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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

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.

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

8. 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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MRSASelect is a selective and differential chromogenic medium for 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 and healthcare workers to screen for MRSA colonization. MRSASelect is not intended to diagnose MRSA infection nor to guide or monitor treatment of infection. Results can be interpreted after 18 - 28 hours incubation.

The Bio-Rad MRSASelect is a selective and differential chromogenic culture medium for the qualitative detection of MRSA from anterior nares specimens. Results can be interpreted after 18 - 28 hours incubation.

Here's an analysis of the acceptance criteria and study proving the device meets them, based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The document does not explicitly state pre-defined acceptance criteria for the performance metrics (sensitivity, specificity, PPV, NPV). However, it reports the device's performance, and since the 510(k) was cleared, it can be inferred that these reported values were deemed acceptable by the regulatory body.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size: A total of 200 surveillance samples.
• Data Provenance: The study was conducted at "two geographically diverse hospitals" with "fresh anterior nares surveillance specimens." This indicates the data is prospective and originated from clinical settings, likely within the country where the Bio-Rad MRSASelect is seeking approval (France is the sponsor, but the 510(k) is for the US market, so the hospitals would likely be in the US or a similar regulatory region). The document doesn't explicitly state the country of origin but implies clinical relevance for the 510(k) submission.

3. Number of Experts Used to Establish Ground Truth for the Test Set and Qualifications

The document does not explicitly mention the number of experts or their qualifications for establishing the ground truth. It describes the ground truth process as "Routine culture was defined as isolation of Staphylococci on Trypticase Soy Agar with 5% blood, with identification confirmed by coagulase and Oxacillin susceptibility using E-Test." This implies standard laboratory procedures were followed, which are typically performed by trained medical laboratory scientists or microbiologists.

4. Adjudication Method for the Test Set

The document does not describe any specific adjudication method (like 2+1 or 3+1). The ground truth was established through a defined "routine culture" process, which is a laboratory standard rather than a subjective expert assessment requiring adjudication.

5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study

No, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study was not done. This study evaluates a diagnostic aid where human readers interpret results, and the document describes a standalone diagnostic test (culture medium) where the output is directly observed (colony growth and color) rather than interpreted subjectively by multiple readers. The device performs the detection, not aids human interpretation of complex images.

6. Standalone Performance

Yes, a standalone performance study was done. The entire performance evaluation focuses on the Bio-Rad MRSASelect culture medium's ability to detect MRSA directly from samples, independent of human interpretation other than observing the results of the culture. The results (sensitivity, specificity, PPV, NPV) are reported for the device itself against the routine culture gold standard.

7. Type of Ground Truth Used

The ground truth used was routine culture and laboratory confirmation. Specifically:

• Isolation of Staphylococci on Trypticase Soy Agar with 5% blood.
• Identification confirmed by coagulase test.
• Oxacillin susceptibility confirmed using E-Test.

This is a robust and long-established method for confirming bacterial identification and antibiotic resistance.

8. Sample Size for the Training Set

The document does not mention a separate training set. The performance data provided is for the evaluation of the finished product, not for the development or training of the chromogenic medium formulation itself. Culture media are typically developed through iterative formulation and testing, but the 510(k) submission focuses on the final product's clinical performance.

9. How the Ground Truth for the Training Set Was Established

Since no separate training set is mentioned in the provided text, the method for establishing its ground truth is also not described.

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MRSASelect is a selective and differential chromogenic medium for 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 and healthcare workers to screen for MRSA colonization. MRSASelect is not intended to diagnose MRSA infection nor to guide or monitor treatment of infection.

The Bio-Rad MRSASelect is a selective and differential chromogenic culture medium for the qualitative detection of MRSA from anterior nares specimens. The selectivity of this medium is based on the presence of an antibiotic/antifungal mixture and an optimized salt concentration and that inhibits the growth of yeast 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.

Here's an analysis of the Bio-Rad MRSASelect Culture Media device, based on the provided 510(k) submission information:

1. Table of Acceptance Criteria and Reported Device Performance

The submission does not explicitly state pre-defined acceptance criteria for the performance metrics (sensitivity, specificity, PPV, NPV). However, the device performance is compared against two different "ground truth" methods: Routine Culture and CHROMagar. We can infer that the reported performance metrics were deemed acceptable by the FDA for substantial equivalence.

2. Sample Size Used for the Test Set and Data Provenance

• Sample Size: A total of 3013 anterior nares samples were evaluated.
• Data Provenance:
  • Country of Origin: Not explicitly stated, but the study was conducted at "three geographically diverse hospitals." This suggests the data is likely from the country where these hospitals are located, which could be France (where Bio-Rad is headquartered) or potentially the US given the submission to the FDA.
  • Retrospective or Prospective: Prospective. The study mentions "fresh surveillance specimens of the anterior nares samples," indicating real-time collection for the study.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts

The submission does not specify the number of experts or their qualifications involved in establishing the ground truth. It refers to "Routine Culture which was defined as isolation on Staphylococci on Trypticase Soy Agar with 5% blood, with identification confirmed by Coagulase and Oxacillin susceptibility." While these are standard laboratory procedures, the expertise for their interpretation is implied to be within usual clinical laboratory practice, but no specific expert qualifications are provided.

4. Adjudication Method for the Test Set

The submission does not describe an adjudication method for the test set. The results are presented as direct comparisons between the MRSASelect medium and the reference methods (Routine Culture and CHROMagar). This typically implies a direct comparison of results without a separate ad-hoc adjudication process for discordant results, though standard lab protocols for resolving discrepancies or verifying results would be assumed.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, If So, What Was the Effect Size of How Much Human Readers Improve with AI vs Without AI Assistance

This document describes a diagnostic culture medium, not an AI-powered device. Therefore, a Multi-Reader Multi-Case (MRMC) comparative effectiveness study focusing on human reader improvement with/without AI assistance is not applicable and was not performed.

6. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done

Again, this is a culture medium, not an algorithm. The "standalone" performance described here is the performance of the culture medium itself, interpreted by laboratory personnel, in detecting MRSA. There is no AI algorithm involved.

7. The Type of Ground Truth Used

Two types of ground truth were used:

• Routine Culture: Defined as "isolation on Staphylococci on Trypticase Soy Agar with 5% blood, with identification confirmed by Coagulase and Oxacillin susceptibility." This is a gold standard for bacterial identification and susceptibility testing in microbiology.
• BD BBL™ CHROMagar™ MRSA: This is a predicate device, which itself functions as a selective and differential chromogenic medium for MRSA detection. While a predicate, it is used here as a comparative reference, implying its results are also considered a reliable truth for comparison.

8. The Sample Size for the Training Set

The submission does not explicitly mention a "training set" as this is a traditional diagnostic assay (culture medium) and not a machine learning model. Therefore, the concept of a separate training set for algorithm development is not applicable here. The entire 3013 samples represent the validation/test set for the device's performance.

9. How the Ground Truth for the Training Set Was Established

As no training set (in the machine learning sense) was used, this question is not applicable. The existing knowledge and established methods of microbiology (e.g., specific enzyme activities, antibiotic resistance, chromogenic reactions) form the basis for how the culture medium is designed to detect MRSA.

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