(210 days)
VITEK® 2 AST-Gram Negative Fosfomycin 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 AST-Gram Negative Fosfomyoin is a quantitative test. Fosfomycin 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:
Escherichia coli
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 sigmificant 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(1) and Gerlach(0). 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 Fosfomycin (≤4 - ≥256 ug/mL) has the following concentrations in the card: 2, 8, 16 and 64 ug/mL (equivalent standard method concentration by efficacy in ug/mL).
The provided text describes the performance of the VITEK® 2 AST-GN Fosfomycin device for antimicrobial susceptibility testing. Here's a breakdown of the requested information:
1. Table of Acceptance Criteria and Reported Device Performance:
The document refers to the "FDA Class II Special Controls Guidance Document: Antimicrobial Susceptibility Test (AST) Systems; Guidance for Industry and FDA (Issued August 28, 2009)" for acceptance criteria. While the specific numerical acceptance criteria (e.g., minimum percentage for %EA and %CA, maximum percentage for VME, ME, mE) are not explicitly stated in the provided text, the reported device performance is given in Table 2.
| Metric | Acceptance Criteria (Implicit from FDA Guidance) | Reported Device Performance (Enterobacterales - E. coli) |
|---|---|---|
| %EA (Essential Agreement) | Not explicitly stated, but device demonstrated acceptable performance | 99.2% (377/380) |
| VME (Very Major Errors) | Not explicitly stated, but device demonstrated acceptable performance | 0.0% (0/14) |
| ME (Major Errors) | Not explicitly stated, but device demonstrated acceptable performance | 0.0% (0/365) |
| mE (Minor Errors) | Not explicitly stated, but device demonstrated acceptable performance | 0.3% (1/380) |
| %CA (Category Agreement) | Not explicitly stated, but device demonstrated acceptable performance | 99.7% (379/380) |
2. Sample Size Used for the Test Set and Data Provenance:
- Test Sample Size: 380 isolates for Escherichia coli (Enterobacterales). The reported performance values (e.g., 377/380 for %EA, 379/380 for %CA) confirm this.
- Data Provenance: The study was an "external evaluation conducted with fresh and stock clinical isolates, as well as a set of challenge strains." This indicates a prospective study using a mix of clinical and challenge strains. The country of origin is not specified.
3. Number of Experts Used to Establish Ground Truth and Qualifications:
This information is not provided in the given text.
4. Adjudication Method for the Test Set:
This information is not provided in the given text.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study:
No MRMC study was done, as this is an antimicrobial susceptibility testing system, not a device that involves human readers interpreting cases.
6. Standalone Performance:
Yes, a standalone performance study was done. The VITEK® 2 AST-GN Fosfomycin demonstrated performance by comparing its results with the "CLSI agar dilution reference method." This indicates the algorithm (device) performed the susceptibility testing independently.
7. Type of Ground Truth Used:
The ground truth used was the CLSI agar dilution reference method. This is considered a gold standard for antimicrobial susceptibility testing.
8. Sample Size for the Training Set:
The document does not explicitly state the sample size for a training set. The study focuses on the "external evaluation" of the device's performance against a reference method. AST systems like VITEK 2 typically rely on established microbiological principles rather than machine learning models requiring large training sets in the same way an image analysis AI might.
9. How the Ground Truth for the Training Set Was Established:
As there's no mention of a separate training set in the context of machine learning, this information is not applicable/provided. If a "training set" were to be conceptualized for an AST system, it would relate to the initial development and calibration of the system's algorithms against established reference methods, which is part of the overall design and development process for such devices. The "CLSI agar dilution reference method" serves as the benchmark against which the device's accuracy is continually validated.
§ 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.”