Comparison of screening methods for detection of extended-spectrum beta-lactamases and their prevalence among Escherichia coli and Klebsiella species in Hong Kong.
Three tests, the disk diffusion test, the double-disc synergy test and the inhibitor-potentiated disc diffusion test, were compared for their abilities to detect production of extended-spectrum beta-lactamases (ESBL) in 702 Escherichia coli and 472 Klebsiella spp. strains from four hospitals. Eleven percent E. coli and 13% Klebsiella spp. were found to produce ESBL. As an indicator of ESBL activity, the sensitivities of the five extended-spectrum beta-lactams were as follows: cefotaxime (100%), cefpodoxime (99.3%), ceftriaxone (98.6%), aztreonam (93%) and ceftazidime (57.7%) when interpreted using the National Committee for Clinical Laboratory Standards criteria. Their positive predictive values ranged from 67.8-83.8%. Both the inhibitor-potentiated disc diffusion test and the double-disc synergy test (at three inter-disc widths of 20, 25 and 30 mm) were capable of identifying all the ESBL-producers. However, at a single inter-disc width of 30 mm, the double-disc synergy test has limited sensitivity (83.8%). As a second test for confirming ESBL activity in strains with reduced susceptibility to beta-lactams, the inhibitor-potentiated disc diffusion test is therefore a simple and reliable option.
Ho
P L
PL
Department of Microbiology, Queen Mary Hospital, University of Hong Kong, Pokfulam, China. plho@hkucc.hku.hk
Tsang
D N
DN
Que
T L
TL
Ho
M
M
Yuen
K Y
KY
D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development; D006723:Hong Kong; D006801:Humans; D007709:Klebsiella / Q000201:enzymology* / Q000254:growth & development; D001618:beta-Lactamases / Q000032:analysis*
D001618:beta-Lactamases