Antimicrobial resistance and genotypes of extended-spectrum β-lactamases in Escherichia coli

Objective To investigate the prevalence, resistance and genotypes of extended-spectrumβ-lactamases in E. coli isolates. Methods K-B disk diffusion method was used in susceptibility testing and ESBLs producers were detected by NCCLS Phenotypic Confirmatory Test (disk diffusion test) in E. coli isolates. Theβ-lactamase genes were identified by PCR and sequencing. Results The prevalence of ESBLs producers were 40. 3% and all of them were resistant to penicillins, the first, second generation cephalosporins. The resistance rates to ceftriaxone, cefotaxime, and cefoperazone were more than 95% , but only 41.6% to ceftazidime. The resistance rates to piperacillin-tazobactam, cefoperazone-sulbactam, gentamicin, trimethoprim-sulfamethoxazole, fluoroquinolones, and imipenem were 9.0% , 18. 0% , 62. 9% , 83. 1 % , 75. 3% and 0 %. ESBLs gene was positive in 98. 9% (88/89) of the E. coli strains by PCR. CTX-M-14 was the most prevalent (86. 5% , 77/89) genotype. Some ESBLs producers produced more than one type of ESBLs. Conclusions ESBLs producers are common in E. coli isolated from our hospital. Most of them are multidrug resistant. CTX-M-14 was the main genotype of ESBLs. Other genotype of ESBLs is not found.