**8. Conclusion**

Apart from possessing virulence factors, for the medical importance of *E. coli* strains the ability to form biofilms is also significant. Biofilms play a major role in urology. Biofilms are namely usually associated with pyelonephritis and chronic or recurrent infections [75]. Biofilm formation is a complex process that may involve multiples adhesins and factors [76]. Biofilm contributes to bacterial resistance [60, 77–81]. Studies have reported that biofilm production mediated by co-expression of curli and cellulose facilitates in *E. coli* helps UPEC to survive in the urinary tract for a long time through the production of an inert, hydrophobic extracellular matrix which surrounds the organism [60, 77, 78].
