Interactions of Escherichia coli strains of non-EPEC serogroups that carry eae and lack the EAF and stx gene sequences with undifferentiated and differentiated intestinal human Caco-2 cells

Escherichia coli strains of non-EPEC serotypes that carry eae and lack the EAF and the Shiga toxin (stx) gene sequences have been found in acute diarrhea. Both the cell association and the cell entry of these strains in human intestinal epithelial cells were studied as a function of cell differentiation and polarization. The eae+/EAF-/stx- non-EPEC E. coli strains invaded undifferentiated Caco-2 cells more efficiently than differentiated cells. In contrast, prototype EPEC strain E2348/69 did not show significative differences from invasion rates of undifferentiated and differentiated cells. The uptake of these strains was greatly enhanced by pretreatment of differentiated Caco-2 cells with EGTA. These results suggest that the eae+/EAF-/stx- non-EPEC E. coli invasion of intestinal cells may be dependent on receptors expressed on the surface of undifferentiated cells and the basolateral pole of differentiated cells.