Inhibition of enteropathogenic Escherichia coli adhesion to HeLa cells by serum of infants with diarrhea and by cord serum

We have studied the effect of serum from infants with diarrhea and of cord serum on the localized adherence of enteropathogenic Escherichia coli (EPEC) to HeLa cells. Serum samples from 16 infants with diarrhea due to EPEC of serotypes O55:H6, O111: H-, O111:H2, O119:H6 and O142:H6 were used. The adherence ability of EPEC strains belonging to serotypes identical to (homologous) or different from (heterologous) those isolated from the infants' feces was highly inhibited by samples of infant serum collected both during the acute phase of the illness and upon discharge from the hospital. These data confirm the development of antibodies against EPEC adhesins and the cross-reaction between different EPEC serotypes. Cord serum inhibited the localized adherence of EPEC strains at different levels according to the serotype of the strain studied. These results suggest that the placental transfer of adhesin-related antibodies does not protect the newborn against EPEC infections, since half of our patients were less than 30 days old

Use of plasmid profiles to differentiate strains withi9n specific serotypes of classical enteropathogenic Escherichia coli

The usefulness of plasmid profile analysis to differentiate strains of enteropathogenic Escherichia coli (EPEC) was evaluated by studying 123 strains of the most prevalent serotypes causing infant diarrhea in the city of Säo Paulo, Brazil, i. e.,0111ab:H-, 0111ab:H2 and 0119:H6. No common profiles were found among strains of distinct serotypes. However, within each serotype, most of the strains were grouped within a few major profiles. More than 68% of the strainsof serotypes 0111ab:H- and 0111ab:H2 were included in 6 and 9 major profiles, respectively. In 0119:H6, abouth 48% of the strainswere included in 3 major profiles. This analysis suggewsts that only a few EPEC clones are causing infant diarrhea in Säo Paulo and revealed that the distribution of serotypes 0111 ab:H- and 0111ab:H2 during the one-year study was at least partly determined by small outbreaks of the most common profiles. We conclude that plasmid profile analysis is very useful to differentiate strasins within specific EPEC serotypes