BACKGROUND AND OBJECTIVE: Extended-spectrum beta-lactamase (ESBL) enzymes hydrolyze cephalosporins and penicillins. This study aimed to determine the frequency of Escherichia coli strains producing SHV, TEM and CTX-M &beta-lactamase genes and their association by inducing antibiotic resistance.

METHODS: In this cross-sectional study, 55 E. coli strains were isolated from urinary samples and cultured on eosin methylene blue (EMB) agar and CHROMagar. After biochemical examinations, antibiotic susceptibility test was performed using the disk-diffusion method according to the guidelines of the Clinical & Laboratory Standards Institute (CLSI). In addition, the presence of blaCTX-M, blaTEM and blaSHV genes was evaluated using specific multiplex polymerase chain reaction (PCR) primers.

FINDINGS: In this study, the highest antibiotic resistance was observed against penicillin and erythromycin (96% and 94.5%, respectively), while the highest susceptibility was reported for ciprofloxacin and imipenem (67.2%). Out of 55 samples, 26(47.27%) had the TEM gene, and CTX-M gene was detected in 41 (74.54%) samples. Moreover, TEM and CTX-M genes were simultaneously detected in 32.72% of the samples, while in six samples (10.9%), neither of these genes were present. The SHV gene was not detected in any of the samples.

CONCLUSION: According to the results of this study, the production of ESBL was identified in 70% of the investigated E. coli isolates. Therefore, accurate and timely medical care, as well as the use of appropriate antibiotics, is required to prevent the outbreak of ESBL-producing E. coli strains.