Evaluation of the Vitek-2 extended-spectrum β-lactamase test against non-duplicate strains of Enterobacteriaceae producing a broad diversity of well-characterised β-lactamases

The Vitek-2 extended-spectrum β-lactamase (ESBL) test was assessed using a collection of 94 ESBL-positive and 71 ESBL-negative non-duplicate isolates of Enterobacteriaceae. These isolates produced a wide diversity of well-characterised β-lactamases, including 61 different ESBLs, two class A carbapenemases and various species-specific β-lactamases. ESBL detection was performed using (i) the conventional synergy test as recommended by the Comité de l'Antibiogramme de la Société Française de Microbiologie, (ii) the CLSI phenotypic confirmatory test for ESBLs, and (iii) the Vitek-2 ESBL test. For Escherichia coli and klebsiellae, the sensitivity/specificity values were 97.3%/96.9% for the synergy test, 91.8%/100% for the CLSI phenotypic confirmatory test, and 91.8%/100% for the Vitek-2 ESBL test. For other organisms, the sensitivity/specificity values were 100%/97.4% for the synergy test, 90.5%/100% for the CLSI phenotypic confirmatory test, and 90.5%/100% for the Vitek-2 ESBL test. The Vitek-2 ESBL test seemed to be an efficient method for routine detection of ESBL-producing isolates of Enterobacteriaceae, including isolates producing AmpC-type enzymes.