Biofilm Formation as a Virulence Determinant of Uropathogenic Escherichia coli Dr+ Strains

Urinary tract infections are the most common health problem affecting millions of people each year. Uropathogenic Escherichia coli (UPEC) strains are the major factor causing lower and upper urinary tract infections. UPEC produce several virulence factors among which are surface exposed adhesive organelles (pili/fimbriae) responsible for colonization, invasion and amplification within uroepithelial cells. The virulence of the uropathogenic E. coli Dr(+) IH11128 is associated with Dr fimbriae belonging to the Dr family of adhesins (associated with diarrhea and urinary tract infections) and a DraD protein capping the linear fiber at the bacterial cell surface. In this study we revealed that biofilm development can be another urovirulence determinant allowing pathogenic E. coli Dr(+) to survive within the urinary tract. E. coli strains were grown in rich or minimal media, allowed to adhere to abiotic surfaces and analyzed microscopically by staining of cells with cristal violet. We found that both Dr fimbriae and DraD, exposed at the cell surface in two forms, fimbria-associated or fimbria non-associated, (DraE(+)/DraD(+), DraE(+)/DraD(-) or DraE(-)/DraD(+) E. coli strains) are required for biofilm formation. Additionally, we demonstrated the biofilm formation capacity of E. coli strains deficient in the surface secretion or production of the DraE adhesin.