[Effect of the ingestion of wheat bran on the fecal microbial flora of human donors and of recipient gnotoxenic mice, and on the barrier effects exerted by these flora against various potentially pathogenic microorganisms].

The effect of bran ingestion on the flora of the human digestive tract was studied using two methods: quantitative enumeration of various microbial populations of the faecal flora, and a demonstration of the antagonistic effect exerted by the faecal flora against various potentially pathogenic bacteria of the environment. Since this latter study cannot be effected in human subjects, we used a model constituted by axenic mice inoculated with patients' flora. Faecal samples from 3 human donors receiving bran-containing diets were obtained prior to treatment and 30 days thereafter. These faecal samples were inoculated into axenic mice fed a diet with or without bran. The dominant floras of the human donors, before and after bran ingestion, were highly similar. The faecal floras of the gnotoxenic mice resembled those of the donors and no change resulting from the presence of bran in the diet could be observed. The drastic or permissive barrier effects exerted in the gnotoxenic mice by the human donors against Clostridium perfringens, Staphylococcus aureus, Candida albicans and Pseudomonas aeruginosa were not modified by the presence of bran in the diet. The large variability between animals in the barrier effect against Clostridium difficile masked any possible role of the bran. Study of the transit of Bacillus spores in the digestive tract of various mouse groups showed the existence of differences according to the origin of the inoculated floras, but not according to the presence or absence of bran in the diet.