Adherence of bacteria to the intestine in sporadic cases of enteropathogenic Escherichia coli-associated diarrhea in infants and young children: a prospective study.

Intimate adherence of bacteria to duodenal enterocytes was demonstrated in a 12-mo-old child with sporadic diarrhea that was associated with an enteropathogenic Escherichia coli (EPEC) of the serogroup O111:K58. Therefore, a prospective study was initiated to determine if identification of EPEC in stools from sporadic cases of diarrhea of longer than 10 days in duration in children under 24 mo of age correlated with E. coli colonization of the proximal small intestine and with binding of bacteria to intestinal epithelial cells. Colonization was determined by culture of duodenal aspirates and enteroadherence by light- and electron-microscopic evaluation of both duodenal and rectal mucosa. Each EPEC isolate was examined for several previously proposed laboratory markers of virulence including alpha-hemolysin production, agglutination of erythrocytes, cell surface hydrophobicity properties, adherence to HEp-2 cells, and Verotoxin production. Ten sporadic cases of EPEC-associated diarrhea, severe enough to require hospitalization in each instance, were present among 105 patients in whom EPEC were identified in stools. Of the 10 cases, 9 were evaluated in more detail. In contrast to the first case, in the prospective study E. coli were cultured from duodenal aspirates in only 1 patient and enteroadherent organisms were not present on careful review of small bowel (0/9) and rectal (0/7) mucosa. Hemolysin production (9 of 10 EPEC strains), mannose-sensitive hemagglutination (7/10), hydrophobic cell surface properties (0/10), adherence to HEp-2 cells (7/10), and production of Verotoxin (0/10) did not distinguish the one enteroadherent EPEC from the nine EPEC strains in which in vivo enteroadherence was not documented. In this study of sporadic cases of EPEC-associated diarrhea in young children, bacterial colonization of the small bowel and enteroadherence in vivo could not routinely be demonstrated. In addition, those laboratory assays of bacterial virulence that were evaluated did not distinguish the adherent strain from nonadherent EPEC strains.