ABSTRACT
BACKGROUND: Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella spp. isolates are clinically resistant to all the beta-lactams except for carbapenems. The most important task facing clinical microbiologists today is the reliable detection of ESBL-producing microorganisms. There is currently a little reliable methods designed specifically for the detection of ESBLs in isolates of E. coli and Klebsiella spp. that can be performed easily in a clinical laboratory. This study was designed to evaluate the ability of the Vitek GNS 121 card to detect the ESBL-producing E. coli and Klebsiella spp. METHODS: One hundred and twenty-two isolates of E. coli, 141 of K. pneumoniae, and 3 of K. oxytoca from patients of the Kosin Medical Center, Pusan, Korea were tested. Antimicrobial susceptibilities were tested by the disk diffusion method. And the double disk synergy (DDS) test and the Vitek GNS 121 card determined the ESBL-production. RESULTS: Among the 135 DDS-positive isolates (K. peumoniae, 104; E. coli, 28; K. oxytoca, 3), 131 isolates (K. pneumoniae, 103; E. coli, 25; K. oxytoca, 3) showed positive results with the Vitek GNS 121 card as well. And all the isolates of K. pneumoniae (37) and E. coli (94) showed negative results with both the DDS test and the Vitek GNS 121 card except for 1 isolate of E. coli. The Vitek GNS 121 card showed 97% ESBL detection-sensitivity, 99% specificity and 99% positive predictive value. Three isolates of E. coli and 1 of K. pneumoniae resistant to cefoxitin showed positive results with the DDS test but showed negative results with the Vitek GNS 121 card. CONCLUSIONS: The Vitek GNS 121 card seems to be adequate for routine use in the detection of ESBL-producing isolates of E. coli and Klebsiella in clinical microbiology laboratories. Also, additional evaluation should be taking place on its detection ability for other members of the ESBL-producing Enterobacteriaceae.