Inhibitory interactions between normal fecal flora and Clostridium difficile

Clostridium dfJlcile is the etiologic agent of virtually all cases of antimicrobial- associated pseudomembranous colitis and approximately 2tTh of cases of nonspecific colitis or diarrhea without colitis related to antimicrobial administration. Essentially all antimicrobial agents, with the exception of vancomycin and parenteral aminoglycosides, are capable of inducing C. d(/jlcile-associated intestinal disease. These agents may alter the normal bacterial flora of the gastrointestinal tract so as to permit colonization and/or proliferation, and toxin elaboration, by C. dqfficile. The inhibitory activity of I 16 strains of aerobic bacteria (representing 14 genera) and 285 strains ofanaerobic bacteria (representing nine genera) against C. dfficile was examined using two in vitro procedures. Strains of bacteria in the genera Staphylococcus. Pseudomonas, Streptococcus, Bacteroides, Bifidobacterium, and Lactobacillus inhibited the multiplication ofC. dqfflcile. Members of Lactobacillus and group D enterococci displayed the most antagonistic activity. Not all strains of C. dfJlcile were inhibited by an antagonistic bacterium and not all strains of a particular species possessed inhibitory activity. The antagonistic activity of eight strains of C. dfJlcile against nine genera of anaerobic bacteria (79 strains) and seven genera of aerobic bacteria (25 strains) was examined. Only some strains of bacteria in the genera Peptococcus, Peptostreptococcus. and Bacteroides were inhibited by C. dfflcile. For example, four of the I 7 strains of Bacteroidesfragilis and six of the seven strains of Bacteroides thetaiotaomicron were inhibited by C. dqfJlcile. In several instances, however, all strains of bacteria belonging to a particular genus and species were inhibited by C. d�(Jlcile (e.g.. Bacteroides vulgatus, Bacteroides distasonis, and Bacteroides ovatus). The data obtained in this investigation may help to characterize the mechanism that provides the resistance of the gastrointestinal tract to colonization by C. dfficile. A better understanding of interactions between C. dfficile and other elements of the intestinal flora may lead to more efficient therapy, diagnosis and prophylaxis of oolitis and diarrheal disease associated with antimicrobial therapy. Am. J. Clin. Nutr. 33: 2539, 1980.