[Antagonistic effect against "Clostridium perfringens" exerted in the digestive tract of gnotobiotic mice by "Clostridium" strains isolated from the microflora of conventional mice (author's transl)].

Bacterial strains isolated from the digestive tract of conventional mice produced a barrier effect against a strain of Clostridium perfringens type A (strain CP) in the gastrointestinal tract of gnotobiotic mice. This barrier effect was observed when mice, monoassociated with Escherichia coli K12, were inoculated with a mixed culture of fusiform-shaped clostridia. The collection of fusiforms (collection D) was obtained from a single colony chosen from among the 26 types studied. Collection D and E. coli K12 together exerted a barrier effect against all strains of C. perfringens type A tested. No effect was observed against a C. perfringens type C strain. The expression of the barrier effect depended on the order in which the strains were used to inoculate the mice. Thus strain CP was eliminated from the digestive tract when the mice had previously been associated with collection D and E. coli K12. If the mice were inoculated with strain CP first, however, the barrier effect was only partial. We have also been able to use two strains of clostridia (C1, C3) instead of E. coli K12 to produce a drastic barrier effect against strain CP. The order in which the strains were used to inoculate the mice did not, in this case, influence the production of a barrier effect. Three strains (Da, Db, Dc) isolated from collection D, produced only a partial barrier effect against strain CP in mice previously associated with E. coli K12. These results illustrate the difficulties encountered in determining the minimal number of bacterial strains involved in the production of a barrier effect.