Attaching-effacing lesions and intracellular penetration in HeLa cells and human duodenal mucosa by two Escherichia coli strains not belonging to the classical enteropathogenic E. coli serogroups.

In the present study, we compared two strains of serotypes O88:H25 and O145:H45 with an enteropathogenic Escherichia coli (EPEC) adherence factor-positive (EAF+) strain of the classic enteropathogenic E. coli serotype O111ab:H2 for their association with HeLa cells and with biopsies of human duodenal mucosa. Both strains not belonging to the classic EPEC serotype showed virulence properties similar to those of the serotype O111ab:H2 strain, i.e., the production of attaching-effacing lesions and intracellular penetration in both systems. These virulence properties associated with the relatively high frequency at which the two serotypes had been detected in infant diarrhea in São Paulo, Brazil (T. A. T. Gomes, M. A. M. Vieira, I. K. Wachsmuth, P. A. Blake, and L. R. Trabulsi, J. Infect. Dis. 160:131-135, 1989) allowed us to suggest that strains of serotypes O88:H25 and O145:H45 should be included in the EAF+ EPEC category.