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VITEK® 2 Gram Negative Cefotaxime is designed for antimicrobial susceptibility testing of Gram negative bacilli 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 is a quantitative test. Cefotaxime 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 clinical infections: Acinetobacter spp. Citrobacter spp. Enterobacter spp. Escherichia.coli Klebsiella spp. (including Klebsiella pneumoniae) Morganella morganii Proteus mirabilis Proteus vulgaris Providencia rettgeri Providencia stuartii Serratia marcescens

In vitro data available but clinical significance is unknown: Providencia spp. Salmonella spp. (including Salmonella typhi)

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., and clinically significant yeast.

The VITEK® 2 AST Cards are essentially miniaturized versions of the doubling dilution technique for determining the minimum inhibitory concentration (MIC) microdilution methodology.

The isolate to be tested is diluted to a standardized concentration in 0.45 - 0.50% 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 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 antimicrobial contained on the card.

Here's a breakdown of the acceptance criteria and study information for the VITEK® 2 AST Gram Negative Cefotaxime device, based on the provided text:

Acceptance Criteria and Device Performance

Study Information

2. Sample size used for the test set and data provenance:

• Test Set Size: Not explicitly stated as a single number. The study utilized "fresh and stock clinical isolates, as well as a set of challenge strains."
• Data Provenance: The text does not specify the country of origin. It indicates the data is from an "external evaluation" and involved "clinical isolates," suggesting retrospective or prospective clinical samples were used, but the exact nature (retrospective/prospective) is not explicitly detailed for the clinical isolates.

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

• Number of Experts: This information is not provided in the text.
• Qualifications: This information is not provided in the text.

4. Adjudication method for the test set:

• Adjudication Method: This information is not provided in the text. The ground truth was established by comparing the device's performance against the CLSI broth microdilution reference method, which is a standardized laboratory method, not typically involving expert adjudication in the same way an image interpretation study would.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, and if so, what was the effect size of how much human readers improve with AI vs without AI assistance:

• MRMC Study: No, an MRMC comparative effectiveness study was not performed. This device is an automated antimicrobial susceptibility testing system, not an AI-assisted diagnostic tool for human readers.

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

• Standalone Performance: Yes, the study evaluated the standalone performance of the VITEK® 2 AST-GN Cefotaxime system. The system automatically performs the test, monitors growth, and generates a report with MIC values and interpretive categories. The reported Essential Agreement and Category Agreement are measures of this standalone performance compared to the reference method.

7. The type of ground truth used:

• Ground Truth: The ground truth was established using the CLSI broth microdilution reference method, incubated at 16-20 hours, as defined in the FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems. This is a recognized standard laboratory method for determining antimicrobial susceptibility.

8. The sample size for the training set:

• Training Set Size: This information is not provided. The VITEK® 2 system is a diagnostic device that performs susceptibility testing, not typically a machine learning model that undergoes a training phase in the conventional sense with a distinct "training set" of patient data. The development of such a system would involve extensive method development and validation using various strains, but this is different from a machine learning training set.

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

• Training Set Ground Truth: As above, a traditional "training set" with ground truth in the context of machine learning is not applicable here. The fundamental principles and performance of the VITEK® 2 system were established against the CLSI broth microdilution reference method during its development and validation.

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