Production of an antibacterial substance in the digestive tract involved in colonization-resistance against Clostridium perfringens.

Ruminococcus gnavus E1, Bacteroides thetaiotaomicron LEMF4, Clostridium hathewayi LEMC7, and Clostridium orbiscindens LEMH9 were isolated from ex germ-free mice inoculated with a human faecal microbiota. When initially germ-free mice who were previously inoculated with the strain E1 alone, or a four-strain consortium [E1, LEMF4, LEMC7, and LEMH9], were then challenged with 10⁸ counts of Clostridium perfringens; the target strain was rapidly eliminated from the digestive tract of the animals (<10² cfu g⁻¹ of faeces). R.

Intestinal microflora and digestive toxicity of irinotecan in mice.

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.

Ruminococcin A, a new lantibiotic produced by a Ruminococcus gnavus strain isolated from human feces.

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.

Trypsin-dependent production of an antibacterial substance by a human Peptostreptococcus strain in gnotobiotic rats and in vitro.

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.

Experimental cecitis in gnotobiotic quails monoassociated with Clostridium butyricum strains isolated from patients with neonatal necrotizing enterocolitis and from healthy newborns.

Using axenic quails fed a diet containing lactose, we have investigated the potentially pathogenic roles of six Clostridium butyricum strains of human origin. Three strains (CB155-3, CB1002, and CB203-1) isolated from neonatal necrotizing enterocolitis patients and two of three strains (CB19-1 and CB25-2) isolated from healthy newborns led to cecal or crop lesions or both similar to those observed in human neonatal necrotizing enterocolitis: thickening of the cecal wall with gas cysts, hemorrhagic ulcerations, and necrotic areas. The lactose-negative strain (CB46-1) did not develop any lesions.