CECAL LOCALIZATION OF THE SPECIFIC MICROBIOTA RESISTANT TO CLOSTRIDIUM-DIFFICILE COLONIZATION IN GNOTOBIOTIC MICE

An experimental model developed in our laboratory was used for this st udy, i.e. a minimum microbiota showing resistance to Clostridium diffi cile colonisation isolated from the gut of the hamster. Only trixenic mice (C. indolis, C. cocleatum, Eubacterium sp.) were able to eliminat e the target strain C. difficile. With the 'Swiss rolls' technique and scanning electron microscopy, it was shown that at each step of colon isation the caecal barrier microbiota was observed in the mucus presen t on the surface of the caecal mucous membrane and at the openings of the intestinal crypts, but never in the mucus situated inside the cryp ts. Moreover, some differences in mucus colonisation could be seen rel ated to each colonisation step. In C. difficile monoxenic mice, these bacteria colonised the mucus in the same fashion as did the bacteria r esponsible for colonisation resistance. The mechanisms of this barrier effect against C. difficile remain unknown, although it may involve c ompetition between C. difficile and the barrier bacterial population e ither for an energy substrate or for a specific receptor localised on the oligosaccharide chains of the mucin.