Study on the antimicrobial resistance and genotypes of extended-spectrum β-lactamases in Escherichia coli isolates

Objective: To study the relationship between antibiotic resistance and extended-spectrum β-lactamases(ESBLs) genes in clinical isolates of E.coli.Methods: Antibiotic susceptibility was tested by Kirby-Bauer disk diffusion method and ESBLs production was detected by CLSI phenotypic confirmarory test in E.coli isolates.The β-lactamases genes were identified by PCR and sequencing.Results: Fourty-nine of 117 strains collected were ESBLs-producing E.coli and all of them were resistant to ampicillin,piperacillin,cefazolin,cefuroxime.The resistance rates to cefotaxime,ceftriaxone,cefpodoxime,and cefoperazone were more than 95%,but only 41.8% to ceftazidime.The resistance rates to piperacillin-tazobactam and cefoperazone-sulbactam were 8.1% and 18.4%,respectively,to imipenem was 0.0%.ESBLs gene was found in all ESBLs-producing isolates,and CTX-M-14 genotype was dominated(87.8%).Conclusions: ESBLs-producing E.coli are prevelance in our hospital and most of them are multidrug resistant strains.CTX-M-14 is the main genotype of ESBLs,and the second is CTX-M-3 genotype.No other genotype of ESBLs was detected.