Multicenter Clinical Evaluation of Vitek 2 Meropenem-Vaborbactam for Susceptibility Testing of Enterobacterales and Pseudomonas aeruginosa.

The carbapenem/beta-lactamase inhibitor meropenem-vaborbactam (MEV) used to treat complicated urinary tract infections and pyelonephritis in adults was approved in 2017 by the U.S. Food and Drug Administration (FDA). Here, we evaluated Vitek 2 MEV (bioMérieux, Durham, NC) compared to the reference broth microdilution (BMD) method. Of 449 Enterobacterales isolates analyzed per FDA/CLSI breakpoints, the overall performance was 98.2% essential agreement (EA), 98.7% category agreement (CA), and 0% very major errors (VME) or major errors (ME). For 438 FDA intended-for-use Enterobacterales isolates, performance was 98.2% EA, 98.6% CA, and 0% VME or ME. Evaluable EA was 81.0%, but with only 42 on-scale evaluable results. Individual species demonstrated EA and CA rates of ≥90% without any VME or ME. When evaluated using European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, overall Vitek 2 MEV performance for Enterobacterales and Pseudomonas aeruginosa demonstrated 97.3% EA, 99.2% CA, 2.3% VME, and 0.6% ME (after error resolution: 97.3% EA, 99.4% CA, 2.2% VME, and 0.4% ME) compared to the reference BMD method. Performance for P. aeruginosa included 92.2% EA, 97.4% CA, 0% VME, and 3.0% ME (after error resolution: 92.2% EA, 98.7% CA, 0% VME, and 1.5% ME). Performance for Enterobacterales included 98.2% EA, 99.6% CA, 3.0% VME, and 0.2% ME. Evaluable EA was 80.6% but was based on only 67 evaluable results. These findings support Vitek 2 MEV as an accurate automated system for MEV susceptibility testing of Enterobacterales and P. aeruginosa and could be an alternate solution to the manual-labor-intensive reference BMD method.

Multicenter Evaluation of Ceftazidime-Avibactam Susceptibility Testing of Enterobacterales and Pseudomonas aeruginosa on the Vitek 2 System.

In this multisite study, Vitek 2 AST-Gram-Negative Ceftazidime/Avibactam test results for 1,073 isolates (866 Enterobacterales and 207 Pseudomonas aeruginosa) were compared to the Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BMD) reference method. The results were analyzed for essential agreement (EA), category agreement (CA), major error rates, and very major error rates following FDA/ISO performance criteria using the FDA-recognized CLSI/EUCAST breakpoints (sensitive [S], ≤8/4 µg/ml; resistant [R], ≥16/4 µg/ml). The overall EA was 94.5% (1,014/1,073) and CA was 98.7% (1,059/1,073). No very major errors were reported. The major error rate was 1.4% (14/998). Out of 14 major errors, 9 were within EA. Based on the EA and lack of an intermediate category for ceftazidime-avibactam (CZA), the adjusted major error rate for FDA criteria was 0.5% (5/998). The performance for ISO criteria after error resolutions included EA of 94.5% (1,014/1,073), CA of 98.9% (1,061/1,073), major error of 1.2% (12/998), and no very major error. Vitek 2 met the ISO and FDA criteria of ≥95% reproducibility and ≥95% quality control (QC) results within acceptable ranges for QC organisms. Vitek 2 overall performance for Enterobacterales and P. aeruginosa met or exceeded the FDA and ISO performance criteria; thus, it is a reliable alternative to the BMD reference method for routine CZA susceptibility testing.