(262 days)
MRSASelect™II is a selective and differential chromogenic medium for:
A) The qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings. The test can be performed on anterior nares specimens from patients to screen for MRSA colonization. MRSASelect™II is not intended to diagnose MRSA infection nor to guide or monitor treatment of infection. A negative result does not preclude MRSA nasal colonization. Concomitant cultures are necessary to recover organisms for identification, antimicrobial susceptibility testing, or epidemiological typing. Results can be interpreted after 18 to 28 hours incubation.
B) The qualitative detection of methicillin-resistant Staphylococcus aureus (MRSA) from skin and soft tissue wound specimens. The MRSASelect™II is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA from patients with skin and soft-tissue infections. Concomitant cultures and antimicrobial susceptibility testing are necessary for all skin and soft-tissue wound specimens. MRSASelect™I is not intended to guide, or monitor treatment for MRSA infection, or provide results of susceptibility to methicillin. Results can be interpreted after 18 to 28 hours incubation.
MRSASelect™I is a selective medium for the detection and direct identification of MRSA. The selectivity of this medium is based on the presence of an antibiotic/antifungal mixture and an optimized salt concentration that inhibits the growth of yeasts and the majority of Gram negative and Gram positive bacteria, with the exception of methicillin-resistant staphylococci. Identification is based on the cleavage of a chromogenic substrate by a specific enzymatic activity of Staphylococcus aureus, leading to a strong pink coloration of the Staphylococcus aureus colonies. Plates may be read within 18-28 hours incubation:
- Methicillin-resistant Staphylococcus aureus produces pink colonies on MRSASelect™II;
- . Coagulase negative methicillin-resistant staphylococci may not grow or may grow as colorless or white colonies;
- Methicillin-susceptible staphylococci (MSS) are inhibited.
Here's an analysis of the provided text, focusing on the acceptance criteria and the study proving the device meets them, presented in the requested format.
This document describes the premarket notification (510(k)) for the MRSASelect™II device, a culture medium for detecting methicillin-resistant Staphylococcus aureus (MRSA). The information provided is for a diagnostic device (culture medium) and not an AI device. Therefore, some of the requested categories (e.g., number of experts for ground truth, MRMC study, training set information) are not directly applicable or are not detailed in the same way they would be for an AI/ML medical device submission. However, an effort will be made to extract comparable information where possible.
Acceptance Criteria and Reported Device Performance
The acceptance criteria for a diagnostic culture medium are typically established as performance targets for sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) against a reference method. These are not explicitly stated as "acceptance criteria" with numerical thresholds to be met, but the clinical performance data provided demonstrates the device's accuracy.
Table 1: Acceptance Criteria (Implied Performance Targets) and Reported Device Performance
| Performance Metric | Implied Acceptance Criteria (Typical for such devices) | Reported Device Performance (Wound Samples - Table 3) | Reported Device Performance (Anterior Nares Samples - Table 4) |
|---|---|---|---|
| Sensitivity | High (e.g., >90%) | 96.7% (95% C.I.: 96.0%-97.5%) | 91.0% (95% C.I.: 86.8%-93.9%) |
| Specificity | High (e.g., >90%) | 95.4% (95% C.I.: 94.5%-96.2%) | 98.3% (95% C.I.: 97.6%-98.8%) |
| Positive Predictive Value (PPV) | High | 82.1% (95% C.I.: 80.5%-83.7%) | 86.2% (95% C.I.: 81.6%-89.9%) |
| Negative Predictive Value (NPV) | High | 99.2% (95% C.I.: 98.9%-99.6%) | 98.9% (95% C.I.: 98.4%-99.3%) |
Note on "Acceptance Criteria": For traditional in vitro diagnostic devices like culture media, the "acceptance criteria" are typically defined internally by the manufacturer during product development and validation, often based on predicate device performance or clinical utility. The FDA then evaluates whether the provided performance data supports the claim of substantial equivalence. The tables above reflect the achieved performance which the FDA deemed acceptable for substantial equivalence.
Study Details
Given that this is a 510(k) for a culture medium (not an AI device), some of the requested information directly pertaining to AI/ML device studies will not be present in the document.
-
Sample size used for the test set and the data provenance:
- Total Clinical Samples: 3,252 prospective valid wound and anterior nares specimens.
- Wound Samples (Test Set): 842 specimens.
- Anterior Nares Samples (Test Set): 2,410 specimens.
- Data Provenance:
- Country of Origin: United States.
- Retrospective or Prospective: Prospective. Specimens were collected from 2013 to 2016.
-
Number of experts used to establish the ground truth for the test set and the qualifications of those experts:
- This information is not directly stated in the document as it would be for an AI imaging study involving human readers. For diagnostic culture media, ground truth is established by specific, well-defined laboratory reference methods. The document describes a multi-step microbiological process for establishing ground truth, involving culture enrichment, subculturing, Gram stain, agglutination tests, tube coagulase, and for MRSA confirmation PBP2a testing and mecA-mediated oxacillin resistance testing. The execution of these laboratory methods implies the involvement of qualified laboratory personnel (e.g., clinical microbiologists, medical technologists), but specific numbers or qualifications are not specified in the document in the format relevant to expert readers of AI output.
-
Adjudication method (e.g., 2+1, 3+1, none) for the test set:
- Not applicable in the context of human reader adjudication for an AI device. For discordant results between the device and the reference method, "Discordant analysis" was performed (e.g., for wound samples, PBP2a test was used; for anterior nares, specific non-S. aureus and MSSA determinations were made). This is a laboratory-based adjudication of the samples themselves, not an adjudication of human interpretations.
-
If a multi-reader, multi-case (MRMC) comparative effectiveness study was done:
- No. An MRMC study is relevant for comparing human reader performance with and without an AI device. This submission is for a culture medium, not an AI device.
-
If a standalone (i.e., algorithm only without human-in-the-loop performance) was done:
- Yes, effectively. The performance of the MRSASelect™II device itself, without human interpretation beyond reading the chromogenic results, was assessed against the established reference methods. This "standalone" performance is what the sensitivity, specificity, PPV, and NPV data represent.
-
The type of ground truth used (expert consensus, pathology, outcomes data, etc.):
- Laboratory Reference Method / Microbiological Culture Confirmation: The ground truth was established by using standard microbiological culture enrichment broth methods (Tryptic Soy Broth with 6.5% NaCl) followed by definitive identification tests for Staphylococcus aureus (Gram stain, slide agglutination, tube coagulase) and confirmation of methicillin resistance (PBP2a testing for anterior nares; mecA-mediated oxacillin resistance testing using cefoxitin disk for wound samples, with PBP2a for discordant wound samples). This is a gold standard for bacterial identification and resistance.
-
The sample size for the training set:
- This document describes a clinical performance study (test set) for device validation, not an AI/ML model. Therefore, there's no explicitly defined "training set" in the context of machine learning. The device design and refinement would have been based on internal R&D, potentially involving earlier, smaller studies or characterization data, but these are not disclosed as a "training set" in this document.
-
How the ground truth for the training set was established:
- Not applicable as there is no specific "training set" described for an AI/ML model. The design and analytical validation of the culture medium (e.g., Analytical Sensitivity (Inclusivity) testing with 54 characterized MRSA strains, Analytical Specificity (Cross Reactivity) with 109 strains, Precision/Reproducibility using ATCC® strains) demonstrate how the device's fundamental properties were confirmed against known bacterial strains/isolates, which serve as an equivalent to a "ground truth" for analytical performance.
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Image /page/0/Picture/0 description: The image contains the logos of the Department of Health & Human Services and the Food and Drug Administration (FDA). The Department of Health & Human Services logo is on the left, and the FDA logo is on the right. The FDA logo includes the text "FDA U.S. FOOD & DRUG ADMINISTRATION" in blue.
December 28, 2017
Bio-Rad % Fran White President MDC Associates, LLC 180 Cabot Street Beverly, Massachusetts 01915
Re: K171061
Trade/Device Name: MRSASelect II Regulation Number: 21 CFR 866.1700 Regulation Name: Culture medium for antimicrobial susceptibility tests Regulatory Class: Class II Product Code: JSO Dated: November 30, 2017 Received: December 1, 2017
Dear Fran White:
We have reviewed your Section 510(k) premarket notification of intent to market the device referenced above and have determined the device is substantially equivalent (for the indications for use stated in the enclosure) to legally marketed predicate devices marketed in interstate commerce prior to May 28, 1976, the enactment date of the Medical Device Amendments, or to devices that have been reclassified in accordance with the provisions of the Federal Food, Drug, and Cosmetic Act (Act) that do not require approval of a premarket approval application (PMA). You may, therefore, market the device, subject to the general controls provisions of the Act. The general controls provisions of the Act include requirements for annual registration, listing of devices, good manufacturing practice, labeling, and prohibitions against misbranding and adulteration. Please note: CDRH does not evaluate information related to contract liability warranties. We remind you, however, that device labeling must be truthful and not misleading.
If your device is classified (see above) into either class II (Special Controls) or class III (PMA), it may be subject to additional controls. Existing major regulations affecting your device can be found in the Code of Federal Regulations, Title 21, Parts 800 to 898. In addition, FDA may publish further announcements concerning your device in the Federal Register.
Please be advised that FDA's issuance of a substantial equivalence determination does not mean that FDA has made a determination that your device complies with other requirements of the Act or any Federal statutes and regulations administered by other Federal agencies. You must comply with all the Act's requirements, including, but not limited to: registration and listing (21 CFR Part 807); labeling (21 CFR Part 801 and Part 809); medical device reporting of medical device-related adverse events) (21 CFR 803); good manufacturing practice requirements as set forth in the quality systems (QS) regulation (21 CFR
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Part 820); and if applicable, the electronic product radiation control provisions (Sections 531-542 of the Act); 21 CFR 1000-1050.
Also, please note the regulation entitled, "Misbranding by reference to premarket notification" (21 CFR Part 807.97). For questions regarding the reporting of adverse events under the MDR regulation (21 CFR Part 803), please go to http://www.fda.gov/MedicalDevices/Safety/ReportaProblem/default.htm for the CDRH's Office of Surveillance and Biometrics/Division of Postmarket Surveillance.
For comprehensive regulatory information about mediation-emitting products, including information about labeling regulations, please see Device Advice (https://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/) and CDRH Learn (http://www.fda.gov/Training/CDRHLearn). Additionally, you may contact the Division of Industry and Consumer Education (DICE) to ask a question about a specific regulatory topic. See the DICE website (http://www.fda.gov/DICE) for more information or contact DICE by email (DICE@fda.hhs.gov) or phone (1-800-638-2041 or 301-796-7100).
Sincerely,
Ribhi Shawar -S For
Uwe Scherf, M.Sc., Ph.D. Director Division of Microbiology Devices Office of In Vitro Diagnostics and Radiological Health Center for Devices and Radiological Health
Enclosure
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Indications for Use
510(k) Number (if known) K171061
Device Name MRSASelect™II
Indications for Use (Describe)
MRSASelect™II is a selective and differential chromogenic medium for:
A) The qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings. The test can be performed on anterior nares specimens from patients to screen for MRSA colonization. MRSASelect™II is not intended to diagnose MRSA infection nor to guide or monitor treatment of infection. A negative result does not preclude MRSA nasal colonization. Concomitant cultures are necessary to recover organisms for identification, antimicrobial susceptibility testing, or epidemiological typing. Results can be interpreted after 18 to 28 hours incubation.
B) The qualitative detection of methicillin-resistant Staphylococcus aureus (MRSA) from skin and soft tissue wound specimens. The MRSASelect™II is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA from patients with skin and soft-tissue infections. Concomitant cultures and antimicrobial susceptibility testing are necessary for all skin and soft-tissue wound specimens. MRSASelect™I is not intended to guide, or monitor treatment for MRSA infection, or provide results of susceptibility to methicillin. Results can be interpreted after 18 to 28 hours incubation.
| Type of Use (Select one or both, as applicable) | |
|---|---|
| Prescription Use (Part 21 CFR 801 Subpart D) | Over-The-Counter Use (21 CFR 801 Subpart C) |
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| Date of Summary | December 12, 2017 | ||
|---|---|---|---|
| Product Name | MRSASelect™II | ||
| Sponsor | Bio-Rad Laboratories3 Boulevard Raymond Poincaré92430 Marnes-la-CoquetteFrance | ||
| Correspondent | MDC Associates, LLCFran White, Regulatory Consultant180 Cabot StreetBeverly, MA 01915Phone: (978) 927-3808Fax: (978) 927-1308Email: fran@mdcassoc.com | ||
| Device Identification | |||
| Trade or Proprietary Name: | MRSASelect™II | ||
| Common or Usual Name: | Culture Media, Antimicrobial Susceptibility Test, Excluding MuellerHinton Agar | ||
| Product Code: | ાડભ | ||
| Regulation Section: | 21 CFR 866.1700 | ||
| Product Classification: | Class II |
Intended Use
MRSASelect™II is a selective and differential chromogenic medium for:
A) The qualitative detection of nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA) to aid in the prevention and control of MRSA infections in healthcare settings. The test can be performed on anterior nares specimens from patients to screen for MRSA colonization. MRSASelect™I is not intended to diagnose MRSA infection nor to guide or monitor treatment of infection. A negative result does not preclude MRSA nasal colonization. Concomitant cultures are necessary to recover organisms for identification, antimicrobial susceptibility testing, or epidemiological typing. Results can be interpreted after 18 to 28 hours incubation.
B) The qualitative detection of methicillin-resistant Staphylococcus aureus (MRSA) from skin and soft tissue wound specimens. The MRSASelect™II is indicated for use in conjunction with other laboratory tests and clinical data available to aid in the identification and diagnosis of MRSA from patients with skin and soft-tissue infections. Concomitant cultures and antimicrobial susceptibility testing are necessary for all skin and soft-tissue wound specimens. MRSASelect™II is not intended to guide, or monitor treatment for MRSA infection, or provide results of susceptibility to methicillin. Results can be interpreted after 18 to 28 hours incubation.
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Device Description
MRSASelect™I is a selective medium for the detection and direct identification of MRSA. The selectivity of this medium is based on the presence of an antibiotic/antifungal mixture and an optimized salt concentration that inhibits the growth of yeasts and the majority of Gram negative and Gram positive bacteria, with the exception of methicillin-resistant staphylococci. Identification is based on the cleavage of a chromogenic substrate by a specific enzymatic activity of Staphylococcus aureus, leading to a strong pink coloration of the Staphylococcus aureus colonies. Plates may be read within 18-28 hours incubation:
- Methicillin-resistant Staphylococcus aureus produces pink colonies on MRSASelect™II;
- . Coagulase negative methicillin-resistant staphylococci may not grow or may grow as colorless or white colonies;
- Methicillin-susceptible staphylococci (MSS) are inhibited.
Substantial Equivalency
The MRSASelect™I is substantially equivalent to the Bio-Rad MRSASelect™ Extended Incubation (K081212) and MRSASelect™ Wound Specimen (K100589) products. Table 1 on the following page compares the characteristics of the Bio-Rad MRSASelect™I (New Device) and the Bio-Rad MRSASelect™ Extended Incubation (K081212) and MRSASelect™ (K100589) products (Predicate Devices). The differences noted do not impact the intended use and do not raise questions as the safety and effectiveness of the test (new) device.
| SIMILARITIES | |||
|---|---|---|---|
| ProductAttribute | Primary Predicate DeviceBio-Rad MRSASelect™Extended Incubation(K081212) | Predicate DeviceBio-Rad MRSASelect™Wound Specimen(K100589) | New DeviceBio-Rad MRSASelect™IICombined Nasal and Wound Culture MediaSpecimens |
| Regulation | 21 CFR 866.1700 | 21 CFR 866.1700 | 21 CFR 866.1700 |
| Product Code | JSO | JSO | JSO |
| Device Class | Class II | Class II | Class II |
| Intended Use | MRSASelect™ is a selectiveand differential chromogenicmedium for the qualitativedetection of nasalcolonization of methicillin-resistant Staphylococcusaureus (MRSA) to aid in theprevention and control ofMRSA infections in healthcaresettings. The test can beperformed on anterior naresspecimens from patients andhealthcare workers to screenfor MRSA colonizationMRSASelect™ is not intendedto diagnose MRSA infectionnor to guide or monitortreatment of infection.Results can be interpreted | MRSASelect™ is a selectiveand differential chromogenicmedium for the qualitativedetection of methicillin-resistant S. aureus (MRSA)from skin and soft-tissuewound specimens. TheMRSASelect™ is indicated foruse in conjunction with otherlaboratory tests and clinicaldata available to aid in theidentification and diagnosisof MRSA from patients withskin and soft-tissueinfections. Concomitantcultures and susceptibilitytesting are necessary for allskin and soft-tissue woundspecimens. MRSASelect™ is | MRSASelect™II is a selective and differentialchromogenic medium for:A) The qualitative detection of nasalcolonization of methicillin-resistantStaphylococcus aureus (MRSA) to aid in theprevention and control of MRSA infections inhealthcare settings. The test can be performedon anterior nares specimens from patients toscreen for MRSA colonization. MRSASelect™II isnot intended to diagnose MRSA infection nor toguide or monitor treatment of infection. Anegative result does not preclude MRSA nasalcolonization. Concomitant cultures arenecessary to recover organisms foridentification, antimicrobial susceptibilitytesting, or epidemiological typing. Results canbe interpreted after 18 to 28 hours incubation.B) The qualitative detection of methicillin- |
Table 1: Comparison of New Device with Predicate Devices
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| SIMILARITIES | |||
|---|---|---|---|
| ProductAttribute | Primary Predicate DeviceBio-Rad MRSASelect™Extended Incubation(K081212) | Predicate DeviceBio-Rad MRSASelect™Wound Specimen(K100589) | New DeviceBio-Rad MRSASelect™IICombined Nasal and Wound Culture MediaSpecimens |
| after 18–28 hours incubation. | not intended nor to guide, ormonitor treatment for MRSAinfection, or provides resultsof susceptibility tomethicillin. Results can beinterpreted after 18 to 28hours incubation. | resistant Staphylococcus aureus (MRSA) fromskin and soft tissue wound specimens. TheMRSASelect™II is indicated for use inconjunction with other laboratory tests andclinical data available to aid in the identificationand diagnosis of MRSA from patients with skinand soft-tissue infections. Concomitant culturesand antimicrobial susceptibility testing arenecessary for all skin and soft-tissue woundspecimens. MRSASelect™II is not intended toguide, or monitor treatment for MRSA infection,or provide results of susceptibility to methicillin.Results can be interpreted after 18 to 28 hoursincubation. | |
| ProductFormat | Chromogenic agar | Chromogenic agar | Chromogenic agar |
| Read Time | 18–28 hours incubation | 18–28 hours incubation | 18–28 hours incubation |
| DIFFERENCES | |||
| ProductAttribute | Primary Predicate DeviceBio-Rad MRSASelect™Extended Incubation(K081212) | Predicate DeviceBio-Rad MRSASelect™Wound Specimen(K100589) | New DeviceBio-Rad MRSASelect™IICombined Nasal and Wound Culture MediaSpecimens |
| SpecimenType | Anterior nares | Skin and soft-tissue wound | Anterior nares and skin and soft-tissue wound |
| Inoculum | Direct and Indirect (saline) | Direct | Direct |
Performance Characteristics: Analytical Performance
Precision/Reproducibility
Assay precision was tested at three clinical sites and measured site-to-site reproducibility and lot-to-lot reproducibility using a blinded panel of eleven (11) organism suspensions. Ten ATCC® strains were used for the panel preparation. The panel members consisted of MRSA, MSSA and S. epidermidis. Results demonstrate that MRSASelect™II is reproducible across sites and lots.
Analytical Sensitivity (Recovery Study)
The percent recovery LoD was defined as the lowest dilution at which growth is observed (> 1 CFU) on MRSASelect™II with corresponding growth observed in parallel on Blood Agar Plate. The LoD of the MRSASelect™Il was determined using ATCC® 43300™ and NRS 660, two (2) well characterized MRSA strains from culture collections. The data confirm that the minimum concentration of MRSA reliably detected by MRSASelect™II is 800 CFU/mL in nasal or wounds matrix.
Analytical Sensitivity (Inclusivity)
A total of 54 characterized collection strains of MRSA (including USA300-0114, USA100, 200, 500, 600, 700, 800, and 1000) were inoculated onto MRSASelect™MI plates using saline suspensions at the
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concentration of 80-240 CFU/mL. Isolates tested included known clinically associated strains from the Network on Antimicrobial Resistance in Staphylococcus aureus (NARSA) and ATCC® collections.
Table 2: Analytical Sensitivity
| MRSASelect™ II | |||
|---|---|---|---|
| Reading times | 18 hours | 24 hours | 28 hours |
| Sensitivity | 53/54(98.1%) | 54/54(100%) | 54/54(100%) |
A total of 53/54 isolates grew as pink colonies at a concentration of 80-240 CFU/mL on MRSASelect™I after 18 hours. After 24 and 28 hours incubation all 54 isolates grew as pink colonies.
Analytical Specificity (Cross Reactivity)
A total of 109 strains from various species were evaluated at a minimum concentration of 10° CFU/mL on MRSASelect™I. Cross-reactivity was defined as growth of distinct pink colonies on MRSASelect™Il at 18, 24 and 28 hours incubation. A total of 107 out of the 109 strains were inhibited or recovered as nonpink colonies on MRSASelect™II. Two strains of MSSA produced colonies with pink coloration on MRSASelect™I. An appropriate limitation has been added to the IFU. Some MRSE (Methicillin Resistant Staphylococcus epidermidis) strains grew as white colonies within 18-28 hours on MRSASelect™. In addition, the following organisms grew as faint pink colonies when clustered together: Corynebacterium imitans, Corynebacterium jeikeium, Aerococcus viridans, Staphylococcus cohnii and Staphylococus sciuri. An appropriate limitation has been added to the IFU.
Interference Study
A total of twenty (20) medicinal substances commonly used in anterior nares and on skin and soft-tissue wound specimens were evaluated for potential interference of the chromogenic reaction of the MRSASelect™I. No interference was observed with 12/20 of them. One (1) substance (Ocean Premium Saline Nasal Spray®) reduced the quantity of growth of MRSA on MRSASelect™I and BAP without complete inhibition. Seven (7) substances (Neosynephrine®, Dristan 12h®, Ayr Saline®, Walgreens First Aid Antiseptic Spray®, Tecnu First Aid Antiseptic Pain Relieving Gel, Bactine, inhibited growth on MRSASelect™Il and BAP. Appropriate limitations have been added to the IFU.
Co-Infection/Mixed Infection
The effect of mixed cultures on the performance of MRSASelect™II was assessed by inoculating MRSA in the presence of an increasing concentration of methicillin-resistant S. epidermidis or K. pneumoniae. No impact on the growth of the MRSA was observed due to co-infection.
Validation of Transport Media
The effect of three (3) different transport media on the growth of MRSA on MRSASelect™Il was evaluated. The following transport media were used LQ STUART and LQ AMIES with or without charcoal. The use of these transport media did not decrease the recovery of MRSA on MRSASelect™M. An appropriate limitation has been added to the IFU.
Clinical Performance Characteristics
The performance of MRSASelect™II was evaluated at three (3) geographically diverse locations within the United States from 2013 to 2016. A total of 3,252 prospective valid wound and anterior nares specimens were included in the final data set and analyzed for product performance. All samples yielded
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valid results and were included in the final analysis. Performance of MRSASelect™II was evaluated against the established reference method; for wound samples a culture enrichment broth method (Tryptic Soy Broth (TSB) with 6.5% NaCl) was used. Positive TSB cultures were subcultured on Blood Agar Plates (BAP). Identification of suspected Staphylococcus aureus colonies on BAP was confirmed using Gram stain, slide agglutination test for detection of Staphylococcus aureus, tube coagulase, and mecAmediated oxacillin resistance testing using 30 µg cefoxitin disk. Similarly, for anterior nares samples, a culture enrichment broth method was used. Positive TSB cultures were subcultured on BAP. ldentification of suspected Staphylococcus aureus colonies on BAP was confirmed followed by confirmation using Gram stain, slide agglutination test for detection of Staphylococcus aureus, tube coagulase and PBP2a testing. Performance results are shown in the Table 3 and Table 4 below:
Results
Table 3: Wound Samples
| All Sites | Culture Enrichment Broth(Cefoxitin) | ||||
|---|---|---|---|---|---|
| POS | NEG | TOTAL | |||
| MRSASelectTMII(Primary Culture) | POS | 147 | 32a | 179 | |
| NEG | 5b | 658 | 663 | ||
| TOTAL | 152 | 690 | 842 | ||
| All Sites | 95% C.I. | ||||
| Sensitivity (%) | 96.7% | 96.0% | 97.5% | ||
| Specificity (%) | 95.4% | 94.5% | 96.2% | ||
| Positive Predictive Value | 82.1% | 80.5% | 83.7% | ||
| Negative Predictive Value | 99.2% | 98.9% | 99.6% |
ª Discordant analysis was performed for 27 of the 32 specimens identified as MRSA positive by MRSA was confirmed in 17 of the 27 specimens using PBP2a test.
0 Discordant analysis was performed for 5 of the 5 specimens identified as MRSA negative by MRSA was confirmed in 3 of the 5 specimens using PBP2a test.
် The overall prevalence of MRSA as determined broth culture reference method was 18% (152/842).
| Table 4: Anterior Nares Samples | ||||
|---|---|---|---|---|
| -- | -- | --------------------------------- | -- | -- |
| All Sites | Culture Enrichment Broth(PBP2a)(c) | ||||
|---|---|---|---|---|---|
| POS | NEG | TOTAL | |||
| MRSASelect™II(Primary Culture) | POS | 232 | 37(e) | 269 | |
| NEG | 23(d) | 2,118 | 2,141 | ||
| TOTAL | 255 | 2,155 | 2,410 | ||
| All Sites | 95% C.I. | ||||
| Sensitivity (%) | 91.0% | 86.8% | 93.9% | ||
| Specificity (%) | 98.3% | 97.6% | 98.8% | ||
| Pos. Predictive Value | 86.2% | 81.6% | 89.9% | ||
| Neg. Predictive Value | 98.9% | 98.4% | 99.3% |
c) PBP2a test performed from colonies on BAP after the enrichment step in TSB (PBP2a).
No further discordant resolution was conducted on those discrepant samples.
d) All 23 specimens resulted in no growth on MRSASe/ect™II.
e) Of the 37 false positives observed, a total of 25 isolates were determined to be non-S. aureus species (including 11 strains of coagulase-negative Staphylococcus); and 12 isolates were identified as methicillin-susceptible S. aureus.
-The overall prevalence of MRSA as determined by the enriched broth culture reference method was 10.6% (255/2410).
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Conclusions
The submitted information in this premarket notification is complete and supports a substantial equivalence decision.
§ 866.1700 Culture medium for antimicrobial susceptibility tests.
(a)
Identification. A culture medium for antimicrobial susceptibility tests is a device intended for medical purposes that consists of any medium capable of supporting the growth of many of the bacterial pathogens that are subject to antimicrobial susceptibility tests. The medium should be free of components known to be antagonistic to the common agents for which susceptibility tests are performed in the treatment of disease.(b)
Classification. Class II (performance standards).