Prevalence and characterization of beta-lactamase-producing Escherichia coli isolates from a tertiary care hospital in India

BACKGROUND: The purpose of the study was to determine the prevalence and characterize the resistance profiles of Escherichia coli isolated from various clinical specimens by various phenotypic and genotypic methods. MATERIALS AND METHODS: A total of 196 consecutive, nonduplicate strains of clinically significant E. coli isolated from various clinical specimens were included in the study. Identification and antimicrobial susceptibility testing was performed by using Vitek-2 system (Biomerieux, France). Phenotypic detection of extended spectrum beta-lactamase (ESBLs), Amp-C-β lactamase (Amp C), and carbapenemase production was done by various combination of disc diffusion methods, minimum inhibitory concentration determination by E-test, followed by polymerase-chain-reaction for the detection of β-lactamase-encoding genes. RESULTS: Overall prevalence of ESBLs, Amp C, and carbapenemase production was found to be 88.3%, 42.2%, and 65.1% by the phenotypic detection methods. Our study also revealed high resistance rates against other antibiotics such as cefepime (89%), cefotaxime (95.4%), ceftazidime (85.4%), ceftriaxone (91.8%), cefpodoxime (92.7%), aztreonam (56.3%), piperacillin/tazobactam (89.2%), and ticarcillin/clavulanic acid (76.3%). The most prevalent ESBL gene was bla(TEM) (67.30%), and least prevalent ESBL gene was bla(VEB) (2.61%). In case of Amp C, bla(FOX) gene (21.9%) was predominant. Among the genes encoding for carbapenemases, the most common gene was bla(NDM) (61.7%) followed by bla(VIM) (30.8%), bla(KPC) (10.6%), bla(OXA-48) (5.3%), and bla(IMP) (2.1%). CONCLUSION: Our findings suggest a high rate of ESBLs, Amp C, and carbapenemase production among the E. coli isolates. A combination of both phenotypic and genotypic methods would be ideal for better characterization of resistance patterns among the E. coli isolates.