Phenotypic and molecular characterization of CTX-M extended-spectrum beta-lactamase-producing Escherichia coli isolates in Shiraz, Iran.

INTRODUCTION The aim of this study was to detect the prevalence of the extended-spectrum beta-lactamase (ESBL)-encoding CTX-M gene in Escherichia coliisolates. METHODS Phenotypic screening of 376 E. coli isolates for ESBL was conducted using disk diffusion. ESBL-producing isolates were tested using PCR and specific primers. The bla(CTX-M) cluster was identified using the RFLP method, and its genotype was sequenced. RESULTS From 202 ESBL-producing E. coli , 185 (91.5%) possessed CTX-M genes. CTX-M-1 subtypes were found in 98% of the isolates. The bla(CTX-M) gene was identical to CTX-M-15. CONCLUSIONS A high prevalence of CTX-M-1-producing E. coli apparently exists in Shiraz, Iran.