Enteropathogenic Escherichia coli (EPEC) is the main cause of diarrhea in infants up to one year of age in the majority of the developing countries. In vitro EPEC strains attach to HeLa or HEp-2 cells in a specific pattern called localized adherence (LA), which is correlated with 93% of the EPEC serotypes. In vivo, EPEC strains adhere intimately to cuplike projections of the apical enterocyte membrane causing localized destruction of the microvilli, described as an attaching and effacing lesion.
Purpose: We showed the attaching-effacing lesions and intracellular penetration in the ultrastructural study of the small intestinal cells as well as in the HeLa cell assay by the following EPEC serotypes: O111ab:H2, O119:H6 and O18ab:H14.
Patients and methods: These strains were isolated from the stools of three infants less than 2 years of age with watery diarrhea who were hospitalized for fluid and electrolyte repairment. In the three patients there were severe ultrastructural alterations of the enterocytes mainly shortening and destruction of the microvilli, and formation of cuplike pedestal lesions. There was also penetration of microorganisms into the cytoplasm of the enterocytes in the interior of endocytotic vesicles. The serotypes of EPEC were assayed with HeLa cells showing the formation of pedestals and penetration into the cytoplasm.
Conclusion: The ultrastructural alterations of the small bowel observed in these patients represent an important indication of the possibility of perpetuation of the diarrhea, owing to either a secretory mechanism or malabsorption of the nutrients.