This application claims the benefit of priority under 35 U.S.C. 119 to European Application No. 15154328,7, filed on Feb. 9, 2015, which application is incorporated herein by reference in its entirety.
The present invention relates to a container for an implant, characterized in that the inner shape and/or dimensions of the container are adapted to mirror the outer shape and/or dimensions of the implant. The invention further provides the use of the container in methods for infection control and in methods for the diagnosis of infections of implants. These methods comprise an elution step of the microorganisms from an explanted implant, which is performed by ultrasonic methods using the entire container of the invention with the implant inside. Advantageously, the necessary volume of the solution for eluting the microorganisms form the surface of the implants can be reduced by up to 90% due to the construction of the inside of the container. It will additionally enable a transport between the operating room (OR) and the lab without contamination risk.
Infections of implants may occur during the implantation of a prosthesis, such as artificial joints and the like, into a subject, accompanied by long-lasting discomfort and chronic ailment after implantation. State of the art methods for the detection of pathogenic microorganisms directly from the joint include the aspiration of synovial fluid, a smear-test of the joint and of the surface of the prosthesis as well as the collection of periprosthetic tissue. According to currently valid standard methods for the diagnosis of prosthesis infections, only the detection of at least two identical pathogens from a joint was proving an infection. Therefore, in order to prove an infection always 3 to 6 tissue samples should be collected and analysed (see Berbari E F et al.: Risk factors for prosthetic joint infection: case-control study. Clin Infect Dis 1998; 27: 1247-1254). One goal of this procedure is to ensure that cross-contaminations, e.g. during explantation and handling the explanted prosthesis by the operating room (OR) staff, can be excluded. However, the aforementioned methods have originally not been developed for the diagnosis of prosthesis infections. Moreover, the sensitivity and specificity of these methods is unsatisfactory, because the associated microorganisms correspond to the normal flora of the skin, and thus a contamination of the sample cannot be excluded entirely. Another disadvantage of the aforementioned prior art methods is that only the tissue and the fluid surrounding an implant is analysed, but not the implant itself. However, in the adjacent tissue there can often not be found a substantial number of pathogens. Thus, the main goal of the present invention is to improve the sensitivity of the methods for diagnosing prosthetic infections, in particular to improve the identifiability of pathogenic microorganisms.
A prosthesis infection is usually caused by microorganisms that are attached to the surface of the implant itself, where the microorganisms form an extracellular matrix, the so-called biofilm. A biofilm facilitates the survival of the microorganisms, because the activity of the individual pathogens is decreased significantly. The presence of the bacteria within biofilm may make them reluctant to grow and inaccessible to antibiotic treatment. Microbial biofilms growing adherently on prosthetic surfaces may prevent the detection of the pathogens causing prosthetic joint infections. Bacteria contained in biofilms show an up to 1000-fold higher resistance to growth-dependent antimicrobial substances. This is confirmed by the fact that the minimum inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) in the biofilm is several times higher than for the free-living form of these microorganisms. There are estimates that biofilm-forming bacteria are responsible for about 60% of all nosocomial infections and false-negative smear-tests obtained from wounds.
Thus, disrupting the biofilm from the prosthetic surface to release the pathogens into a test solution may improve the results of the diagnostic methods and thereby contribute to the treatment of the infection. To overcome the disadvantages of the conventional culture methods of periprosthetic tissue and/or fluid for the diagnosis of periprosthetic-joint infections, Trampuz et al. (Trampuz et al. 2007. Sonication of removed hip and knee prosthesis for diagnosis of infection. N Engl J Med 357:654-663) applied long-wave ultrasound to explanted prostheses in order to disrupt the biofilms and to enhance bacterial growth in subsequent microbiological analysis methods. Trampuz et al. reported that ultra-sound sonication before cultivation of explanted hip and knee prosthesis to dislodge adherent bacteria yielded a significant better recovery of bacterial growth and culture than the conventional methods using periprosthetic tissue and/or fluid.
Typically, when using an ultra sound method, the explanted prosthesis or components thereof are placed in a sterile container and covered with 400 ml or more of sterile Ringer's solution. This method has the disadvantage, that a high volume of the solution for the eluation of the microorganisms from the surface of the implant must be used. This is particularly disadvantageous for low grade infections which cannot be detected within these high volumes of the solution.
In another attempt, the explanted prostheses where placed into liquid-filled sterile plastic bags. However, through ultra-sound sonication, small holes occurred in the walls of the bags resulting an increased cross-contaminations accompanied by a false-high sensitivity and decreased specificity of the method.
Overview
It was the purpose of the invention to overcome the disadvantages of the prior art methods. In particular, it was the purpose of the invention to provide a device for diagnosing microbial infections of implants with high sensitivity and specificity, but a highly reduced risk of cross-contaminations.
This problem is solved by the provision of a container for an implant, wherein the inner shape and/or dimensions of the container are adapted to the outer shape and/or dimensions of the implant.
The container of the invention has the advantage, that the volume of the solution necessary for the destruction of the biofilm on the surface of the explanted implant and the elution of the microorganisms from the implant using ultra-sound sonication methods can be reduced drastically, e. g. from about 100-400 ml to 10-50 ml. In a preferred embodiment, the volume of said elution solution can be reduced by 50%, 60%, more preferably by 70% or 80%, most preferably by 90% or more.
In general, the inner volume of the container of the invention is slightly larger than the volume of the explanted implant. Preferably, the inner volume of the container is 50% or 40% larger than the volume of the implant, more preferably 30% or 20% larger than the volume of the implant, Most preferably, the inner volume of the container is larger only minimally, e. g. 10%, than the volume of the implant, and furthermore, the shape and/or dimensions of the inside of the container correspond to the outer shape and/or dimensions of the explanted implant, which is to be analysed for infections.
This embodiment has the advantage, that the container of the invention, when containing an explanted implant, must be filled with a minimum volume of an elution solution only. Moreover, it is possible to concentrate eluted microorganisms, including pathogenic bacteria, in a minimum volume of the elution solution. Thereby, an increase of the number of colony forming units (CFU) per ml elution solution can be reached, which in turn leads to a lower detection limit for the identification of specific microorganisms. In particular, local infections can now be detected with a much higher probability, in contrast to the conventional methods of the prior art, especially those, which are presently based on the use of ultra-sound.
Suitably, the container of the invention comprises a lid at the proximal end. In a preferred embodiment, such a lid is directly connected to the container via a connection means, and the lid and the container are made from one piece. The lid has the function that the container can be closed tightly and that the inner space of the container can be maintained sterile before an explanted implant is inserted into the container. After insertion of the explanted implant, the lid is especially suitable to close the container tightly in order to prevent any cross-contaminations entering from outside into the container.
In general, any types of lids are possible for use to seal the container. In a preferred embodiment, the lid of the container contains a means, e. g. a clip or else, to fix the implant inside the container after the lid is closed. This embodiment has the advantage that the implant inside the container is tightly fixed during performing the sonication method in the ultra-sound bath. Thereby, damages of the wall of the container due to a possibly moving implant inside the container during sonication in the ultra-sound bath can be prevented. This in turn reduces the risk of the occurrence of leakages in the container wall. In contrast to devices used in prior art methods, such as plastic bags, it is possible with the container of the invention to minimise, more preferably to exclude, the penetration of cross-contaminations through damages of the container body during sonication in the ultra-sound bath.
Moreover, due to the prevention of possible damages of the container during sonication in the ultra-sound bath, the safety of the OR staff and/or laboratory staff, who are handling the container of the invention, can be dearly improved compared to the means used in the prior art so far.
In a further embodiment, the container of the invention comprises an injection hole for the injection of the elution solution into the container after the explanted implant has been inserted into the container and after the lid of the container has been sealed. Such an injection hole can be comprised in the container body itself or, more preferably, can form a part of the lid.
Any injection holes known from the prior art, which are suitable for methods performed under sterile conditions, are suitable for use with the container of the invention. Preferred are injection holes, which enable the administration of the elution solution to the inside of the container under sterile conditions. Suitably, the injection hole is sealed with a membrane, such as a rubber membrane or silicone membrane, which allows the application of the elution solution to the inside of the container with a syringe under sterile conditions.
In a preferred embodiment, the space between the explanted implant inserted into the container of the invention may be completely filled with an elution solution under sterile conditions. If the lid is sealed to the container and a syringe is used to administer the elution solution, the air contained in the sealed container will be replaced by the elution solution, i.e. the air contained in the sealed container must have the possibility to escape. This problem can he easily solved by placing the needle of a syringe in the membrane of the injections hole. Suitably, such a needle may be connected to a sterile filter or bacterial filter in order to allow the replaced air to escape from the container during administration of the elution solution without contaminating the lab environment with bacteria from the implant. Such bacterial filters are conventional and available in the art.
The container of the invention including the lid can be made of any suitable construction material, which allows either a sterile production of the container or the sterilisation of the container after the production. Accordingly, the container of the invention can be made of metal, glass or plastics or combinations thereof.
More preferably, the container of the invention is made of a plastics. Suitable plastics for producing the container of the invention are selected from those, which allow an easy and cheap manufacturing of the container on the one hand, but on the other hand are approved for the use in medicine or food industry and sustain ultrasonic treatment w/o weakening, i.e. w/o loss of stability.
Such plastics are suitably selected from thermo-formable plastics or plastics capable of injection moulding. Furthermore, the plastics used must not release substances, which are toxic for bacteria in order to prevent false-negative analysis results in the diagnostic methods of the invention.
Suitable plastics for use in the manufacturing of the container of the invention by injection moulding are for example selected from polyolefins such as polypropylene, acrylic glass, also known as plexiglass ((poly(methyl methacrylate), PMMA) for a transparent appearance, polystyrene (PS) and its copolymers (ABS=acrylonitrile-butadiene-styrene), polyamide (PA) and polyoxymethylene (POM).
In a preferred embodiment, the container of the invention is made of polypropylene.
Suitable thermo-formable plastics are any thermoplastics, e. g. those selected from polyvinylchloride (PVC), polyethyleneterephthalate (PET), polystyrole (PS) and polyolefins, such as polypropylene, but also acrylnitrile-butadiene-styrole (ABS) or polyaryletherketone (PAEK) such as polyether ether ketone (PEEK).
In a further preferred embodiment, the container of the invention is made of polypropylene without addition of deforming supporting agents, plasticizers and biocides.
Generally, conventional methods known to the person skilled in the art, such as injection moulding or thermo-forming, are used to manufacture the container of the invention. Accordingly, the container of the invention is easily and cheap to produce.
In yet a further embodiment, the container of the invention may be re-used several times. In such cases, the container must be sterilized after each use. However, in order to increase the safety of the OR and lab staff when handling the container of the invention, a one-time-use of the container is intended. Most preferably, the container of the invention is used as a disposable.
It is possible, to produce a container of the invention, which is specifically adapted to any kind of implant. In other words, it is possible with the conventional production methods known in the art, to produce a container of the invention wherein at least the inner shape and/or dimensions of the container are adapted to the outer shape and/or dimensions of an implant selected from the group consisting of knee prostheses, hip prostheses, shoulder prostheses and the like.
In a further embodiment, the invention provides the use of the container of the invention in methods for infection control and/or diagnosis of infections of implants. These methods allow the handling of an explanted implant wider sterile conditions. Cross-contaminations of the explanted implants can be minimized. There is a safe transport of the implant from the operating room (OR) to the laboratory, where the microbiological investigations are performed, possible. As described above, the use of the container of the invention in particular gains more precise results in the concentration-dependent analysis of infections of implants by limiting the volume of the elution solution.
The container of the invention can be used for quality control (QC) purposes and is also suitable to provide an easy way to dissolve bacteria adhered to an implant surface. The latter is of interest for septic revision surgery because the treatment regime depends on the specific strain identified. Therefore, the bacteria have to be detached from the implant and to be cultured using microbiological standard tests. The use of an ultrasonic bath can even improve the results. Nevertheless, accuracy is limited to the concentration as mentioned above.
Thus, in a further embodiment, the invention provides a method for controlling the infection of implants, such as prostheses or prosthetic components. Such method usually comprises in a first step the explanting of the prosthesis or prosthetic component. Thereafter, said prosthesis or prosthetic component is inserted into the container of the invention and the lid of the container is sealed tightly in order to prevent cross-contaminations of the explanted implant in the container, but also in order to prevent contaminations of the OR staff and the lab staff. The method further comprises the step of adding a sterile elution solution to the remaining space or volume between the inside of the container and the prosthesis or prosthetic component comprised in the container. Suitably, the sterile elution solution is inserted into the container under sterile conditions, for example using a syringe. This step can also be performed directly in the OR. Alternatively, the step of addition of the elution solution can also be performed later in the microbiology lab.
Preferably, the elution solution used in this method is a solution, which is not harmful for the microorganisms detached from the surface of the implant. A suitable elution solution may be selected from a buffer solution, an isotonic solution, culturing broth or else. More preferably, Ringer's solution, which is isotonic with blood, is used as elution solution in the container of the invention.
Thereafter, the container of the invention containing the prosthesis or prosthetic component and the elution solution inside, is placed into an ultrasonic bath and sonicated for a desired time. After sonication, aliquot samples can be taken from the container under sterile conditions. Thereby, it is not necessary to open the container. The samples can be taken from the container via the same way, e. g. by using a sterile syringe, as was used to add the elution solution. Again, this possibility to obtain samples from the elution solution without opening the container minimizes the risk for cross-contaminations of the samples on the one hand, and of the laboratory personal on the other hand.
The aliquot samples taken from the elution solution in the container of the invention may then be analysed for microbial infections, using any available conventional methods, such as plating the samples on different agar plates, e.g. aerobic and anaerobic sheep-blood agar plates, and calculating the number of colony forming units (CFU) after cultivation.
By using the container of the invention in the methods for controlling an infection of an implant and/or for the diagnosing of an infection of an implant, it is possible to reduce the necessary volume of the elution solution to a minimum volume. The sonication step leads to the decomposition of the biofilms that are established on the surface of said prostheses or prosthetic components, and further to the elution of the microorganisms from the surface of the prostheses or prosthetic components. Due to the minimum volume of the elution solution used, the eluted microorganisms are concentrated in the elution solution of the container of the invention rather than they are diluted in this solution as it is known from the devices presently used in the prior art.
In a preferred embodiment, the invention provides a method for controlling the infection of prostheses or prosthetic components comprising the steps of
The volume of the aliquot samples taken from the container after sonication can vary, dependent on the type of microbiological analysis or test, which is performed subsequently. Usually, the volume of the aliquot samples is between 0.05 and 0.5 ml. Typically, the volume of the aliquot samples is 0.1 ml or 0.5 ml.
In a further embodiment, the method for controlling the infection of an implant, such as prostheses or prosthetic components, can also be performed with implants that are already removed from the body of the subject, i. e. which are already explanted.
Accordingly, the present invention further provides a method for controlling the infection of an already explanted prosthesis or prosthetic component, comprising the steps of
The method of the diagnosis of microbiological infections of an implant in a subject according to the invention is further suitable for the identification of specific bacteria.
Besides the aforementioned conventional methods for the identification of microorganisms, in particular bacteria, more particular pathogenic bacteria, it is also possible to use other methods for the identification of bacteria. Such methods may be selected from polymerase chain reaction (PCR), IR spectroscopy, microarray based bacteria identification and the like. The aforementioned methods for controlling the infection of implants, such as prostheses or prosthetic components, may thus further comprise a step of identifying and distinguishing bacterial strains using PCR, IR spectroscopy or microarrays.
The most common pathogens in prosthesis and implant infections are Staphylococcus aureus, Staphylococcus epidermidis and other Staphylococcus spp., Corynebacterium spp., Streptococcus spp., Enterococcus spp., Propionibacterium spp., etc.
The colony count of these pathogens in samples, when taken from periprosthetic tissue, is often so low that these bacteria cannot be detected within these samples. The same holds true for the ultrasound methods presently used in the prior art, where a very high volume of elution solution is used. Only with the container and methods of the present invention, wherein a minimum volume of the elution solution is used during ultra-sound sonication, it is possible to detect and diagnose low-grade infections of said pathogens with high accuracy and reliability. The container of the invention and the methods of the invention using said container are thus suitable for the detection and diagnosis of low-grade infections with highly problematic pathogens, e.g. those selected from the group consisting of Staphylococcus aureus, Staphylococcus epidermidis and other Staphylococcus spp., Corynebacterium spp., Streptococcus spp., Enterococcus spp., Propionibacterium spp., etc.
The invention is further illustrated and specified by five figures and one example.
The shape and dimensions of the container shown in
The shape and dimensions of the container shown in
An explanted hip prostheses was placed in a container comprising an inner shape and inner dimensions, which were adapted to the outside shape and dimensions of the hip prostheses during manufacturing by injection moulding. After insertion of the hip prostheses, the lid 2 was sealed to the container body 1. Thereafter, the container was completely filled with Ringer's solution using a sterile syringe. 10 ml Ringer's solution were necessary in order to fill the free space between the explanted hip prostheses 5 and the inside wall of the container body 1.
The container was vortexed for 30 seconds using a vortex-mixer, and then subjected to sonication (frequency, 40±2 kHz; and power density 0.22±0.04 kV/cm2, in an aqua sonic model 750 T ultrasound bath (VWR scientific products)) for 5 min followed by additional vortexing for 30 seconds. The resulting sonicated fluid was removed under sterile conditions with a sterile syringe from the container without opening the container. The sonicated fluid was plated in 0.5 ml aliquots onto aerobic and anaerobic sheep-blood agar plates
For comparison, synovial fluid was obtained from a subject and inoculated in 0.1 ml aliquots onto aerobic and anaerobic shape-blood agar plates (BD diagnostic systems).
The aerobic and anaerobic sheep-blood agar plates from both sample types were incubated at 35 to 37° Celsius in 5 to 7% carbon dioxide aerobically and anaerobically for 5 days and 7 days, respectively.
Always 6 parallel samples were analysed from both sample groups, synovial fluid samples and sonication samples, respectively.
The results are shown in table 1:
S aureus
S. epidermidis
Streptococcus
Enterococcus
Corynebacterium
Propioni-
bacterium acnes
Fusobacterium
The above results show that with the container of the present invention, a concentration of pathogens eluted from an explanted hip prostheses occurs. Some of the pathogens are either not detectable in synovial fluid or are detectable but without reliability.
In contrast, due to the concentration effect achieved by using the container of the present invention in combination with ultrasound techniques, it is possible to detect and diagnose pathogenic infections in almost each sample with high reliability.
To better illustrate the container and method disclosed herein, a non-limiting list of examples is provided here:
In Example 1, a container for an implant can be provided that includes a container body defining at least one of an inner shape, inner dimensions, or an inner volume adapted to at least one of an outer shape, outer dimensions, or an outer volume of an implant.
In Example 2, the container of Example 1 can optionally be configured such that the inner volume of the container body is between 10% and 30% larger than the outer volume of the implant.
In Example 3, the container of any one of or any combination of Examples 1-2 can optionally be configured to further include a lid at a proximal end of the container body.
In Example 4, the container of Example 3 can optionally be configured such that the lid comprises a means to fix the implant inside the container.
In Example 5, the container of any one of or any combination of Examples 1-4 can optionally be configured to further include at least one of an injection hole or a membrane
In Example 6, the container of any one of or any combination of Examples 1-5 can optionally be configured such that the container body comprises a thermo-formable plastic or a plastic capable of injection moulding.
In Example 7, the container of Example 6 can optionally be configured such that the container body comprises a plastic capable of injection moulding that is selected from the group consisting of polypropylene, acrylic glass, polystyrene (PS), copolymers of polystyrene (PS), polyamide (PA) and polyoxymethylene (POM).
In Example 8, the container of Example 6 can optionally be configured such that the container comprises a thermo-formable plastic selected from the group consisting of polyvinylchloride (PVC), polyethyleneterephthalate (PET), polystyrole (PS), polypropylene, acrylnitrile-butadiene-styrole (ABS), polyaryletherketone (PAEK), and polyether ether ketone (PEEK).
In Example 9, the container of any one of or any combination of Examples 1-6 can optionally he configured such that the container comprises polypropylene, without addition of deforming supporting agents, plasticizers and biocides.
In Example 10, a method for controlling the infection of prostheses or prosthetic component can be provided that includes explanting a prosthesis or prosthetic component; inserting the prosthesis or prosthetic component into a container, the container including a container body and a lid, the container body defining at least one of an inner shape, inner dimensions, or an inner volume adapted to at least one of an outer shape, outer dimensions, or an outer volume of a prosthesis or prosthetic component; sealing the lid of the container; adding a sterile elution solution to the container; sonicating the container together with the prosthesis or prosthetic component and the elution solution inside in an ultrasonic bath; taking aliquot samples from the container under sterile conditions; and analyzing the aliquot samples for microbial infections.
In Example 11, the method of Example 10 can optionally be configured such that an already explanted prosthesis or prosthetic component is used.
In Example 12, the method of any one of or any combination of Examples 10-11 can optionally be configured to further include identifying specific bacterial strains.
In Example 13, the method of Example 12 can optionally be configured such that the specific bacterial strains are selected from Staphylococcus aureus, Staphylococcus epidermidis and other Staphylococcus spp., Corynebacterium spp., Streptococcus spp., Enterococcus spp. and Propionibacterium spp.
In Example 14, the method of any one of or any combination of Examples 10-13 can optionally be configured such that the prosthesis or prosthetic component is selected from the group consisting of a knee prosthesis, a hip prosthesis, a shoulder prosthesis, an artificial joint, a limb salvage, a trauma nail, a screw, and a plate.
In Example 15, the container or method of any one of or any combination of Examples 1-14 can optionally be configured such that all elements or options recited are available to use or select from.
Number | Date | Country | Kind |
---|---|---|---|
15154328.7 | Feb 2015 | EP | regional |