VITEK 2 AST-Gram Negative Cefazolin (=<1-=>32 µg/mL)

The VITEK 2 AST-Gram Negative Cefazolin is an automated antimicrobial susceptibility test card designed for clinical laboratories to determine the in vitro susceptibility of gram-negative bacteria (Enterobacterales) to the antibiotic cefazolin. The card contains 64 wells with premeasured cefazolin concentrations and is used with VITEK 2 Systems to generate quantitative minimum inhibitory concentration (MIC) values and interpretive category results (susceptible, intermediate, or resistant).

The device uses a miniaturized microdilution technique with three cefazolin concentrations (1, 2, and 8 µg/mL). The card is automatically filled, sealed, and incubated by VITEK 2 systems, which monitor well growth over time and analyze growth patterns to determine MIC. Key difference from predicate: this clearance extends compatibility to the VITEK 2 Compact Pro instrument system, which was not available at the time of the original predicate clearance.

CLSI (Clinical and Laboratory Standards Institute) broth microdilution reference method, incubated 16-20 hours. FDA Susceptibility Test Interpretive Criteria (STIC) breakpoints for Enterobacterales (≤2 susceptible, 4 intermediate, ≥8 resistant).

The device is substantially equivalent because it uses identical test methodology, inoculum preparation, card format, analysis algorithms, and antimicrobial concentrations and breakpoints as the predicate device (K222073). The only difference is the expanded indications for use to explicitly specify five tested Enterobacterales species and compatibility with an additional instrument platform (VITEK 2 Compact Pro). Performance testing demonstrated 97.6% essential agreement and 86.8% category agreement with the CLSI reference standard, supporting equivalent clinical performance.