Production of the Escherichia coli Common Pilus by Uropathogenic E. coli Is Associated with Adherence to HeLa and HTB-4 Cells and Invasion of Mouse Bladder Urothelium

Uropathogenic Escherichia coli (UPEC) strains cause urinary tract infections and employ type 1 and P pili in colonization of the bladder and kidney, respectively. Most intestinal and extra-intestinal E. coli strains produce a pilus called E. coli common pilus (ECP) involved in cell adherence and biofilm formation. However, the contribution of ECP to the interaction of UPEC with uroepithelial cells remains to be elucidated. Here, we report that prototypic UPEC strains CFT073 and F11 mutated in the major pilin structural gene ecpA are significantly deficient in adherence to cultured HeLa (cervix) and HTB-4 (bladder) epithelial cells in vitro as compared to their parental strains. Complementation of the ecpA mutant restored adherence to wild-type levels. UPEC strains produce ECP upon growth in Luria-Bertani broth or DMEM tissue culture medium preferentially at 26°C, during incubation with cultured epithelial cells in vitro at 37°C, and upon colonization of mouse bladder urothelium ex vivo. ECP was demonstrated on and inside exfoliated bladder epithelial cells present in the urine of urinary tract infection patients. The ability of the CFT073 ecpA mutant to invade the mouse tissue was significantly reduced. The presence of ECP correlated with the architecture of the biofilms produced by UPEC strains on inert surfaces. These data suggest that ECP can potentially be produced in the bladder environment and contribute to the adhesive and invasive capabilities of UPEC during its interaction with the host bladder. We propose that along with other known adhesins, ECP plays a synergistic role in the multi-step infection of the urinary tract.