Frequency of Biofilm Producing Escherichia coli Strains Isolated from Patients with Urinary Tract Infection in Isfahan. 2017

Urinary tract infections (UTIs) are some of the most common bacterial infections, and a significant cause of morbidity in all age groups that incur large financial costs to health-care systems. Uropathogenic Escherichia coli (UPEC) is the primary cause of UTIs and due to its high resistance to most classes of antibiotics, results in treatment failure. UPEC strains possess various virulence factors such as the ability to form biofilm which plays an important role in UTIs. The formation of biofilms by UPEC on or within bladder epithelial cells and as well as on urinary catheters is responsible for persistent infections which leading to recurrences. In this study we aimed to determine the prevalence of biofilm producing E. coli strains isolated from patients with UTI in Isfahan.

During 2017, a total of 213 E. coli isolates were collected from patients with UTI in a reference hospital in Isfahan and were identified using common biochemical and PCR confirmatory diagnostic tests. The ability of E. coli strains to form curli and cellulose was measured using qualitative Congo red agar assay and a quantitative microtiter plate assay was employed to test the biofilm forming capacity of the strains.

A total of 166 strains were identified and confirmed as E. coli using PCR test. Using qualitative Congo red agar plate assay, 127 strains (77%) exhibited saw morphotype and were not able to produce curli and cellulose. The other 39 strains (23%), produced curli and cellulose and were biofilm positive, in which, 38, 59 and 3% exhibited rdar, bdar and pdar morphotypes, respectively. Also, the results of microtiter plate assay showed that all of 39 curli and cellulose producing strains were biofilm positive in which 18, 26 and 56% of strains were able to form strong, moderate and weak biofilm, respectively.

The results of this study revealed the high prevalence of E. coli associated UTIs among different sexes and age groups in Isfahan. Biofilm production is closely related to antibiotic resistance and nowadays, biofilm forming UPEC strains are global public health concern. All strong biofilm producer UPEC strains, were able to form curli and cellulose simultaneously; which indicating the important role of these two compounds in the intensity of biofilm formation. Therefore, providing new therapeutic strategies and powerful compounds for destroying or inhibition of curli and cellulose will play an essential role in solving the clinical problems caused by biofilm of E. coli.