Frequency of E. coli clinical isolates producing blaSHV and blaTEM extended-spectrum beta-lactamases

Production of extended-spectrum beta-lactamase enzymes (ESBLs) in E. coli creates many problems for patients. These enzymes are located on transferable elements and can hydrolyze penicillins, broad-spectrum cephalosporins, and aztreonam. This study aimed to determine the clinical isolates of E. coli producing ESBLs of blaSHV and blaTEM in the city of Zanjan.
This cross-sectional study was performed on 200 E. coli isolates from clinical samples, including urine, feces, and secretions. The samples were cultured on EMB agar medium and the isolates were confirmed with various diagnostic tests. Then the sensitivity of strains to antibiotics and the production of ESBLs were determined by disc diffusion and combined disc methods, respectively. Finally, the presence of blaSHV and blaTEM genes was investigated by PCR using specific primers.
Amoxicillin had the highest resistance by 68.5% (137 isolates) and imipenem the lowest by zero percent. Resistance to the studied antibiotics were as follows; co-trimoxazole 46.5% (93 isolates), cefotaxime 34.5% (69 isolates), ceftazidime 31.5% (63 isolates), cefepime 29.5% (59 isolates), gentamycin 28.5% (57 isolates), aztreonam 45% (90 isolates), ciprofloxacin 25.5% (51 isolates), co-amoxiclave 18.5% (37 isolates), cefoxitin 19% (38 isolates), and amikacin 4.5% (9 isolates). According to the combined disc test, 66 strains (33%) were ESBL-producing enzymes and the frequency of blaTEM and blaSHV genes was 46.9% (31 isolates) and 56% (37 isolates), respectively.
Given the resistance of ESBL strains to existing antibiotics and the ability to transfer these genes to other clinical isolates, performing antibiotic sensitivity tests and detection of ESBLs in laboratories is necessary for reducing treatment failure.