Background. Epidemiological studies point to the gut as a key reservoir of multidrug resistant E. coli ST131, a globally dominant pathogenic clone causing urinary tract and bloodstream infections. Here we report a detailed investigation of its intestinal lifestyle.
Methods. Clinical ST131 isolates and type 1 fimbriae null mutants were assessed for colonisation of human intestinal epithelia and in mouse intestinal colonisation models. Mouse gut tissue was examined by histology for pathology and ST131 localisation. Key findings were corroborated in mucus-producing human cell lines and intestinal biopsies.
Results. ST131 strains adhered to and invaded into human intestinal epithelial cells more than probiotic and commensal strains. The reference ST131 strain EC958 established persistent intestinal colonisation in mice and expression of type 1 fimbriae mediated higher colonisation levels. Bacterial loads were highest in the distal parts of the mouse intestine and did not cause any obvious pathology. Further analysis revealed that EC958 could bind to both mucus and underlying human intestinal epithelia.
Conclusions. ST131 strains can efficiently colonise the mammalian gut and persist long-term. Type 1 fimbriae enhance ST131 intestinal colonisation suggesting that mannosides, currently developed as therapeutics for bladder infections and Crohn’s disease, could also be used to limit intestinal ST131 reservoirs.