Comparison of colonization dynamics and pathology of mice infected with enteropathogenic Escherichia coli, enterohaemorrhagic E. coli and Citrobacter rodentium.

Enteropathogenic Escherichia coli (EPEC), enterohaemorrhagic E. coli (EHEC) and Citrobacter rodentium (CR) colonize the gastrointestinal tract epithelium via attaching and effacing lesions. While humans are believed to be the only living reservoir of typical EPEC and EHEC to have border host specificity, CR is a restricted mouse pathogen. Recently, conflicting conclusions were reported concerning the utility of a murine model to study mechanisms of EPEC and EHEC colonization and infection. We therefore aimed to compare colonization dynamics of EPEC, EHEC and CR, together with a commensal E. coli (Nissle) as a control, in the murine. We show that all strains are equally shed in stools over the first 48 h post inoculation. However, while the CR population then rapidly expanded the EPEC, EHEC and Nissle populations quickly declined to a level just above detection. We conclude that following oral inoculation EPEC and EHEC develop a commensal, rather than pathogenic, interaction within the mouse host.