Abstract
The association of the pap operon with the CS31A and F17 adhesins was studied with 255 Escherichia coli strains isolated from calves, lambs, or humans with diarrhea. The three classes of PapG adhesin with different receptor binding preferences were also screened. The pap operon was associated with 50 and 36% of human strains that produced CS31A and ovine strains that produced F17, respectively. Among the bovine isolates, the pap operon was detected in 61% of the CS31A-positive isolates and 72% of the strains that produce both CS31A and F17. The class II adhesin gene was present in bovine (20%) and ovine (71%) isolates. Both class II and III adhesins were genetically associated with 36% of the human strains. The highest prevalence of the pap operon was observed among E. coli strains that produce additional adhesins involved in the binding of bacteria to intestinal cells. Among the bovine isolates, the reference strain for CS31A and F17c was found to be positive for the pap operon. Phenotypic and genotypic characterizations were undertaken. Pap(31A) appeared as fine and flexible fimbriae surrounding the bacteria but did not mediate adhesion to calf intestinal villi. Pap(31A) production was optimal with bacteria cultured on minimal growth media and repressed by addition of exogenous leucine. The deduced amino acid sequence of the PapA(31A) structural subunit showed 57 to 97% identity with the different P-related structural subunits produced by E. coli strains isolated from pigs with septicemia or humans with urinary tract infections. None of the three papG allelic variants was detected, but a homologous papG gene was present in the chromosome of strain 31A.
Highlights
P fimbriae are mannose-resistant hemagglutinins detected predominantly at the cell surface of E. coli strains associated with human urinary tract infection (UTI) [25]
In order to investigate the putative association of P-related fimbriae with CS31A and/or F17-related adhesins, 255 E. coli strains isolated from the intestinal contents of calves, lambs, and hospitalized patients were screened for the papC gene
Among the CS31A-positive isolates, the pap operon was detected in 61% of E. coli strains isolated from the intestinal contents of calves with diarrhea and/or septicemia and 50% of strains isolated from human diarrheic stools specimens
Summary
P fimbriae are mannose-resistant hemagglutinins detected predominantly at the cell surface of E. coli strains associated with human urinary tract infection (UTI) [25]. These fimbriae are closely associated with upper urinary tract colonization and pyelonephritis and bind to the kidney vascular endothelium [28]. We demonstrate that a 17.5-kDa protein produced by the 31A reference E. coli strain was a fimbrial structural subunit closely related to those of the Prs-like fimbria F1651 produced by E. coli strains isolated from piglets with septicemia and to P or Prs fimbriae produced by E. coli strains isolated from humans with UTIs
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