Evaluation of the capability of the VITEK 2 system to detect extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates, in particular with the coproduction of AmpC enzymes.

A total of 317 Klebsiella pneumoniae and 291 Escherichia coli nonduplicate isolates were tested by the VITEK 2 system to evaluate its capability to detect extended-spectrum beta-lactamases (ESBLs) among putative ESBL-producing isolates, in particular those with the coproduction of AmpC enzymes. beta-lactamases produced by the test isolates had been characterised. The sensitivity and specificity for ESBLs were 98.9% and 98.5%, respectively. Ninety of the isolates were AmpC (CMY-2, CMY-8 or DHA-1) and ESBL (SHV and/or CTX-M) coproducers, and 74 isolates (82.2%) of them were flagged as ESBL producers. Our study indicates that the VITEK 2 system is an acceptable tool for ESBL detection among K. pneumoniae and E. coli isolates for laboratories where both imported AmpC and ESBLs are prevalent.