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VITEK® 2 Gram Negative Piperacillin/tazobactam is designed for antimicrobial susceptibility testing of gram-negative organisms and is intended for use with the VITEK® 2 Compact Systems as a laboratory aid in the determination of in vitro susceptibility to antimicrobial agents. VITEK 2 Gram Negative Piperacillin/tazobactam is a quantitative test. Piperacillin/ tazobactam has been shown to be active against most strains of the organisms listed below according to the FDA label for the antimicrobial.

Active in vitro and in clinical infections Klebsiella pneumoniae Acinetobacter baumanii Escherichia coli Pseudomonas aeruginosa

Active in vitro but their clinical significance is uknown:

Proteus vulgaris

Providencia rettgeri

Providencia stuartii

Citrobacter koseri Morqanella morganii Proteus mirabilis

Salmonella enterica Serratia marcescens

The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK® 2 and VITEK® 2 Compact Systems 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 Negative Piperacillin/Tazobactam is designed for antimicrobial susceptibility testing of Acinetobacter baumanii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Citrobacter koseri, Morganii, Proteus mirabilis, Proteus vulgaris, Providencia rettgeri, Providencia stuartii, Salmonella enterica and Serratia marcescens. It 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. The antimicrobial presented in VITEK 2 AST Cards is in concentrations equivalent by efficacy to standard method concentrations in mod/ml. The VITEK 2 AST Cards are essentially miniaturized versions of the doubling dilution 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 System automatically fills, seals and places the card into the incubator/reader. The VITEK 2 Compact has a manual filling and sealing operation. 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 an analysis of the acceptance criteria and the study that demonstrates the device meets these criteria, based on the provided text:

Device Name: VITEK® 2 Gram Negative Piperacillin/Tazobactam (≤ 4 - ≥ 128 µg/ml)

1. Table of Acceptance Criteria and Reported Device Performance:

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

• Sample Size: Not explicitly stated as a numerical value for the test set. The document mentions "fresh and stock clinical isolates" were used.
• Data Provenance: The study was an "external evaluation" designed to confirm performance by comparing it with the CLSI broth microdilution reference method. The text does not specify the country of origin of the data or whether it was retrospective or prospective.

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

• Number of Experts: Not mentioned.
• Qualifications of Experts: Not mentioned.

4. Adjudication Method for the Test Set:

• Not explicitly stated. The ground truth method (CLSI broth microdilution) is a standardized laboratory method, so expert adjudication in the traditional sense (e.g., radiologists reviewing images) is not applicable here.

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:

• No, an MRMC comparative effectiveness study was not done. This device is an automated antimicrobial susceptibility test system, not an imaging device requiring human reader interpretation in the context of AI assistance. The performance is assessed against a reference laboratory method.

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

• Yes, the core of the study is a standalone performance evaluation. The VITEK® 2 system is an automated device designed to determine antimicrobial susceptibility. Its performance (Essential Agreement, Category Agreement) is directly compared to a reference method (CLSI broth microdilution), which represents its "standalone" diagnostic accuracy without human intervention in the susceptibility determination process itself.

7. The Type of Ground Truth Used:

• The ground truth used was the CLSI broth microdilution reference method. This is considered the gold standard for determining minimum inhibitory concentrations (MICs) of antimicrobials.

8. The Sample Size for the Training Set:

• The document does not provide information regarding a separate training set. The VITEK 2 system's underlying algorithm for determining MICs and interpretive categories would have been developed and validated previously, and this submission focuses on the performance of a specific antimicrobial-device combination (Piperacillin/Tazobactam on the VITEK 2 AST-GN card) against a reference method. It's possible the "training" (development) of the MIC interpretation algorithms for the VITEK 2 system happened prior to this specific submission, and this study is a validation for a new antimicrobial.

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

• Since no specific training set for this particular antimicrobial validation is mentioned, the method for establishing its ground truth is also not specified. However, for the underlying VITEK 2 system's development, it would have involved extensive testing against reference methods like CLSI broth microdilution.

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