Comparison of Tissue Culture Plate, Congo red Agar and Tube Methods for Evaluation of Biofilm Formation among Uropathogenic E. coli Isolates

Abstract

Background and Aims: Microorganisms within biofilms,, formed on medical devices in the body are highly resistant to antimicrobial compounds and host responses and play a major role in nosocomial infections, especially urinary tract infections (UTIs). Uropathogenic Escherichia coli (UPEC) causes 50% of the hospital-acquired urinary tract infections and is capable to form biofilm in the bladder epithelium which plays an important role in its pathogenesisThe identification of biofilm producing UPEC strains by routine laboratory methods is important for the better understanding of the pathogenesis of this bacterium in UTIs. Materials and Methods: A total of 100 UPEC strains were collected from patients with UTIs in a hospital inTehran in 2016 and diagnosed by biochemical tests and the ability of biofilm formation was determined by Tissue Culture Plate (TCP), tube method (TM) and Congo red agar (CRA) methods. Sensitivity and specificity of methods were determined. Results: In tube method, 23% of the isolates formed strong and 59% formed weak biofilm. In Tissue Culture Plate method 40%, 22% and 28% of isolates formed strong, moderate and weak biofilm respectively and 10% were biofilm negative. According to the Congo red agar method only 4% of the isolates formed strong biofilm, 65% and 31% respectively had a weak biofilm and no biofilm. The sensitivity and specificity of Congo red agar and Tube methods were 39.1%, 50.9% and their features were 78.3%, 79.7% respectively. Conclusions: The results showed that Tissue Culture Plate method is important for the determination of UPEC biofilm formation. Tube method and Congo red agar are not reliable methods for this purpose.

Keywords

• Uropathogenic Escherichia coli
• Biofilm formation
• Phenotypic methods