(25 days)
VITEK® 2 Gram Positive Gatifloxacin is designed for antimicrobial susceptibility testing of Staphylococcus aureus (methicillin susceptible strains only) and Staphylococcus saprophyticus. 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 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 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.
The VITEK® 2 Gram Positive Gatifloxacin device is an antimicrobial susceptibility testing system. The acceptance criteria and supporting study details are as follows:
1. Acceptance Criteria and Reported Device Performance
| Acceptance Criteria | Reported Device Performance |
|---|---|
| Overall Essential Agreement (compared to NCCLS reference agar dilution method) | 99.5% |
| Reproducibility | Acceptable |
| Quality Control | Acceptable |
2. Sample Size and Data Provenance
- Test Set Sample Size: Not explicitly stated as a single number, but implied to be sufficient for an "external evaluation conducted with fresh and stock clinical isolates and stock challenge strains."
- Data Provenance: The nature of "fresh and stock clinical isolates" suggests a mix of prospective (fresh clinical isolates) and retrospective (stock clinical isolates) data. The geographic origin of the data is not specified.
3. Number of Experts and Qualifications for Ground Truth for Test Set
Not applicable. The ground truth for the test set was established using a reference method (NCCLS agar dilution method), not through expert interpretation of device outputs.
4. Adjudication Method for the Test Set
Not applicable. The ground truth was established by the NCCLS reference agar dilution method, which is a standardized laboratory procedure, not requiring adjudication in the context of human interpretation.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
Not applicable. This device is an automated antimicrobial susceptibility testing system, not an imaging or diagnostic device that requires human interpretation of outputs. Therefore, no MRMC study comparing human readers with and without AI assistance was performed.
6. Standalone Performance Study
Yes, a standalone study was performed. The device's performance (VITEK® 2 Gram Positive Gatifloxacin) was compared directly against the NCCLS reference agar dilution method without human intervention in the device's determination of susceptibility. The device itself is an algorithm-driven system that provides an interpretive category result.
7. Type of Ground Truth Used
The ground truth used was the NCCLS reference agar dilution method. This is a laboratory-based, standardized reference method for determining minimum inhibitory concentrations (MICs) of antimicrobial agents.
8. Sample Size for the Training Set
The document does not explicitly state the sample size used for the training set. It describes an "external evaluation" for performance confirmation, implying a test set, but does not detail a separate training phase or its associated data.
9. How the Ground Truth for the Training Set Was Established
The document does not explicitly describe a separate training set or how its ground truth was established. The overall evaluation focused on comparing the device's performance to the NCCLS reference agar dilution method as the gold standard.
§ 866.1645 Fully automated short-term incubation cycle antimicrobial susceptibility system.
(a)
Identification. A fully automated short-term incubation cycle antimicrobial susceptibility system is a device that incorporates concentrations of antimicrobial agents into a system for the purpose of determining in vitro susceptibility of bacterial pathogens isolated from clinical specimens. Test results obtained from short-term (less than 16 hours) incubation are used to determine the antimicrobial agent of choice to treat bacterial diseases.(b)
Classification. Class II (special controls). The special control for this device is FDA's guidance document entitled “Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA.”