ABSTRACT
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
Subject(s)
Humans , Bacterial Adhesion/physiology , Blood Bactericidal Activity/physiology , HeLa Cells/physiology , Diarrhea, Infantile/blood , Escherichia coli/physiology , Fetal Blood/immunology , Diarrhea, Infantile/etiology , Escherichia coli/classification , Escherichia coli/pathogenicity , Escherichia coli Infections/complications , Escherichia coli Infections/immunology , SerotypingABSTRACT
Adhesion of enteropathogenic Escherichia coli (EPEC) to HeLa cells is inhibited by human colostrum. In the present study we investigated the effect of colostrum on the stability of pMS49, an EPEC adherence plasmid coding for localized adhesion and ampicillin (Ap) resistance. The plasmid was highly stable after serial passage of bacterial cultures in Tryptic Soy Broth containing 67%, 50%, 10% (v/v) or no human colostrum. A few variants (0.4%) with a low adherence were observed regardless of the treatment given. Human colostrum did not enhance their emergence. No bactericidal or bacteriostatic effect of colostrum was observed under the experimental conditions used. A specific process regulating plasmid expression is supposed to occur in EPRC strains, giving rise to variants with a lower concentration of the outher-membrane adherence-related protein and consequently lower adherence ability. This process seems to also occur for Ap-resistance genes coded in the same plasmid