Frequency of antibiotic resistance and genes encoding integrons among uropathogenic Escherichia coli strains isolated from patients with urinary tract infection in Tehran during 2021

Urinary tract infections (UTIs) are the most common severe bacterial infections seen in clinical settings worldwide. It is known that Escherichia coli (E. coli) is the most prevalent bacterial pathogen that causes UTIs. Antibiotic resistance leads to higher medical costs, prolonged hospital stay, and increased mortality. UTIs caused by extended spectrum β-lactamase (ESBL) producing E. coli account for one of the major therapeutic and epidemiologic challenges. In this study we determined the prevalence of uropathogenic E. coli strains isolated from patients with UTI in Tehran, Iran. Moreover, the antibiotic resistance and presence of different classed of integrons among strains was also assessed.

During 2021, a total of 126 E. coli isolated from patients with UI were collected from a referral hospital laboratory in Tehran, and confirmed using phenotypic tests and polymerase chain reaction (PCR) by specific primers for tufA gene. Resistance of strains to 17 antibiotics was determined using disk diffusion method according to the guidelines of clinical and laboratory standards institute (CLSI), and ceftazidime and cefotaxime resistant strains were tested for ESBL production by cefotaxime and ceftazidime disks each alone and in combination with clavulanic acid. The presence of classes I-III integrons among strains was determined using separate PCR tests.

All 126 tested isolates were confirmed as E. coli. All strains (100%) were resistant to ampicillin and the highest rate of resistance was found to ceftriaxone followed by cefpodoxime, ceftazidime and cefotaxime, respectively. Also, low rate of resistance to meropenem, imipenem and kanamycin was observed among strains, respectively. Moreover, 75% of strains were identified as ESBL producing strains, and all 3 classes of integrons were detected among strains, in which integron class I was the dominant one.

Results of the present study indicated the high prevalence of UPEC strains with different classes of integrons and resistance to first line antibiotics among patients with UI in Tehran. The emergence and dissemination of antibiotic resistant pathogenic bacteria could be an important threat to human health.