Plasmid-mediated factors conferring diffuse and localized adherence of enteropathogenic Escherichia coli

Abstract

Histopathological evidence suggests that the adherence of enteropathogenic E. coli (EPEC) to the mucosa of the small bowel is an important step in pathogenesis. Several reports have shown that many EPEC isolates adhere to HEp-2 and HeLa cells in tissue cultures. In the HeLa cell assay, there are at least 2 distinct patterns of adherence: localized adherence, which is characterized by the formation of bacterial microcolonies, and diffuse adherence, in which bacteria cover the cell uniformly. That these 2 patterns can be demonstrated in HEp-2 cells and in HeLa cells, and that the results of the 2 assays are closely correlated are demonstrated here. Using a DNA probe which is sensitive and specific for localized adherence to HEp-2 cells evidence is provided that localized adherence and diffuse adherence by EPEC are due to at least 2 genetically distinct adhesins which confer phenotypic differences in both the morphology of HEp-2 cell adherence and in surface hydrophobicity. The 2 factors are each encoded on plasmids which vary in size from 55-70 megadaltons; 1 strain exhibiting localized adherence carried these genes on the chromosome.