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VITEK® 2 AST-Gram Negative Imipenem/Relebactam is designed for antimicrobial susceptibility testing of Gram Negative bacilli and is intended for use with the VITEK® 2 and VITEK® 2 Compact Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents. VITEK® 2 AST-Gram Negative Imipenem/Relebactam is a quantitative test. Imipenem/Relebactam has been shown to be active against most strains of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active in vitro and in clinical infections: Klebsiella (Enterobacter) aerogenes Enterobacter cloacae Escherichia coli Klebsiella pneumoniae Pseudomonas aeruginosa Citrobacter freundii Klebsiella oxytoca

In vitro data are available, but clinical significance is unknown Citrobacter koseri Enterobacter asburiae

The VITEK® 2 Gram-Negative Susceptibility Card is intended for use with the VITEK® 2 Systems in clinical laboratories as an in vitro test to determine the susceptibility of clinically significant aerobic Gram-negative bacilli to antimicrobial agents when used as instructed.

The principle of the VITEK® 2 AST cards is based on the microdilution minimum inhibitory concentration (MIC) technique reported by MacLowry and Marsh () and Gerlach (2). The VITEK® 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique (3).

Each VITEK® 2 AST card contains 64 wells. A control well which only contains microbiological culture media is resident on all cards. The remaining wells contain premeasured portions of a specific antibiotic combined with culture media. The bacterial or yeast isolate to be tested is diluted to a standardized concentration with 0.45 - 0.5% saline before being used to rehydrate the antimicrobial medium within the card. The VITEK® 2 System automatically fills, seals and places the card into the incubator/reader. The VITEK® 2 Compact has a manual filling, sealing and loading operation. The VITEK® 2 Systems monitor the growth of each well in the card over a defined period of time. 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.

VITEK® 2 AST-GN Imipenem/Relebactam has the following concentrations in the card: 0.25/4, 1/4, 4/4 and 16/4 ug/mL (equivalent standard method concentration by efficacy in ug/mL).

The provided text describes the 510(k) summary for VITEK® 2 AST-Gram Negative Imipenem/Relebactam, an automated antimicrobial susceptibility testing system. The study aims to demonstrate substantial equivalence to a predicate device and adherence to CLSI broth microdilution reference methods.

Here's a breakdown of the requested information based on the provided text:

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria are implied by the FDA Class II Special Controls Guidance Document (August 28, 2009) and assessed through Essential Agreement and Category Agreement. The specific numerical acceptance criteria are not explicitly stated as "acceptance criteria" but are reported as performance metrics that demonstrate acceptability.

Note on Acceptance Criteria: While the text states "acceptable performance of 95.3% Essential Agreement and 98.9% Category Agreement for Enterobacteriaceae and 96.2% Essential Agreement and 95.5% Category Agreement for P. aeruginosa," it doesn't explicitly state the pre-defined acceptance criteria (e.g., "EA must be >= 90%"). However, these reported values are presented as demonstrating "substantially equivalent performance" and "acceptable performance," strongly implying they met the underlying criteria.

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

• Sample Size for Test Set: The text mentions an "external evaluation... with fresh and stock clinical isolates, as well as a set of challenge strains." However, the exact numerical sample size (total number of isolates tested in the external evaluation) is not provided in the given text.
• Data Provenance: The text states the study was an "external evaluation" using "fresh and stock clinical isolates" and "challenge strains." This suggests the data is likely retrospective (using existing collections of isolates) and potentially prospective if fresh clinical isolates were collected during the study period. The country of origin of the data is not specified.

3. Number of Experts Used to Establish Ground Truth and Qualifications

This information is not provided in the text. The ground truth was established by the CLSI broth microdilution reference method, which is a standardized laboratory procedure, not typically relying on expert interpretation in the same way as, for example, image analysis.

4. Adjudication Method for the Test Set

This information is not applicable in the context of this study. The ground truth was established by a reference laboratory method (CLSI broth microdilution), not by human interpretation requiring adjudication.

5. If a Multi Reader Multi Case (MRMC) Comparative Effectiveness Study Was Done, and the Effect Size of Human Improvement

• MRMC Comparative Effectiveness Study: No, an MRMC comparative effectiveness study was not done. This study is evaluating the performance of an automated AST system against a reference method, not the impact of AI assistance on human readers.
• Effect Size of Human Improvement: Therefore, this information is not applicable.

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

Yes, a standalone performance study was done. The VITEK® 2 AST-GN Imipenem/Relebactam is an automated system described as a "quantitative test" that "automatically fills, seals and places the card into the incubator/reader" and "monitor[s] the growth of each well... At the completion of the incubation cycle, a report is generated." The reported performance metrics (Essential Agreement and Category Agreement) are for the device's output compared to the reference method, indicating standalone performance.

7. The Type of Ground Truth Used

The type of ground truth used was the CLSI broth microdilution reference method. This is a consensus-based, standardized laboratory method for determining antimicrobial susceptibility.

8. The Sample Size for the Training Set

This information is not provided in the text. As this is an automated system based on growth pattern analysis (not explicitly a machine learning model that requires a distinct "training set" in the common sense for AI, though it would have been developed and validated on internal data), there isn't a "training set" as might be described for a deep learning algorithm. The provided text describes the performance evaluation of the developed system.

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

This information is not provided in the text. For a system like VITEK, the underlying "ground truth" for its development would be established through extensive correlation with standard laboratory methods, similar to the CLSI broth microdilution method used for its performance evaluation.

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