Molecular identification of enteropathogenic Escherichia coli (EPEC) associated with infant diarrhea in Londrina, Parana, Brazil

In this work, the prevalence of enteropathogenic Escherichia coli (EPEC) in children in Londrina-PR, Brazil, was evaluated by means of digoxigenin-lab elled DNA probes which identify the plasmid responsible for EPEC adherence factor (EAF), and virulence genes for EPEC as bundle-forming pilus (bfp) an d E. coli attaching-effacing factor (eae). In addition, the isolated strain s were serotyped and tested for adherence to HEp-2 cells. From 102 children with diarrhoea, 19 strains hybridized with at least one probe, and eleven of them were identified as typical EPEC because they hybridized with the th ree probes used, showed a localized adherence (LA) pattern, and presented n o genes for enterotoxins (ST and LT) or invasion as detected by PCR. Six of the typical EPEC strains belonged to the classical serotype O119:H6 (43%); in four strains O antigens could not be determined using antisera against O1 to O173, they were all ONT:H7 (29%); one strain belonged to O111:H6. Thr ee strains were classified as atypical EPEC: O26H-, O111:H9 and O119:HNT. S trains O26H(-) and O111:H9 hybridized with the eae probe only and showed lo calized adherence like (LAL) pattern; strain O119:HNT hybridized with the b fp and eae probes, and showed a localized adherence/diffuse adherence (LA/D A) pattern after 6 h. A DA pattern was observed in two strains isolated fro m children with diarrhoea (ONT:H11 and O142:H34), which hybridized with the eae probe. From 46 controls, five strains hybridized with one or two probe s, but none hybridized with all probes or presented the LA pattern. Three s trains with the DA pattern hybridized with the eae probe. No EPEC strain be longing to classical EPEC serotypes was isolated from faeces of control chi ldren.