IL10 and infection: This prompted us in the present study to perorally challenge aged conventional IL-10-/- mice with a pre-existing chronic colitis (serving as experimental model for ulcerative colitis in humans [20]) with C. coli and to subsequently survey the intestinal colonization properties of the pathogen, the clinical outcome of the underlying chronic colitis until four weeks post-infection and potential C. coli induced shifts in the murine gut microbiota composition in addition to bacterial translocation frequencies.