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VITEK® 2 Streptococcus Moxifloxacin is designed for antimicrobial susceptibility testing of Streptococcus species 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 Streptococcus Moxifloxacin is a quantitative test. Moxifloxacin has been shown to be active against most isolates of the microorganisms listed below, according to the FDA label for this antimicrobial.

Active in vitro and in clinical infections
Streptococcus anginosus
Streptococcus constellatus
Streptococcus pneumoniae (including multi-drug resistant isolates [MDRSP]*)
Streptococcus pyogenes

*MDRSP. Multi-drug resistant Streptococcus pneumoniae includes isolates previously known as PRSP (Penicillin resistant S. pneumoniae), and are isolates resistant to two or more of the following antibiotics: penicillin (MIC) ≥2 mcg/mL). 2nd generation cephalosporins (for example, cefuroxime), macrolides. tetracyclines, and trimethoprim/sulfamethoxazole.

The following in vitro data are available. but their clinical significance is unknown.

Gram-positive bacteria
Streptococcus agalactiae
Streptococcus viridans group

The VITEK® 2 Antimicrobial Susceptibility Test (AST) is intended to be used with the VITEK® 2 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 spp., and clinically significant yeast.

The VITEK® 2 AST card is essentially a miniaturized, abbreviated and automated version of the doubling dilution technique for determining the minimum inhibitory concentration (MIC). 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 test contained on the card.

The VITEK® 2 AST-ST Moxifloxacin for Streptococcus species has the following concentrations in the card: 0.5. 1, 4 and 8 µg/ml (equivalent standard method concentration by efficacy in µg/mL). The MIC result range for the VITEK 2 card is ≤ 0.06 -> 4 µg/mL.

Here's an analysis of the acceptance criteria and study details for the VITEK® 2 AST-ST Moxifloxacin device, based on the provided text:

Acceptance Criteria and Device Performance for VITEK® 2 AST-ST Moxifloxacin

1. Table of Acceptance Criteria and Reported Device Performance

The acceptance criteria for antimicrobial susceptibility testing devices are typically defined by regulatory bodies and guidance documents (e.g., FDA, CLSI) and are based on various performance metrics like Essential Agreement (EA), Category Agreement (CA), and the rates of major (maj), very major (vmj), and minor (min) discrepancies. The provided document details the performance in these categories. While explicit numerical "acceptance criteria" are not listed as such, the observed performance is presented in comparison to the expected standards for such devices.

Note: The specific numerical acceptance criteria for EA, CA, and discrepancy rates are often derived from FDA guidance documents and CLSI standards. The reported performance clearly demonstrates that the device meets or exceeds typical expectations for these metrics. The text notes "acceptable results" for the VITEK® 2 Compact, reinforcing that the performance aligns with regulatory requirements.

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

• Sample Size for Test Set:
  • Clinical Isolates: 941 viable clinical isolates (out of 951 tested, with 10 failing to grow).
  • Challenge Isolates: 159 isolates.
  • Combined (Clinical + Challenge): 1100 isolates.
• Data Provenance: The study was conducted at three external clinical sites. The isolates included both clinical specimens (majority of the 951) and stock isolates (229 of the 951 clinical isolates, indicating a mix of prospective clinical collection and possibly retrospective stock isolates for diversity). No specific country of origin is mentioned, but "external clinical sites" typically refers to institutions within the country where the submission is made (USA in this context, given the FDA submission). The nature of the clinical and challenge isolates suggests a mix of retrospective (stock) and prospective (fresh clinical) data types.

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

The ground truth for the test set was established using the CLSI approved broth microdilution reference method. This is a standardized laboratory procedure, not typically relying on individual "experts" for ground truth determination in the same way, for example, image interpretation would. The expertise comes from adherence to the CLSI protocol for performing the reference method. Therefore, the concept of "number of experts" and their "qualifications" for establishing ground truth in this context is not applicable in the traditional sense of human consensus.

4. Adjudication Method for the Test Set

The adjudication method is not explicitly described as a specific consensus process (like 2+1 or 3+1). Instead, the performance of the VITEK® 2 system is compared directly against the CLSI broth microdilution reference method, which serves as the gold standard. Discrepancies (vmj, maj, min errors) are identified and quantified based on this comparison. The decision-making process for these discrepancies would likely follow predefined internal bioMérieux quality control protocols and regulatory guidelines for AST device validation, rather than expert adjudication of each discordant result.

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

No MRMC comparative effectiveness study comparing human readers with and without AI assistance was performed. This device is an Automated Antimicrobial Susceptibility Testing (AST) system, meaning it replaces manual subjective interpretation of susceptibility rather than assisting human readers. Its effectiveness is measured by its agreement with a standardized reference method (broth microdilution), not by human-in-the-loop performance.

6. Standalone Performance Study (Algorithm Only)

Yes, a standalone performance study was done. The entire performance evaluation (Essential Agreement, Category Agreement, and discrepancy rates) directly measures the algorithm's output (MIC values and interpretive categories S/I/R) against the reference method's output. The VITEK® 2 system is an automated device, and its reported performance is its standalone (algorithm only) performance. The results for the VITEK® 2 Auto Dilution, VITEK® 2 Manual Dilution, and VITEK® 2 Compact Manual Dilution all represent standalone device performance.

7. Type of Ground Truth Used

The ground truth used was the Clinical and Laboratory Standards Institute (CLSI) approved broth microdilution testing conditions (reference method) for determining Minimum Inhibitory Concentration (MIC). This is a well-established and universally accepted laboratory method for antimicrobial susceptibility testing.

8. Sample Size for the Training Set

The document does not explicitly state the sample size for the training set. The provided data pertains to validation testing of the device's performance. For FDA 510(k) submissions of AST devices, the focus is on the performance against a defined test set. Information on internal training data used during the development of the VITEK® 2's interpretive algorithm is typically considered proprietary and not included in such summaries.

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

As with the training set size, the document does not specify how the ground truth for the training set was established. However, it is highly probable that the ground truth for any internal training data would also have been established using comprehensive reference methods, similar or identical to the CLSI broth microdilution method used for the validation test set, to ensure accurate algorithm development. This is standard practice in the development of in vitro diagnostic devices.

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