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The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK 2 System for the automated quantitative or qualitative susceptibility testing of isolated colonies for the most clinically significant aerobic gram-negative bacilli, Staphylococcus spp., Enterococcus spp., Streptococcus agalactiae, and S. pneumoniae.

VITEK 2 Gram Positive Ertapenem is designed for antimicrobial susceptibility testing of Staphylococcus aureus (methicillin susceptible strains only), and Streptococcus agalactiae. VITEK 2 Gram Positive Ertapenem is a qualitative test. It is intended for use with the VITEK 2 System as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents.

The VITEK 2 AST Cards are essentially miniaturized versions of the doubling rily n technique for determining the minimum inhibitory concentration (MIC) microdilution methodology. The bacterial isolate to be tested is diluted to a standardized concentration in 0.45% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK 2 automatically fills, seals and places the card into the incubator/reader. The VITEK 2 monitors the growth of each well in the card over a defined period of time (up to 18 hours). At the completion of the incubation cycle, a report is generated that contains the MIC value along with the interpretive category result for each antibiotic contained on the card.

Here's a breakdown of the acceptance criteria and study details for the VITEK® 2 Gram Positive Ertapenem device, based on the provided text:

Acceptance Criteria and Device Performance

Note: The specific numerical performance for "Overall Category Agreement" is not explicitly stated as a percentage in the document, only that it demonstrated "acceptable results." The criteria is mentioned as "90.0% Overall Category Agreement" but the actual performance against this criteria is not given numerically, only that it was "acceptable."

Study Details

2. Sample sizes used for the test set and data provenance

• Test Set: Not explicitly stated how many clinical isolates and stock challenge strains were used. The document mentions "fresh and stock clinical isolates and stock challenge strains."
• Data Provenance: Not explicitly stated (e.g., country of origin). The document mentions "external evaluations" which implies multi-site, but locations are not specified. The study used both prospective ("fresh clinical isolates") and retrospective ("stock clinical isolates and stock challenge strains") data.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts

• Not specified in the provided text.

4. Adjudication method for the test set

• Not specified in the provided text. The text only mentions "comparison with the NCCLS agar dilution reference method" as the ground truth.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done

• No, an MRMC study was not done. This device is an automated antimicrobial susceptibility testing system, not a device requiring human interpretation for its primary output.

6. If a standalone (i.e. algorithm only without human-in-the loop performance) was done

• Yes, this was a standalone study. The VITEK® 2 system is an automated device designed to produce direct results (MIC values and interpretive category results) without human intervention in the interpretation of the susceptibility itself. The study compared the device's automated results against a reference method.

7. The type of ground truth used

• Expert Consensus: Not explicitly stated.
• Pathology: Not applicable for an antimicrobial susceptibility test.
• Outcomes Data: Not applicable for an antimicrobial susceptibility test.
• Reference Method: The ground truth was established by the NCCLS reference agar dilution method. This is an established laboratory standard for determining antimicrobial susceptibility.

8. The sample size for the training set

• The document does not explicitly mention a separate "training set" or its size. The study describes "testing of Staphylococcus aureus (methicillin susceptible strains only), and Streptococcus agalactiae" using clinical and challenge strains. It is implied that the system's underlying algorithm was previously developed and validated, and this submission focuses on the performance of a new drug/organism combination on an existing system.

9. How the ground truth for the training set was established

• As no explicit "training set" is described for this submission, the method for establishing its ground truth is not detailed in the provided text. For automated susceptibility testing systems, the ground truth for developing and calibrating the algorithms would typically also be established using recognized reference methods like the NCCLS agar dilution method.

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