Unidentified serogroups of enteropathogenic Escherichia coli (EPEC) associated with diarrhoea in infants in Londrina, Parana, Brazil.

Digoxigenin-labelled DNA probes were used to characterise enteropathogenic Escherichia coli (EPEC) isolated in Londrina (Brazil) from faeces samples of 102 children with diarrhoea, and the results were compared with those obtained by serogrouping and adherence to HEp-2 cells. The probes employed detect the gene coding EPEC adherence factor (EAF) and the virulence genes for bundle-forming pilus (bfp) and entero-attaching-effacing (eae) factor. Twenty-one isolates hybridised with at least one probe, and 11 of them were classified as typical EPEC because they hybridised with all three probes, showed a pattern of localised adherence (LA) and carried no genes for enterotoxins (ST and LT) or invasion as detected by PCR. Six of the typical EPEC strains belonged to the classical serotype 0119:H6 and one to O111:H6; O antigens could not be determined in four strains with antisera against 01-0173. All typical EPEC strains carried a 70-MDa plasmid plus two other large plasmids. These data showed that typical EPEC virulence traits may be found in strains not belonging to classical serogroups/serotypes and that molecular identification is required for studying the epidemiology of diarrhoea in children.