Regulation of Citrobacter rodentium colonization: virulence, immune response and microbiota interactions

Citrobacter rodentium is a mouse-specific pathogen commonly used to model infection by human Enteropathogenic Escherichia coli, an important cause of infant diarrhea and mortality worldwide. In the early phase of infection, C. rodentium overcomes competition by the gut microbiota for successful replication. Then, the pathogen uses a type three secretion system (T3SS) to inject effector proteins into intestinal epithelial cells and induce metabolic and inflammatory conditions that promote colonization of the intestinal epithelium. C. rodentium also elicits highly coordinated innate and adaptive immune responses in the gut that regulate pathogen colonization and eradication. In this review, we highlight recent work on the regulation and function of the C. rodentium T3SS, the mechanisms employed by the pathogen to evade competition by the microbiota, and the function of the host immune response against infection.