Teerawit TangkoskulSurapee TiengrimSupiluck OnsomangNaratchaphan PatiNalinee AswapokeeVisanu ThamlikitkulMethee ChayakulkeereeMahidol University2018-06-112018-06-112012-11-01Southeast Asian Journal of Tropical Medicine and Public Health. Vol.43, No.6 (2012), 1461-1469012515622-s2.0-84873045931https://repository.li.mahidol.ac.th/handle/20.500.14594/14553We performed extended-spectrum p-lactamase (ESBL) phenotypic testing and molecular characterization of three ESBL genes (TEM, SHV and CTX-M) and susceptibility testing by Clinical Laboratory Standards Institute (CLSI) disk diffusion method against three cephalosporins (ceftriaxone, ceftazidime, cefepime) and a cephamycin (cefoxitin) among 128 Thai Escherichia coli and 84 Thai Klebsiella pneumoniae clinical isolates. ESBL production was discovered in 62% of E. coli and 43% of K. pneumoniae isolates. All isolates susceptible to ceftriaxone were ESBL-negative. Nearly all isolates non-susceptible to ceftriaxone, ceftazidime and cefepime produced ESBL; the presence of CTX-M genes in the isolates correlated with a ceftriaxone non-susceptible phenotype. Thirty-nine of 83 isolates (47%) of ceftazidime-susceptible E. coli and 50 of 99 isolates (50.5%) of cefepime-susceptible E.coli were ESBL-producing. SHV-type B-lactamase genes were more prevalent among K. pneumoniae than £. coli isolates. CTX-M was the major ESBL gene harbored by ESBL-producers in both E. coli and K. pneumoniae isolates. Non-CTX-M ESBL-producers were found only among K. pneumoniae isolates. This study reveals an increase in ESBL-producing Enterobacteriaceae among Thai isolates and demonstrates gaps in the current CLSI disk diffusion susceptibility guidelines; it indicates the results of ceftazidime and cefepime disk diffusion susceptibility testing using CLSI criteria should be interpreted with caution.Mahidol UniversityMedicineArticleSCOPUS