Adhesion of S-fimbriated Escherichia coli to brain glycolipids mediated by sfaA gene-encoded protein of S-fimbriae

In an attempt to further assess the role of S-fimbriae in the pathogenesis of Escherichia coli meningitis, the adherence of E. coli strains with or without S-fimbriae were examined for this study to purified glycolipids using thin layer chromatography overlay assays. Only S-fimbriated E. coli strains bound to sulfatide, seminolipid, galactosyl ceramide, and lactosyl ceramide but not to gangliosides including sialyl neolacto-series and other neutral glycolipids. The binding of S-fimbriated E. coli to sulfatide was temperature dependent (i.e. maximal at 37 °C) and inhibited by S-fimbriae, anti-S- fimbriae, and anti-S-adhesin antibodies as well as by sulfatide, galactosyl ceramide, and lactosyl ceramide. E. coli transformants which lack the sfaA gene from the Sfa gene cluster showed no binding to the glycolipids, while other transformants lacking the adhesin gene sfaS or sfaG or H and mutants obtained by site-directed mutagenesis in the sfaS gene exhibited a similar binding to the glycolipids compared to the parent S-fimbriated strain. A large amount of sulfated glycolipids was demonstrated on brain endothelial cells and the binding of S-fimbriated E. coli to brain endothelial cells was inhibited by these glycolipids. These findings suggest that the binding of S- fimbriated E. coli to brain endothelial cells occurs in part via glycolipids containing terminal Gal(3SO₄)β-1 residues and in part by S-fimbriae protein SfaA. S-adhesin was not involved in the binding of S-fimbriae to these glycolipids.