Escherichia coli S fimbriae do not contribute to intestinal colonization or translocation in the gnotobiotic rat

Escherichia coli S fimbriae, which bind to sialic acid residues, ave a viru lence factor for extraintestinal infection, but also promote binding to int estinal epithelial cells. In this study, we investigated whether S fimbriae would enhance intestinal colonization by E. coli or promote translocation to extraintestinal sites. A mixture of two E. coli isogenic strains both ex pressing type-1 fimbriae but differing in the carriage of S fimbriae (Sfim + and Sfim -) were given perorally to germfree neonatal, infant or adult ra ts. The Sfim + bound better to rat intestinal mucus and epitheial cells. Ho wever, both strains colonized equally well in both the small and large inte stine and their rate of translocation to the mesenteric lymph nodes was sim ilar. Infant rats had higher E. coli levels in the small intestine than adu lt rats, but their translocation rates were lower. This was at least partly due to their milk diet, since weaned infant rats had more translocating ba cteria than infant rats that continued suckling their mother. The results s uggest that S fimbriae, despite binding to intestinal epithelial cells and mucus, do not contribute to either colonization or translocation in the gno tobiotic vat. (C) 2001 Academic Press.