Association between biofilm production and antibiotic resistance in Escherichia coli strains isolated from patients with urinary infection in Isfahan during 2017

Urinary tract infection (UTI) is one of the most common bacterial infections, and a significant cause of morbidity in humans. Uropathogenic Escherichia coli (UPEC) is known as the primary cause of UTI and due to its ability to form biofilm results in high level resistance to different classes of antibiotics. Biofilm formation is a major determinant for the persistence and recurrence of UTI. In this study we aimed to determine the prevalence of biofilm producing UPECs and the relationship between antibiotic resistance and the quantity and quality of biofilm formation in patients with UTI in Isfahan.

During 2017, a total of 213 suspected E. coli isolates were collected from patients with UTI in a referral hospital in Isfahan and were identified using common biochemical and PCR confirmatory diagnostic tests. Production of curli/cellulose, and, biofilm formation was assessed using qualitative Congo red agar (CRA) and quantitative microtiter plate (MTP) methods, respectively. Biofilm producing strains were tested for susceptibility to 17 antibiotics using disk diffusion method by the guidelines of Clinical & Laboratory Standards Institute (CLSI).

A total of 166 strains (78%) were identified and confirmed as E. coli using common biochemical and PCR tests. According to the results of qualitative CRA and quantitative MTP assays, 39 strains (23%) were able to form curli and/or cellulose and were biofilm positive. The highest resistance rate of biofilm producing E. coli strains was against ampicillin followed by cefotaxime, cefpodoxime and ceftriaxone. On the other hand, carbapenems and aminoglycosides were also the most effective antibiotics against UPEC infections.

The results of the present study indicating the high prevalence of antibiotic resistant biofilm producing UPEC strains among patients with UTI in Isfahan. Moreover, a direct relationship between the strong biofilm production and high level antibiotic resistance was also found.