Colonisation and Translocation of Bacteria in the Intestinal Tract; General Aspects and Studies in a Gnotobiotic Rat Model

Bacterial attachment to surfaces or association to other bacterial species is an important subject for understanding the complex bacterial communities that populate the intestinal tract. Disruption of these ecologically stable communities can lead to harmful effects for the host, i.e. permitting the access of opportunistic or newly arrived pathogens to sterile areas of the body producing disease. Virulence factors present in commensal bacteria can be induced in stress situations and could favour translocation. Different colonisation experiments performed in gnotobiotic rats orally administered with pairs of Escherichia coli isogenic strains differing in a selected virulence factor suggest a role of P fimbriae and K5 capsule in intestinal colonisation. These E. coli traits however, did not favour translocation to mesenteric lymph nodes or other extra-intestinal organs only indirectly by increasing their bacterial numbers in the gut. Gnotobiologic studies are an excellent tool allowing a systemic approach for the study of bacterial traits in colonisation and translocation and should be encouraged for such purposes.