Resumo

The adherence on the host surfaces is the first step of microbial pathogens interactions and the crucial to infection by Extra-intestinal Escherichia coli (ExPEC). E. coli constantly acquire and lose virulence attributes leading to the emergence of successful new genetic combinations that confer an increased colonization and disseminate capacity. Many hair like extracellular appendages called fimbriae, produced by Gram-negative pathogens mediate specific bacterial attachment to the cell surface and can ability the pathogen to colonize specifics niches. Human sepsis associated-E. coli (SEPEC) express virulence factors that enable them to adhere and survive in the host blood and tissues. Most of SEPEC strains express these virulence factors, however remains unclear the mechanism by which SEPEC adhere to endothelial cells and invade to blood stream. In this way, we analyzed eight SEPEC strains belonging to phylogroups B2, D, B1 and A (serotypes ONT, O2, O99, O19, O17 and O1) for the presence of new putative adhesins involved in D-mannose resistant endothelial cells adherence. Biotinylated endothelial cell proteins were used to identify SEPEC ligands binding to endothelial cells surface proteins. This overlay assay revealed that one SEPEC ligand recognized by endothelial cells. This protein was identified by mass spectrometry analysis as one 18KDa putative adhesin protein belonging to the chaperone-usher fimbriae subclass described to F9 fimbrial adhesin-like in E. coli O157:H7 str. TW14359 and Uropathogenic E. coli (CFT073). Semi-quantitative PCR (RT-PCR) analysis demonstrated expression of this gene in plancktonic culture conditions and in SEPEC interaction with endothelial cells in vitro. A nule mutant strain for this gene (ydeR) exhibited significantly reduced SEPEC adhesiveness (p<0.05) in α-D-mannopyranoside presence, suggesting it could be an important factor on this bacterial pathotype pathogenesis.