Intestinal epithelial barrier: The target for pathogenic Escherichia coli.

Diarrheagenic Escherichia coli strains are included in 9 pathotypes (pathovars) that present different virulence factors responsible for the patomechanism of infections they cause. As all other intestinal pathogens, E. coli exerts a significant effect on intestinal epithelium. To initiate the infection, these microorganisms have evolved countless strategies to subvert the epithelial barrier and efficiently colonize the intestinal epithelium. The barrier function of the intestinal epithelium is achieved by the presence of a tight junction protein network surrounding individual cells around their circumference that links neighboring cells and seals the intracellular space. Pathogenic E. coli strains may impair intestinal epithelial barrier in 3 different pathways: (i) through a direct effect of their virulence factors on tight junctions proteins, (ii) by disrupting host cell actin cytoskeleton that indirectly damages epithelial barrier, and (iii) via stimulation of the secretion of proinflammatory cytokines that directly disrupt epithelial tight junctions or trigger neutrophils migration through intestinal epithelium, thus disrupting the intestinal barrier. Most pathogenic E. coli generates all these 3 pathways concomitantly upon interaction with intestinal epithelium.