prevent the fluid from leaking out of the catheter and to prevent infectious organisms from entering into the lumen. 
     One issue precluding widespread use of this method is concern for the emergence of resistant organisms if an antibiotic agent is used. This concern may be virtually eliminated, however, by using a non-antibiotic antimicrobial, such as taurolidine. Another issue when dialysis catheters are filled with locking solutions is that the locking solution spills into the bloodstream. This occurs for two reasons. First, when the catheter is filled with a volume equal to the catheter volume, a significant portion of the fluid leaks out due to the nature of the laminar flow profile in the catheter. Second, blood flow by the tip/distal end results in the injected catheter locking solution being pulled out due to the Venturi effect, and density differences between the lock solution result in spillage of the solution into the bloodstream. It has been reported that 60% or more of the locking solution is spilled into the bloodstream in the first few hours after instillation. Accidental overdosing, either from injecting too much volume or too high of concentration of the locking solution, can cause additional spillage into the bloodstream. Spillage has resulted in adverse events, including death. For instance, spillage has resulted in death from transient hypocalcemia when a citrate solution was used. In addition, other adverse events may occur as some types of locking solutions may build up in the body. 
     In the case of using the cap with dialysis catheters, the present invention is designed to be replaced regularly after each dialysis session, approximately three times per week. This replenishes the antimicrobial agent with each replacement, resulting in a consistent and high concentration of antimicrobial agent present within and upon the catheter on an ongoing basis resulting in decreased risk of infection. However, the confinement method, such as clamps, as used in conjunction with the invention, prevents a significant amount of antimicrobial agent from leaking into the bloodstream on a regular basis. 
     In addition, separation between the antimicrobial agent and blood can result in lower infection rate, fewer side effects, and less risk of developing resistant bacteria because a non-antibiotic antimicrobial is used. In certain embodiments, the present invention creates a physical barrier between the blood and the antimicrobial agent. The barrier greatly reduces the exchange of antimicrobial agent with blood circulating in the body, resulting in fewer side effects from the antimicrobial agent. This can result in a more consistent level of antimicrobial agent along the length of the catheter adjacent to the cap. Additionally, the barrier reduces the amount of antimicrobial agent entering the bloodstream, thus reducing the risk of an adverse reaction to the agent or developing organisms resistant to the antimicrobial agent. In comparison, it is well-known that liquid locking agents can and do routinely migrate into the bloodstream, and the blood can migrate into the catheter, thus reducing the effectiveness of the antimicrobial agent, increasing the possibility of bacteria entering the bloodstream and increasing the rate of thrombosis in the catheter. The act of flushing the catheter lumen with a fluid agent into the lumen will result in the removal of blood from the lumen and thus reduce the risk of thrombosis. If the liquid agent is an anti-thrombotic lock, such as heparinized saline or saline with 4% sodium citrate, the risk of thrombosis is further reduced. The use of a confinement means, as described in the present invention as a swellable elongate member tip, swellable elongate member, or catheter clamp, prevents the blood from reentering the lumen and results in a lower risk of thrombosis in the lumen. 
     A further aspect of the invention relates to protecting the caps from contamination prior to use and during handling in order to keep the elongate member and luer sterile prior to insertion into the catheter. A shield over the elongate member and luer may be used. A standard shield, which protects one luer and elongate member, is suitable for keeping one elongate member and luer sterile. A novel shield is hereafter described which improves handling while maintaining sterility protection, and facilitates low-cost injection molding. The novel shield holds two caps within one shield body, where the two caps are held 180 degrees opposed in an axially offset manner with at least a portion of the two elongate members axially overlapping one another, with a physical barrier between the two caps. The shield may have threads to provide a means for removably attaching the caps to the shield. This novel configuration allows the user to hold one piece rather than two, thus easing handling and decreasing the risk of dropping the caps. The barrier between the two caps ensures that, when one cap is removed from the shield, that the other cap remains sterile. The caps, secured within the shield, may be packaged in a pouch using a suitable packaging material, such as a metal film with a polymer laminate to facilitate heat sealing. The metal layer is useful to minimize adverse effects of humidity. The device, inside the pouch, may be sterilized using gamma radiation or other suitable sterilization method. Gamma radiation has the advantage of effectively sterilizing the product while it is contained within moisture-proof packaging. 
     This summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which is not to be taken in a limiting sense. The scope of the present invention is defined by the appended claims and their legal equivalents. 
     Research and development into preventing catheter-related bloodstream infections (CRBSI) over the last twenty years has been focused on methods for killing the bacteria along the inside and outside length of the catheter. This research has resulted in success at reducing the incidence of CRBSI in some catheter types. For instance, commercially successful antimicrobial coated catheters have resulted in a decrease in the incidence of infection in applications that use short-term (non-tunneled) catheters. However, these coating wash off with use and therefore are not effective for long-term applications. The use of long-term (tunneled, cuffed) hemodialysis catheters result in approximately 2.3 bloodstream infections every 1000 catheter days. Said another way, a patient dialyzing with a hemodialysis catheter can expect to develop a bloodstream infection, on average, every 14 months. To fix this remaining problem, much of today&#39;s research is focusing on ways to eliminate biofilm within catheters and on ways to produce longer lasting antimicrobial coatings that are capable of killing organisms within catheters. 
     Infectious organisms typically colonize a catheter in three distinct ways. First, the infectious organisms may colonize the catheter by traveling in the bloodstream and eventually adhering to the catheter. This form of transmission is believed to be rare. Second, the infectious organisms may colonize the catheter by traveling along the outer wall of the catheter after entering at the catheter&#39;s body exit site. This method of infection transmission has been greatly reduced by tunneling the catheter under the skin for several centimeters, and by the addition of a cuff on the outer wall of the catheter. Body tissue grows into the cuff and creates a barrier for infection. Third, the infectious organisms may colonize the inner lumen of the catheter, entering at the hub and/or adaptor of the catheter connector, eventually migrating down the lumen of the catheter to the bloodstream. This method of infection transmission is a leading cause of bloodstream infections in patients with long-term indwelling catheters. Therefore, a need exists for improved devices, systems, and methods for eliminating, treating, and preventing such contamination. 
     The present invention prevents, reduces and can even eliminate infectious organisms from the entry region of a catheter or tube, and from within the inner luminal surface of a catheter or other similar medical devices by providing a means for the prolonged presence of an antimicrobial agent and/or providing a means for periodically scrubbing the entry region and/or lumen of the catheter or other medical device to remove the infectious organisms and the biofilm in which infectious organisms proliferate. 
     The present invention includes methods and devices for killing organisms and preventing organism proliferation and biofilm formation in catheters so that organisms aren&#39;t able to exit the catheter and enter the bloodstream of a patient. The article of the present invention prevents, or reduces the number of, organisms reaching the bloodstream by employing any or all of the following three prevention methods: 1) physically blocking migration of organism outside the catheter, 2) killing organisms along the threads, end face and luer connector (inside and outside of the connector) at the proximal end (outside of the body) of the catheter using an antimicrobial, and/or 3) killing organisms within a confined region of the catheter using an antimicrobial agent and/or a physical barrier in the catheter lumen. A fourth mode of action, scrubbing the catheter wall (to physically remove organisms adhered to the interior wall section upon removing the cap from the catheter) may also be used in conjunction with the other methods and devices. 
     As noted above, the invention is directed in part to an antimicrobial agent inside the catheter. The antimicrobial agent can be delivered as a coating that elutes from a coated elongate member, that is coated on, or impregnated into, an elongate member (such as 250 μg of chlorhexidine acetate in a layer approximately 2 μm thick along a 17 mm long×1.9 mm diameter elongate member/rod). The elongate member has the added benefit of displacing fluid from within the catheter as it is inserted, transferring the solution to the outer proximal region of the catheter connector (end face and treads). Antimicrobial agent from the cap dissolves into the displaced fluid, and thereby disinfecting the proximal end of the connector. Furthermore, when the fluid dries, it deposits a coating of chlorhexidine acetate or other appropriate antimicrobial on the connector as described above. As an alternative to using the elongate member, chlorhexidine acetate or other antimicrobial agent may be delivered by a coating on a luer tip (such as 250 μg of chlorhexidine acetate in a layer that is approximately 20 μm thick). The luer portion is also coated with an antimicrobial agent (such as 50 μg of chlorhexidine acetate in a layer that is approximately 0.4 μm thick). It is also possible to inject an antimicrobial agent into the catheter using a syringe, or to deliver antimicrobial agents by way of the connector tip cavity (dry dissolvable amount, applicable for Citrate or others requiring large amounts of antimicrobial agent). 
     Referring now to the figures, example implementations of the invention are shown. Figure IA shows an exploded view of a dual shield system  10 ″ that includes an arterial cap  20 ′, a venous cap  20 ″ and a shield  50 ″; the colors are typically chosen to match the standard colors used in hemodialysis: red for the arterial cap  20 ′ and blue for the venous cap  20 ″. The dual shield system  10 ″ contains two caps within the same shield  50 ″. The shield  50 ″ provides for easier handling because there are fewer parts to handle and hold. The dual shield system  10 ″ is packaged within a heat-sealed foil-pouch (not shown) and gamma sterilized. The foil-pouch is opened at the clinic immediately before use of the caps. The cap threads  41  removably engage the dual shield threads  59  to allow easy removal of the caps  20 ′,  20 ″ from the shield  50 ″. The flattened side  57  creates a convenient means for gripping the shield as the caps  20 ′,  20 ″ are removed. In addition, the flattened side  57  disrupts the rotational symmetry of the shield  50 ″, thus making the shield system  10 ″ resistant to rolling onto the floor or being dropped. 
       FIG. 1B  shows a cross section of a dual shield system  10 ″ with an arterial cap  20 ′ and a venous cap  20 ″ each inserted into a shield  50 ″. The shield  50 ″ is designed to keep the caps  20 ′,  20 ″ axially offset as shown by the arterial cap axis  54 ′ and the venous cap axis  54 ″. The offset axis is advantageous over a coaxial design because it decreases the length of the system  10 ″, allowing it to fit into a shorter pouch and making it easier to handle. In addition, the caps  20 ′,  20 ″ are 180 degrees opposed from each other, thus making the retaining rings  40 ′,  40 ″ physically separated from one another. This is makes the retaining rings  40 ′,  40 ″ easier to grasp because the arterial retaining ring  40 ′ does not physically block finger access to the venous retaining ring  40 ″, and vice versa. The shield  50 ″ provides protection to the caps  20 ′,  20 ″ and further aids maintenance of sterility prior to use because each of the caps  20 ′,  20 ″ are separated by a wall  56 ″. In an example embodiment, the most proximal portion  31 ′ of the male luer  31  contacts the receiving edge  58  of the dual shield  50 ″. The rest of the male lure  31  does not contact the wall  56 ″, and thereby minimizes the risk of removing the antimicrobial coating on the male luer  31 . Typically the elongate member  33  also does not contact the wall  56 ″ so as to minimize the risk of removing the antimicrobial coating. 
       FIG. 2A  shows a perspective view of a mono shield system  10 ′ with a cap  20 , and a shield  50 ′. The shield  50 ′ contains one cap within the housing. The mono shield system  10 ′ is packaged within a heat-sealed foil-pouch (not shown) and gamma sterilized. The foil-pouch is opened at the clinic immediately before use of the cap. The cap threads  41  removably engage the mono shield threads  59  to allow easy removal of the cap  20  from the mono shield  50 ′. 
       FIG. 2B  shows a cross sectional view of a mono shield system  10 ′ with a cap  20  inserted into a mono shield  50 ′. The mono shield  50 ′ provides protection to the cap  20  and further ensures that sterility is maintained prior to use. This is accomplished by enclosing the cap  20  by a wall  56 ″. In an example embodiment, the most proximal portion  31 ′ of the male luer  31  contacts the receiving edge  58  of the mono shield  50 ′. The rest of the male lure  31  does not contact the wall  56 ′, and thereby minimizes the risk of removing the antimicrobial coating on the male luer  31 . The elongate member  33  also preferably does not contact the wall  56 ′ in order to minimize the risk of removing the antimicrobial coating. 
       FIG. 3A  shows a cap  20  made in accordance with an example implementation of the invention. The cap  20  can be injected molded as a single unit out of a thermoplastic polymer resin to allow high volume production at low manufacturing costs. Suitable polymer will produce a durable part such that the elongate member  33  may be bent without breaking. Polymers with a minimum elongation at break of 100% are preferred. In addition, the polymer will typically allow a solvent (which is used in the antimicrobial coating process) to wet the surface evenly until the solvent evaporates, and the antimicrobial agent should adhere well to the surface such that the coating does not flake or fall off during handling. Various polymer materials may be used that meet these requirements, such as polyester, nylon, polyetherimide, polypropylene, polyvinyl chloride or other similar materials. Alternatively, the elongate member  33  may be manufactured using a dissolvable material which is impregnated with an antimicrobial agent, thus the antimicrobial is released into the solution when the elongate member  33  dissolves. 
     Portions of the cap  20  are typically coated and/or impregnated with an antimicrobial agent. In one embodiment, the antimicrobial agent is applied as a coating, with different amounts optionally applied to the elongate member  33 , the male luer  31 , and the cap threads  41 . The antimicrobial agent can also be incorporated within the bulk polymer material, but coating the surface is preferred because surface coatings can generally be released into solution more rapidly than bulk agents; additionally surface coatings tend to require less overall antimicrobial agent than bulk agents because the antimicrobial agent on the surface is more readily dissolved. In some implementations a combination of surface coatings and incorporation into bulk polymer materials is used. 
     Suitable methods of coating the cap  20  are spraying and dipping, with spray coating being desirable because the amount of antimicrobial agent applied to each region (elongate member  33 , male luer  33 , and cap threads  41 ) can more easily be adjusted without affecting the amount located on other regions. 
       FIG. 3B  shows a cross section of a cap  20  made in accordance with an embodiment of the invention. The length and diameter of the elongate member  33  is sized to fit into a medical device. In the embodiment described herein, the catheter is a hemodialysis catheter. The male lure  31  and the cap threads  41  can be manufactured in accordance with the International Organization for Standardization standard ISO 594-2:1998(E) to be compatible with all hemodialysis catheters which are made according to the standard. 
       FIG. 4A  depicts a hemodialysis catheter  70  for use in conjunction with an embodiment of invention, and is shown with an arterial cap  20 ′ in the arterial hub  72 ′, and a venous cap  20 ″ in the venous hub  72 ″. When used with a hemodialysis patient, the two-lumen tube  87  is partially tunneled below the patient&#39;s skin, from the upper chest to the jugular vein. The two-lumen tube  72 ″ enters the jugular vein and continues until the catheter tip  89  is in the region of the right atrium of the heart. The arterial lumen  88 ′ runs inside the catheter  70  from the arterial hub  72 ′ until exiting at the catheter tip  89 . The venous lumen  88 ″, similarly, runs inside the catheter  70  until it exits near the catheter tip  89 . If bacteria or fungus are in either or both lumens  88 ′,  88 ″, these infection-causing organisms may enter the bloodstream and result in a systemic bloodstream infection, and therefore prevention of the entry and growth of microorganisms into the catheter  70  is important. The catheter contains a junction  86 , where the extension tubes  80  transition from two tubes with two lumens into one tube with two lumens; the two lumens  88 ′,  88 ″ run the entire length of the catheter  70 , from hub  72 ′,  72 ″ to catheter tip  89  without fluidly connecting with the other lumen. The arterial hub  72 ′ is attached to the proximal end of one extension tube  80 , and the venous hub  72 ″ is attached to the proximal end of the other extension tube  80 . In the depicted embodiment, a clamp  84  is positioned on each of the extension tubes  80 , allowing the flow in the lumen to be blocked or opened. In practice, the clamps  84  are closed except during a dialysis session or other transferring of fluids within the catheter  70 . The clamps  84  are typically repositioned each time the clamps  84  are opened in order to minimize the risk of damaging the extension tube  80  through multiple clamping in the same location. 
     In reference to  FIG. 4B , the clamp  84  is shown located in close proximity to the hub  72 . The clamp  84 , when closed, creates a pinch point  85  which blocks the fluid flow in the lumen. Preferably the elongate member  33  will be short enough to ensure that the clamp  84  does not clamp onto the elongate member. In addition, the elongate member  33  must possess a small enough diameter to ensure that it can physically fit within the hub lumen  79 . In embodiments where the elongate member  33  is long enough to enter the extension tube  80 , the diameter of the extension tube must also fit within the extension tube lumen  82 . The elongate member  33  should preferably be stiff enough to allow for insertion into the hub  72  without requiring sheaths, tubes or other insertion aids. 
     The surface area of the elongate member  33  should be large enough to allow for the desired amount of antimicrobial agent to be coated on the surface using spraying or dipping operations (or other application methods, including incorporation directly into the elongate member). The surface area is generally sized to produce an acceptable dissolution rate such that the antimicrobial agent enters the lock solution  90  at an acceptable rate and dosage. It is desirable for the antimicrobial agent to reach an effective level within an hour of the cap  20  being inserted into the catheter  70 . 
     If the elongate member extends into the pinch point  85  of the clamp  84 , it can potentially cause damage or leaking of the lock solution  90 . Therefore the length of the elongate member  33  should be sufficiently short to ensure that it does not reach the pinch point  85  of the clamp  84 . Suitable diameters for the elongate member  33  include 1.0 mm to 2.0 mm; and 1.7 mm to 1.9 mm. A suitable length includes less than 20 mm for the elongate member  33 , alternatively less than 30 mm, less than 40 mm, or less than 10 mm. A particularly desirable length is 17 mm to 19 mm, but can vary for use with various catheters. 
     In reference to  FIG. 4C , an embodiment is depicted showing the end section view A-A as indicated in  FIG. 4B , the cap  20  is shown fully inserted into the catheter hub  72 . When fully inserted, the male luer  31  contacts the female luer  75  to create a fluid tight seal. The cap threads  41  engage the catheter threads  78  to retain the cap  20  on the hub  72 . However, after the cap  20  is fully inserted into the hub  72 , a void  94  is present between the retaining ring  40  and the hub  72 . This void  94  can be a pathway for pathogenic organisms to travel along, thus allowing contamination of the hub surfaces with pathogenic organisms in the region between the retaining ring  40  and the hub  72 . In order to reduce the incidence of catheter-related bloodstream infections, it is desirable to reduce or eliminate the number of pathogenic organisms in this region. 
     Referring now to  FIG. 5A to 5C , various stages of installation of cap  20  are shown, wherein the insertion of the cap (with an elongate member) results in the flow of an anti-microbial containing liquid out the end of the catheter hub to kill microorganisms that would otherwise potentially intrude into the hub and then the catheter lumen. In  FIG. 5A , the cap  20  is shown immediately prior to being inserted into the hub  72  of a catheter  70 . Within the hub lumen  79  is a liquid locking solution  90 , the most proximal portion of which forms a meniscus  92 . The locking solution for hemodialysis catheters is most often heparinized saline (100 IU/ml to 5000 IU/ml of heparin), sodium citrate solution (typically 4% sodium citrate), or saline. Patient care technicians and nurses are trained to keep the meniscus  92  at the proximal end  74  of the hub  72 . However, it is not unusual for the meniscus to fall several millimeters within the hub lumen  79 . The antimicrobial agent must produce the desired effect in any of the standard lock solutions. In practice, the clamp  84  remains closed (producing a pinch point  85 ) unless fluids are being transferred through the catheter  70 ; this is standard practice because it decreases the risk of introducing an air embolus into the patient&#39;s bloodstream through catheter  70 . 
     In reference to  FIG. 5B , the elongate member  33  is shown partially inserted into the hub lumen  79 . The elongate member  33  displaces lock solution  90 , which results in the meniscus  92  being pushed out of the lumen  90  and onto the end face  76  of the hub  70 . Eventually, as the cap  20  continues to be inserted, the meniscus  92  (and lock solution  79 ) will travel over the catheter threads  78 . 
     Next, referring to  FIG. 5C , the cap  20  is shown fully inserted into the catheter  70 . In this embodiment, the meniscus  92  travels beyond the void  94 , completely filling the void  94  with lock solution. The lock solution causes the antimicrobial agent to dissolve, resulting in a transfer of antimicrobial agent from one or more of the coated parts (the elongate member  33 , the male luer  31 , and cap threads  41 ) into the solution. In addition, insertion of the elongate member into the locking solution further causes a transfer of antimicrobial agent to the previously uncoated parts such as the wall defining the inner hub lumen  79  and extension lumen  82 , the female luer  75 , the end face  76 , and the catheter threads  78 . Within several hours the solution within the void  94  may dry. In this manner an antimicrobial coating becomes transferred to the catheter threads  78  and the end face  76 , resulting in an enhanced ability to kill any organisms on the catheter threads  78  and the end face  76 , even if the organisms contaminate the surfaces after the solution dries. In practice, the void is often times infiltrated with sweat that contains organisms. In this scenario the dried antimicrobial agent becomes hydrated by the sweat, killing organisms that may be present in the sweat. Furthermore, the catheter threads  78  and the end face  76  become replenished with antimicrobial agent every time a new cap  20  is inserted. In current practice, a new cap is used after every dialysis session. The ability of the cap  20  to replenish the antimicrobial agent on a catheter  70 , into a targeted location with a high risk of serving as a microorganism source, overcomes a significant shortcoming of antimicrobial coated catheters in which the antimicrobial agent wears off with use or is only applied to the interior of the catheter. A desirable amount of antimicrobial agent on the catheter threads  78  is 20 μg to 2 mg, alternatively 200 μg to 1.5 mg, and desirably 500 μg to 1.2 mg of chlorhexidine acetate. However, it will be understood that different levels can also be achieved with success. 
     The male luer  31  makes contact with the female luer  75  to create a fluid tight seal. These parts are typically manufactured in accordance with the International Organization for Standardization standard ISO 594-2:1998(E) in order to ensure proper sealing and intermateability. However, the junction between the male luer  31  and the female luer  75  is not fluid tight along the entire length of the interface. Some manufacturers of medical device hubs intentionally manufacture their female luers such that the male luer contacts the female luer near the male luer end face. This is done in order to reduce the risk of the splitting the hub. However, the unintended consequence is that proximal end of the luer interface allows for the potential infiltration of organisms. Once the organisms are present, they may be pushed further into hub lumen  79  by current caps (or other devices) the next time a cap (or other device) is inserted. Once the organisms are within the hub lumen (distal to the male luer) they can multiply, resulting in planktonic and sessile organisms, and eventually a biofilm. This problem can be countered by placing an antimicrobial agent along the male luer  31 . The antimicrobial agent kills organisms that may be or become present along the female luer  75  before the organisms have a chance to be pushed into the hub lumen  79  or further multiply. Even with these protective measures, there is still a possibility that some organisms can make it beyond the female luer  75 . To overcome that potential shortcoming, the preferred embodiment also contains antimicrobial on the elongate member  33 , which dissolves or elutes into the lock solution  90 , to kill organisms in the hub lumen. 
     The minimum amount of antimicrobial agent on elongate member  33  was determined through laboratory testing in which elongate members were placed into catheters under a variety of lock solutions and challenge organisms. The type of lock solution was varied among saline, heparinized-saline, 4% sodium citrate solution, and human serum. A variety of challenge organisms were used, such as  Candida albicans, Pseudomonas aeruginosa, Staphylococcus aureus , and  Escherichia coli . Testing performed by the inventors showed a dose response; the more chlorhexidine acetate contained on the elongate member  33 , the more organisms that are killed in the catheter  70 . 
     The maximum amount of antimicrobial agent that is placed on each of the cap&#39;s surfaces was developed by first reviewing how much antimicrobial is safe for the patient and then comparing that to how much antimicrobial agent the patient can potentially be exposed to by each of the cap&#39;s  20  surfaces that contain antimicrobial agent (elongate member  33 , male luer  31 , and cap threads  41 ). The amount of antimicrobial that is safe for the patient was determined by reviewing published information on levels (especially bloodstream levels) that are generally regarded as safe for patients. 
     Testing was conducted in order to derive how much antimicrobial agent the patient can potentially be exposed to from cap  20 . The testing was designed to determine the transfer efficiency of antimicrobial agent from each applicable component (elongate member  33 , male luer  31 , and cap threads  41 ) to the bloodstream. In order to determine the potential bloodstream level, consideration was given for potential patient exposure that could occur under a variety of conditions, including unusual use or misuse (such as injecting the lock solution into the patient&#39;s bloodstream instead of aspirating the solution). The potential patient exposure was determined for each component individually and for the entire cap  20 . 
     The minimum amount of antimicrobial agent on the elongate member  33  is the amount required to obtain an acceptable reduction (also referred to as kill) of infection causing organisms. The volume of solution that the antimicrobial agent dissolves into is important to understand because the more solution that is present, the more dilute the antimicrobial agent can become. The confined volume of lock solution  90  within the lumen is defined by the location of the meniscus  92 , the geometry of the hub lumen  79 , the geometry of the extension lumen  82 , and the location of the pinch point  85 . Since each of these items may vary, there is a considerable range of confined fluid volumes that is possible. After accounting for the design variations of existing hemodialysis catheters, it is evident that the preferred embodiment needs to produce a therapeutic concentration of antimicrobial agent within a 0.7 ml volume. In one embodiment, the amount of chlorhexidine acetate on the elongate member  33  is greater is 10 μg to 5 mg. In an alternative embodiment, the amount of chlorhexidine acetate is 100 μg to 2 gm. In yet another embodiment, the elongate member contains 250 μg to 550 μg. 
     These embodiments can produce broad spectrum kill of the target organisms, yet result in a low enough dose of chlorhexidine acetate that, even if all of the lock solution containing chlorhexidine acetate is injected directly into the bloodstream, it will result in a bloodstream level that remains at safe levels. 
     In reference to  FIG. 6 , a cap  20  is shown fully inserted into a catheter  70 . This embodiment contains an end seal  47 . The end seal  47  provides additional benefit by preventing organisms from entering the distal opening  44  thereby preventing the organisms from subsequently progressing through the void  94  where they could then contaminate the end face  76  and female luer  75 . Reducing the number of organisms that can enter distal opening  44  can further reduce the incidence of CRBSI. The end seal  47  can be made of an elastic material so it is capable of stretching over the catheter threads  78  while the cap  20  is being inserted, and it should also conform to the shape of the hub  72  so it creates an effective organism-blocking seal. The end seal  47  is preferably made of a durable material so it does not rip or tear. It should be thin and flexible enough so it is easy to insert. The end seal  44  allows fluid to escape as the cap  20  is being inserted onto the catheter  70 , yet acts as a barrier to substantially retain the lock solution that was pushed into the void  94  during insertion. In the preferred embodiment, this is accomplished by keeping the wall thin and flexible enough to allow the increased pressure to escape where the end seal  47  contacts the hub  72 . In an example embodiment, the end seal  47  is over molded onto the retaining ring  40 . A thermoplastic elastomer, such as Exxon Mobile&#39;s Santoprene, can be used. However, other materials, such as silicone, may be suitable. In an embodiment, the end seal  47  is in the range of 0.005 inch to 0.100 inch thick. In another embodiment, the end seal  47  is in the range of 0.010 inches to 0.040 inches thick. 
     The lock solution in void  94  also acts as a barrier to organism infiltration. It contains antimicrobial agent that has dissolved from the cap  20  surfaces (elongate member  33 , male luer  31 , and catheter threads  78 ). In a desired embodiment, the antimicrobial levels result in an antimicrobial concentration that is highly effectively at killing a broad spectrum of organisms. 
     In reference to  FIG. 7 , the cap  20  is shown fully in cross section inserted into a catheter  70 . This embodiment can contain a thread seal  48  that is impregnated with an antimicrobial agent in the same amount as (and in place of) the amount on the cap threads  41  of  FIG. 5C . The thread seal  48  provides additional benefit by preventing organisms from entering the distal opening  44  and, since the void  94  is now occupied with the thread seal  48 , it prevents organisms from progressing through the occupied void  94  where they would otherwise contaminate the end face  76  and female luer  75 . Reducing the number of organism that can enter distal opening  44  can further reduce the incidence of CRBSI. The thread seal  47 ′ is preferably made of an elastic foam material that is capable of conforming around the catheter threads  78  while the cap  20  is being inserted, and it should also conform to the shape of the hub  72  so it creates an effective organism-blocking seal. The most distal end of the thread seal  47 ′ often has a thin layer of closed polyurethane to help reduce evaporation of the solution. The thread seal  48  is desirably made of a durable material so it does not rip or tear. One aspect of the thread seal  48  is that it allows fluid to escape as the cap  20  is being inserted into the catheter  70 , yet it acts as a barrier to substantially retain the lock solution that was pushed into the filled void  94  during insertion. In the preferred embodiment, this is accomplished by manufacturing the thread seal  48  out of an open cell hydrophilic medical polyurethane foam and having a thin layer of solid polyurethane at the most distal end of the thread seal  47 ′. The distal end of the thread seal  47 ′ is desirably thin, such as 0.001 to 0.020 inch, and flexible enough to allow the increased pressure to escape where it contacts the hub  72 . The thread seal  48  and the antimicrobial agent incorporated therein also acts as a barrier to organism infiltration. It contains antimicrobial agent that has dissolved from the cap  20  surfaces (such as one or more of the elongate member  33 , male luer  31 , and thread shield  48 ). 
       FIG. 8A  refers to an alternative embodiment of the cap  20  which possesses a novel tip  34 ′ that has a diameter that is smaller than the diameter of the hub lumen  79  when the tip  34 ′ is inserted into a catheter  70 , but subsequently expands in size. This embodiment is especially beneficial when the cap  20  is used in a catheter  70  that does not have a clamp for confining the solution, or in cases where it is desirable to further limit the amount of antimicrobial agent required (less is required because the volume of confined solution is lower). The tip  34 ′ is shown in  FIG. 8A  in its unswollen state during insertion in order to allow the elongate member to be easily inserted and to minimize its potential for pushing organisms distal to the tip  34 ′ by a plowing action. The elongate member in a preferred embodiment remains sufficiently stiff while it is being inserted onto into the catheter  70  and it does not require any extra parts or aids for insertion. 
       FIG. 8B  refers to an alternative embodiment of the cap  20  as described in reference to  FIG. 8A , except the tip  34 ″ is shown in its swollen state. In the depicted embodiment the diameter of the tip  34 ″ is equal to the diameter of the hub lumen  79  in its swollen state; the tip  34 ″ preferably conforms to the surface of the hub lumen  79  as it swells. The swollen tip  34 ″ is beneficial for confining the solution, or in cases where it is desirable to further limit the amount of antimicrobial agent required (less is required because the volume of confined solution is lower). The tip  34 ″ is removable from the hub lumen  79  when reasonable removal force is applied to the cap  20 . This is achieved by choosing the material and size the tip  34 ″ such that, when it is in its swollen state, the normal force that the tip  34 ″ applies to the wall of the hub lumen  79  is sufficiently low to allow acceptable removal force. In an example embodiment the diameter of the unswollen tip  34 ′ (reference  FIG. 8A ) is 0.060 inches, the diameter of the confined swollen tip  34 ″ is 0.098 inches (the same diameter as the hub lumen  79 ), and the diameter of the unconfined swollen tip is 0.110 inches when placed in normal saline. However, these diameters will vary to match the diameter of the device that the cap is being used with. The preferred unconfined swollen diameter (defined as the diameter the tip will expand to if it is not confined by a lumen wall) is slightly larger than the diameter of the hub lumen  79 . An additional beneficial effect of the swollen tip is that it produces a scrubbing effect on the catheter wall that will physically remove organisms adhered to the interior wall section upon removing the cap from the catheter. 
     In one embodiment, the tip is manufactured to produce anisotropic swelling, such that the diameter increases but the length does not substantially increase. In another embodiment the entire elongate member is made of an anisotropically swelling material such that the diameter increases but the length does not substantially increase. 
     In one implementation, the material of the tip  34 ″ consists of a swellable polyurethane, such as Lubrizol TG-500, that has been heat fused onto the elongate member  33  which is a non-swell able polyurethane, such as Lubrizol 1065D. These materials provide acceptable swelling, durability, strength and flexibility. The elongate member is coated with antimicrobial agent in an amount sufficient to obtain an adequate antimicrobial effect, yet low enough to remain safe for the patient. 
     In reference to  FIG. 9 , this alternative embodiment of the invention is useful in applications where an elongate member will not fit into a catheter because the internal diameter of the catheter is too small, such as with peripherally inserted central catheters (PICC). In this embodiment, the cap  20  does not contain an elongate member as in previous embodiments. Instead, the cap has a luer end face  38  that is flat or slightly recessed, and the end face  38  is coated with an antimicrobial layer  39 . The preferred type and amount of antimicrobial in the antimicrobial layer  39  is the same as the elongate member (reference the description for  FIG. 5C ). Similarly, the male luer  31  and the catheter threads  78  preferably contain the same type and amount of antimicrobial agent as the other embodiments. The antimicrobial agent is preferably applied to the end face using a precision metering pump with 15% chlorhexidine acetate in a methanol solution. Other solvent, percentages and coating methods may be used. 
     In reference to  FIG. 10A , an alternative embodiment of the invention is shown in which the cap  20 ′″ is manufactured from two components, a retaining ring  40 ′″ and an insert  30 . It is desirable to have a highly controlled and repeatable amount of antimicrobial agent placed upon the desired regions of the cap  20 ′″. Itis also preferred to have different amounts of antimicrobial on the different regions. It becomes easier to coat each region of the cap  20 ′″ if the retaining ring  40 ′″ is not blocking access to the male luer  31  (and vice versa). This is accomplished by manufacturing the cap  20 ′″ as two separate pieces, the retaining ring  40 ′″ and the insert  30 . The preferred amount of antimicrobial agent within each region remains the same as presented above (refer to Ref. SC). 
     In reference to  FIG. 10B , the insert  30  is coated with chlorhexidine acetate the elongate member  33  and along the male luer  31 . The plate  32 , cap shoulder  36 , and the retaining flange  37  do not require coating. The two parts that are coated are the male luer  31  and the elongate member  33 ; contain the same amount of antimicrobial as referenced above. 
     In reference to  FIG. 10C , the plate  32  at the proximal end of the insert  30  has a hole  35 . The purpose of this hole  35  is to improve manufacturing. For instance, the hole  35  creates a convenient feature that can be used for holding and rotating the insert  30  to allow the part to be spun as it is being coated. The hole  35  also reduces shrinkage in the injected molded insert  30  by creating more uniform wall thickness. 
     In reference to  FIG. 10D , the retaining ring  40 ′″ is a commercially available product from Value Plastics, Inc. with the exception that the cap threads  41  are coated with an antimicrobial agent. The antimicrobial agent in the preferred embodiment is chlorhexidine acetate in the same preferred amount as disclosed above. The retaining ring  40 ′″ is readily coated using a spraying technique where the retaining ring  40 ′″ is spun along its axis, and the antimicrobial is sprayed directly onto the cap threads. As an alternative coating method, the cap threads  41  were coated by filling the internal portion of the ring  40 ′″ with 7% chlorhexidine methanol solution, subsequently draining the solution and allowing the parts to dry. This resulted in approximately 1.2 mg of chlorhexidine acetate on the cap threads  41 . The dose of antimicrobial may be adjusted by adjusting the solution concentration. 
     In reference to  FIG. 10E , the retaining shoulder  46  comes into contact with the insert (not shown) when the insert is inserted inside the retaining ring  40 ′″. The proximal opening  43  is used to initially receive the insert  30  (refer to  FIG. 10F ) during assembly. The retaining fingers  45  are designed to retain the retaining ring  40 ′″ onto the insert, as will be described in the reference below. The ring shoulder  46  helps secure the insert. 
     In reference to  FIG. 10F , the preferred embodiment for the two-piece cap  20 ′″ is shown. The insert  30  is shown fully inserted into the retaining ring  40 ′″. The tip  34  was pushed through the proximal opening until retaining ring  40 ′″ bottomed out on the plate  32 . The retaining fingers  45  are engaged with the retaining flange  37  to secure the retaining ring  40 ′″ on the insert  30 . 
     It is desirable to have the retaining ring  40 ′″ not rotate freely on the insert  30 . Instead, it is preferred to have the torque be greater than 0 pound-inches (lb-in) but less than 2.0 lb-in. In a more preferred embodiment, the torque is between 0.1 lb-in and 1.25 lb-in. In the most preferred embodiment, the torque is between 0.2 lb-in and 0.5 lb-in. By controlling the diameter of the insert shoulder  36  such that it interferes with ring shoulder  46 , the torque can be controlled as shown in the graph depicted in  FIG. 11 . 
     It is preferred to keep the interference between the ring shoulder  46  and the insert shoulder  36  within the range of 0.002 inch and 0.009 inch in order to keep the rotation torque within an acceptable range. 
     Antimicrobial Agent 
     An antimicrobial agent can be incorporated both into the elongate member material and/or on the elongate member surface of the present invention. In a preferred embodiment, the antimicrobial agent is chlorhexidine acetate; approximately 250 μg of chlorhexidine acetate is coated onto a 17 mm long×1.9 mm diameter rod-shaped elongate member, resulting in a chlorhexidine acetate layer approximately 2 μm thick along. The luer portion is coated with 50 μg of chlorhexidine acetate, resulting in a layer that is approximately 0.4 μm thick. It is also possible to inject an antimicrobial agent into the catheter using a syringe, or to deliver antimicrobial agents by way of the connector tip cavity (dry dissolvable amount, applicable for Citrate or others requiring large amounts of antimicrobial agent). 
     The elongate member has the added benefit of displacing fluid from within the catheter as it is inserted, transferring the solution to the outer proximal region of the catheter connector (end face and treads). Antimicrobial agent from the cap dissolves into the displaced fluid, and thereby disinfecting the proximal end of the connector. Furthermore, when the fluid dries, it deposits a coating of chlorhexidine acetate or other appropriate antimicrobial on the connector as described above. As an alternative to using the elongate member, is the chlorhexidine acetate or other antimicrobial agent may be delivered by a coating on a luer tip (such as 250 μg of chlorhexidine acetate in a layer that is approximately 20 μm thick). 
     An antimicrobial composition is located on the outer surface of the elongate member, the male luer connector, and the retaining ring The antimicrobial composition elutes from the elongate member after insertion of the elongate member/rod into a catheter. When the system is inserted into the catheter, the antimicrobial agent dissolves into the fluid contained within the catheter, thus coming into contact with infectious organisms that might be present along the connector surfaces and lumen wall of the catheter or in solution. Additionally, the antimicrobial agent and any infectious organisms are confined together in the small space along within the catheter. Another benefit is that the confining action of the clamp traps any infectious microbes within the catheter and prevents them from being transmitted to other areas of the catheter or to the body to prevent a systemic infection. 
     The antimicrobial agents should kill and/or provide stasis of Gram-positive and Gram-negative bacteria and fungi. The agents may also have efficacy at killing organisms within an established biofilm and/or degrading the extracellular matrix of the film. However, this is not necessary for the invention to be beneficial because the invention is designed to kill organisms before they have an opportunity to form a biofilm. The preferred antimicrobial agent is chlorhexidine acetate, also known as chlorhexidine diacetate. Other compounds containing chlorhexidine may be used (such as chlorhexidine free base, chlorhexidine gluconate and chlorhexidine with dyes). Chlorhexidine acetate has an advantage over chlorhexidine gluconate because the risks associated with para chloroaniline may be minimized. Other suitable antimicrobial agents may also be used. In general, the preferred antimicrobials are soluble in water, they have a history of clinical use with a demonstrated safety profile, they are antibiotic-free, they can be applied onto a medical device, and they can be subsequently dissolved into a composition having an effective concentration to inhibit growth of bacterial and fungal organisms. Suitable materials include tetrasodium ethylenediaminetetraacetic acid (tetrasodium EDTA), sodium citrate (yielding a concentration of 30% or higher), iodine, taurolidine, disodium EDTA, silver compounds (including silver nanoparticles and ions), silver sulfadiazine, and, triclosan. 
     While one particular drug or antimicrobial agent may provide relief from a wide range of challenging organisms that could potentially lead to catheter-related bloodstream infection, two or more agents may be used to increase efficacy against a broad range of infectious organisms (bacteria and fungi). 
     In particular, catheter-related infections arise from three broad classes of organisms: fungi, Gram-negative bacteria, and Gram-positive bacteria. If an antimicrobial agent can be identified that would abate one or two of these types of organisms, while this would certainly be beneficial, it would leave the patient vulnerable to the remaining type(s). By pairing agents with different modes of action, infections by an increased spectrum of organisms can be prevented. This synergy would likely lead to further decreases in catheter-related morbidity and mortality, lessening the impact of the implanted catheter on the patient&#39;s quality of life. The preferred combinations of antimicrobial agents are chlorhexidine acetate and EDTA, silver sulfadiazine and sodium dodecyl sulfate, and silver sulfadiazine and methylene blue. 
     Although treating, preventing, and eliminating infectious organisms for the prevention of infections is the primary use of the cap, ancillary benefits can also be envisioned which would involve incorporating additional agents. An antithrombotic agent eluting from the elongate member can be used to improve the action of the heparin used currently in the locking solution. An enzyme or agent which promoted degradation of the extra-cellular matrix of biofilm (generally composed of polysaccharides) could enable use of the cap for treatment as well as prevention. 
     In principle, antibiotics (rifampin, minocycline, etc.) can be incorporated into the cap or similar device and be as effective as non-antibiotic antimicrobials. However, continuous exposure to one antibiotic can lead to antibiotic resistant bacteria strains, for example, methicillin resistant  S. aureus  (MRSA). Therefore, the preferred embodiment uses an antimicrobial agent selected from the subset of those which are not antibiotics. If, for some reason, an antibiotic is used, the risk of developing antibiotic resistant strains of bacteria may be mitigated by preparing a second, complimentary, cap containing a different antibiotic. By using the two caps in an alternating fashion with successive dialysis treatments, infectious organisms that are resistant to one antibiotic may be killed by the other. 
     Experiments have been conducted to examine the performance of the preferred embodiment of the invention, which is called “Pursuit Vascular&#39;s ClearGuard HD” or the “ClearGuard HD”. These experiments demonstrate that the ClearGuard HD is effective at substantially reducing organisms within catheters as intended. Two of the experiments are highlighted below. 
     In an experiment conducted at Pursuit Vascular, coated caps were effective at consistently transferring more than 50 μg of chlorhexidine acetate (also referred to as chlorhexidine diacetate) onto the catheter&#39;s threads with a single connection. Such transfer provides the catheter with a means of further reducing infection-causing organisms which is replenished with every use of the invention. IO μg or more of chlorhexidine is effective at reducing bacteria and other infection-causing organisms at the threads, and further preventing the organisms from infiltrating the catheter&#39;s connector end face, luer and lumen. Chlorhexidine acetate has a wide safety profile when used outside the catheter where there is little risk of it entering the bloodstream. A preferred range of chlorhexidine on the cap threads is 100 μg to 2500 μg. 500 μg to 1200 μg is more preferred. 
     For instance, if using a chlorhexidine based antimicrobial, approximately 50 μg of chlorhexidine acetate can be effective in some embodiments. This was demonstrated in an experiment conducted at Pursuit Vascular in which 50 μg of chlorhexidine was coated on the cap&#39;s luer portion. The caps containing the coated luers killed all of the  Candida albicans  that were seeded within the catheter&#39;s luer region. Within the same experiment, the  Candida albicans  remained viable when uncoated caps were used. Greater than 5 μg chlorhexidine acetate on the luer region is effective; 10 μg to 300 μg is preferred, and 30 μg to 80 μg is most preferred. 
     Laboratory testing conducted for Pursuit Vascular, Inc. demonstrated that 250 μg of chlorhexidine acetate on the elongate member produces greater than a 10,000× reduction in number of infection-causing organisms when the cap is used in a standard hemodialysis catheters containing saline, heparin-saline, or saline with 4% sodium citrate. The safety profile of the invention can be enhanced by limiting the amount of chlorhexidine acetate available to enter the bloodstream, the preferred maximum amount of chlorhexidine acetate on the elongate member is 2000 μg, more preferred is 1000 μg, and most preferred is 350 μg. 
     Experiment 1: 
     The objective of this experiment was to assess the antimicrobial effectiveness of Pursuit Vascular&#39;s ClearGuard HD device in the most difficult clinically-relevant model. Since the ClearGuard HD is intended to be placed in catheter hubs, but not extend into the extension tubing, the catheter model was chosen to be a female luer connector, extension tube and clamp. The total length of the female luer connector and the extension tubing was manufactured to maximize the length and volume that would be expected to be encountered clinically.  Candida albicans  (fungus) was chosen as the challenge microorganism, because in previous tests  Candida albicans  was shown to be the most challenging microorganism for the ClearGuard HD to eradicate.  Candida albicans  were added to three different lock solutions: heparin-serum, saline-serum, and SDB broth. These solutions represent the most relevant (and challenging) solutions that would be expected clinically. The catheters were filled with the lock solutions and  Candida albicans , next the caps (either the ClearGuard HD or a standard cap) were secured, and then the catheters were incubated for approximately 46 hours to simulate the time between dialysis sessions. After incubation, the caps were removed and the lock solution was tested for the presence of organisms. 
     Experiment 1 results: The organism count is shown in  FIG. 11  for ClearGuard HD caps and standard caps (shown as “with CGHD” and “without CGHD”, respectively). 
     
       
         
           
               
            
               
                   
               
               
                 Organism Count at Study End 
               
            
           
           
               
               
               
               
            
               
                   
                 With 
                 Without 
                 Organism 
               
               
                 Solution 
                 CGHD 
                 CGHD 
                 Reduction* 
               
               
                   
               
               
                 5000 IU/ml Hep-Saline 
                 0.0E+00 
                 3.6E+06 
                 3.6E+06 
               
               
                 with 25% Serum 
               
               
                 Saline with 25% Serum 
                 0.0E+00 
                 3.8E+03 
                 3.8E+03 
               
               
                 SDB Broth 
                 0.0E+00 
                 7.7E+08 
                 7.7E+08 
               
               
                   
               
               
                 *Actual reduction in organism count is likely higher than calculated in this test because no organisms survived in the CGHD arm of the study. 
               
            
           
         
       
     
     The antimicrobial effectiveness of the ClearGuard HD was assessed against  Candida albicans , the microorganism which has been the most difficult to eradicate when tested in a clinically relevant catheter model containing the most challenging and clinically relevant fluids. 
     All test samples using the ClearGuard HD had complete kill of the  Candida albicans . In comparison, all control samples demonstrated growth of the CA. Since no  Candida albicans  survived during the ClearGuard HD portion of the test, the actual  Candida albicans  reduction may be significantly higher (better) than the sensitivity of this test. The minimum reduction of  Candida albicans , when using the ClearGuard HD in place of a standard cap, was shown to be: 
     a. 3.6×10 6  CFU/ml for Heparin with 25% Serum 
     b. 3.8×10 3  CFU/ml for Saline with 25% Serum 
     c. 7.7×10 8  CFU/ml for SDB Broth 
     This test demonstrates that the ClearGuard HD produces a significant reduction in  Candida albicans  within a clinically relevant catheter and with clinically solutions.  Candida albicans  was previously shown to be the most difficult organism to reduce of the other clinically relevant microorganisms tested, therefore concluding that the ClearGuard HD produces broad-spectrum reduction in clinically relevant microorganisms. 
     Experiment 2 
     The objective of this experiment was to assess the relative rate of microorganism contamination in hemodialysis catheter lumens when using the ClearGuard HD versus standard caps in a simulated clinical environment. This experiment was intended to examine the effectiveness of the ClearGuard HD at preventing microorganism contamination of hemodialysis catheter lumens (both proximal and distal to the extension tubing clamp), compared to standard caps in a simulated clinical environment. Growth media was used inside of the catheter instead of the standard locking solution in order to provide an extremely sensitive means of detecting whether any microorganisms entered inside the catheter. 
     The primary route for infections-causing microorganisms to enter and colonize a hemodialysis (HD) catheter is generally accepted to be through the catheter&#39;s hub. During clinical use, hemodialysis catheter hubs are routinely exposed to microorganisms because the catheter and hub lies against the patient&#39;s skin. All commercially available catheter caps are primarily designed to keep fluid inside the catheter lumen but they are not well designed for preventing microorganisms from reaching and colonizing catheter lumens. 
     In order to compare whether the rate of microorganism colonization is affected by cap type (ClearGuard HD versus standard cap), twenty identical catheters were affixed to clothing, in a manner that would keep the catheters in contact with human skin, which occurs during clinical use. The catheters were kept in contact with the skin for a maximum of 26 days. Once a catheter&#39;s lumen was determined to be contaminated, the catheter was allowed to be removed from the study. The test consisted of two arms: 1) the ClearGuard HD arm, and 2) the standard cap arm. Except for the cap type used, the two arms were identical in all other ways (i.e., identical catheters, solutions, handling, etc.). 
     The study was designed to mimic the hemodialysis clinical practice as closely as practical. The entire volume of lock solution, including the solution distal to the clamp, was included in the microbiological testing to ensure with high probability that if any microorganisms were present anywhere within the catheter that they would be detected. Standard microbiological techniques were used to test for the presence of organisms. 
     The number of catheters that remained free from microorganism contamination as time progressed is illustrated in  FIG. 13  below. Within fourteen days, all catheters using standard caps had become contaminated, while none of the catheters using the ClearGuard HD had become contaminated throughout the full twenty-six days of the experiment. 
     This experiment showed that, when catheters were filled with a growth media, were worn to simulate actual patient end use and were subjected to a standard dialysis fluid exchange schedule, the catheters using standard caps became contaminated with microorganisms at a mean time to failure of 8.9 days, and all of these catheters (10 out of 10) became contaminated by 14 days. In comparison, none of the catheters using the ClearGuard HD (0 out of 10) became contaminated throughout the entire 26 day test. The ClearGuard HD performs significantly better than standard caps (the current standard of care) at reducing microorganism contamination inside of catheters in a simulated clinical environment. While the invention has been particularly shown and described as referenced to the embodiments thereof, those skilled in the art will understand that the foregoing and other changes in form and detail may be made therein without departing from the spirit and scope of the invention.