Sensitivity and specificity of various beta-lactam antibiotics and phenotypical methods for detection of TEM, SHV and CTX-M extended-spectrum beta-lactamases.
The aim of this study was to compare the sensitivity and specificity of six different beta-lactam antibiotics using five phenotypical tests for detection of extended spectrum beta-lactamases (ESBLs) based on synergism of beta-lactam antibiotics and clavulanate. Experiments were performed on a set of 80 Klebsiella pneumoniae strains and 105 Escherichia coli strains with previously characterized ESBLs (SHV, TEM and CTX-M). ESBLs were detected by five different phenotypical methods: MIC (minimum inhibitory concentration) determination of beta-lactam antibiotics with and without clavulanate, double-disk synergy test (DDST), inhibitor-potentiated disk-diffusion test (IPDDT), CLSI-Clinical and Laboratory Standard Institution (former NCCLS) combined-disk-test, and modified MAST-disk-diffusion test (MAST-DD-test). Seven antibiotics were tested as indicators of ESBL production: ceftazidime, cefotaxime, ceftriaxone, aztreonam, ceftibuten, cefpodoxime and cefepime. Ceftazidime and aztreonam were the best indicators for SHV-5, SHV-12 and TEM beta-lactamases whereas cefotaxime and ceftriaxone were the most sensitive in detection of SHV-2 and CTX-M beta-lactamases in DDST, IPDDT and CLSI test. MIC determination of beta-lactam antibiotics with and without clavulanate was the most sensitive method. DDST was the least sensitive test. Double-disk synergy test, which is the most frequently used test for detection of ESBLs in routine laboratories, was the least sensitive independently of the indicator antibiotic. Since MIC determination is a very laborious and time consuming method, we would recommend the NCCLS combined disk test or IPDD test for detection of ESBLs in routine laboratories with 5 mm zone augmentation breakpoint.
Bedenic
B
B
Department of Microbiology, School of Medicine, University of Zagreb, Zagreb, Croatia. branka.bedenic@zg.htnet.hr
Vranes
J
J
Mihaljevic
Lj
Lj
Tonkic
M
M
Sviben
M
M
Plecko
V
V
Kalenic
S
S
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D019818:Clavulanic Acid / Q000494:pharmacology*; D004357:Drug Synergism; D004926:Escherichia coli / Q000187:drug effects; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects; D008826:Microbial Sensitivity Tests / Q000379:methods*; D010641:Phenotype; D012680:Sensitivity and Specificity; D018440:beta-Lactam Resistance / Q000187:drug effects* / Q000235:genetics; D001618:beta-Lactamases / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D047090:beta-Lactams / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D019818:Clavulanic Acid; D001618:beta-Lactamases