When cultivated in the presence of trypsin, the Ruminococcus gnavus E1 strain, isolated from a human fecal sample, was able to produce an antibacterial substance that accumulated in the supernatant. This substance, called ruminococcin A, was purified to homogeneity by reverse-phase chromatography. It was shown to be a 2,675-Da bacteriocin harboring a lanthionine structure. The utilization of Edman degradation and tandem mass spectrometry techniques, followed by DNA sequencing of part of the structural gene, allowed the identification of 21 amino acid residues. Similarity to other bacteriocins present in sequence libraries strongly suggested that ruminococcin A belonged to class IIA of the lantibiotics. The purified ruminococcin A was active against various pathogenic clostridia and bacteria phylogenetically related to R. gnavus. This is the first report on the characterization of a bacteriocin produced by a strictly anaerobic bacterium from human fecal microbiota.

Purpose: Delayed diarrhea is the most important side effect of irinotecan. The aim of this study was to investigate the role of intestinal microflora on the induction of systemic and intestinal toxicity and diarrhea, studying germ-free and holoxenic mice i.p. injected with irinotecan. Experimental Design: To evaluate the lethal dose, starting with 100 mg/kg/4 d, we treated the holoxenic mice with100, 80, and 60 mg/kg/4 d and germ-free mice with 60, 80,100, and150 mg/ kg/4 d. We recorded the percentage of dead animals, diarrhea, and the epithelial damage to the jejunum, ileum, cecum, and colon at optical and scanning electron microscopy. Results: Germ-free mice were more resistant to irinotecan than the holoxenic group. The lethal dose was between 60 and 80 mg of irinotecan for holoxenic mice and z150 mg for the germ-free. The intestinal damage score was higher in holoxenic than germ-free mice at 100 mg and equally diffuse in the small and large bowel. The damage in germ-free mice was less severe (8 of 40 samples) prevailing in the ileum. The differences were significant for all sites (jejunum, P < 0.001; ileum, P = 0.012; cecum, P = 0.001; colon, P < 0.001). No damage was found in germ-free mice at 60 mg. Diarrhea was present in all 100 and 80 mg holoxenic mice and in 19 of 20 cases at 60 mg whereas it was absent in 60 mg or sporadic in 80 and 100 mg germ-free mice. Conclusions: The intestinal microflora plays a key role in the intestinal toxicity of irinotecan.

An antibacterial substance appeared within 1 day in feces of gnotobiotic rats harboring a human intestinal Peptostreptococcus strain. It disappeared when the rat bile-pancreatic duct was ligatured or when the rats ingested a trypsin inhibitor. Anaerobic cultures of the Peptostreptococcus strain in a medium supplemented with trypsin also exhibited an antibacterial activity, which was also inhibited by the trypsin inhibitor. In vitro the antibacterial substance from both feces and culture medium was active against several gram-positive bacteria, including other Peptostreptococcus spp., potentially pathogenic Clostridium spp. such as C. perfringens, C. difficike, C. butyricum, C. septicum, and C. sordeUlii, Eubacterium spp., Bifidobacterium spp., and BaciUus spp. Whatever the order of inoculation of the strains, a sensitive strain of C. perfringens was eliminated within 1 day from the intestine of rats monoassociated with the Peptostreptococcus strain. These findings demonstrate for the first time that very potent antibacterial substances can be produced through a mechanism involving intestinal bacteria and exocrine pancreatic secretions.

An animal model for Clostridium butyricum necrotizing cecitis has been developed in axenic chickens inoculated orally between 2 and 50 days of life. Cecitis was obtained with two C. butyricum strains isolated from neonatal necrotizing enterocolitis and not with a Clostridium beijerinckii strain from dairy products; the rate of colonization of the intestinal tract by this strain was lower than that obtained with C. butyricum strains. The clinical findings showed a slow gain in body weight. The cecitis lesions were well developed 3 and 4 weeks after oral inoculation, including enlargement with an increase of the cecum weight-body weight ratio, a marked hyperplasia, congestion, inflammatory infiltrate and pneumatosis of the cecal wall and mesentery, hemorrhage in the lamina propria and submucosa, and ulcerations and necrotic areas in the mucosa. By immunofluorescence and electron microscopy, the bacterial cells were located in the cecal lumen and in necrotic areas of the mucosa. The presence of 4% lactose in the diet seemed to be a prerequisite for the development of cecitis in chickens. A gradual rise of fluorescent antibodies in the sera was observed. Howard et al. (6) reported the presence of Clostridium butyricum in the blood of 9 of 10 and in the stools of 6 of 10 newborns with neonatal necrotizing enterocolitis (NNE). The authors concluded that C. butyricum was probably the final step in the pathogenesis of NNE in this group of babies. Since this observation, C. butyricum was recovered from several outbreaks of NNE (10, 16, 25, 26) and also from fecal specimens of healthy babies (5, 25). Various microorganisms, including Escherichia coli, Klebsiella spp., Enterobacter spp., Pseudomonas spp., Salmonella spp., Clostridium perfringens, Clostridium difficile, coronavirus, rotavirus, and enterovirus, were also associated with NNE (8). Attempts to induce NNE with C. butyricum in animals have not been successful. Lawrence et al. (12) reported hemorrhagic enteritis in neonatal monoxenic rats, but failed to reproduce this previous result (11). In the cecum of gnotoxenic chickens monoassociated with various microorganisms, we observed that C. butyricum produced volatile fatty acids and that its establishment was ca. 108 cells per g of the content (29). The purpose of this study was to develop a experimental chicken model for C. butyricum cecitis wherein necrotic lesions and pneumatosis could be induced through oral inoculation with human strains.