Rare Case of Failure by an Automated System To Detect Extended-Spectrum β-Lactamase in a Cephalosporin-Resistant Klebsiella pneumoniae Isolate

Several tests used for the detection of extended-spectrum-β-lactamase (ESBL)-producing enterobacterial isolates have been evaluated in past studies. Detection of ESBLs by the Vitek GNS-506 panel (Bio-Mérieux, Marcy l’Etoile, France) is based on the comparison of the reduction in growth by cefotaxime-clavulanate and ceftazidime-clavulanate with the reduction caused by the cephalosporins alone. The test has been proven reliable for the detection of ESBLs in Klebsiella pneumoniae andEscherichia coli and more effective than the double-disk synergy test (DDST) (3). The Vitek system is widely used in Greek hospitals.