Short Communication: Caecal Localisation of the Specific Microbiota Resistant to Clostridium difficile Colonisation in Gnotobiotic Mice

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Abstract
An experimental model developed in our laboratory was used for this study, i.e. a minimum microbiota showing resistance to Clostridium difficile colonisation isolated from the gut of the hamster. Only trixenic mice (C indolis, C. cocleatum, Eubacterium sp.) were able to eliminate the target strain C. difficile. With the ‘Swiss rolls’ technique and scanning electron microscopy, it was shown that at each step of colonisation the caecal barrier microbiota was observed in the mucus present on the surface of the caecal mucous membrane and at the openings of the intestinal crypts, but never in the mucus situated inside the crypts. Moreover, some differences in mucus colonisation could be seen related to each colonisation step. In C. difficile monoxenic mice, these bacteria colonised the mucus in the same fashion as did the bacteria responsible for colonisation resistance. The mechanisms of this barrier effect against C. difficile remain unknown, although it may involve competition between C. difficile and the barrier bacterial population either for an energy substrate or for a specific receptor localised on the oligosaccharide chains of the mucin.