Explore the vast range of titles available.

Ursodeoxycholic acid-producing bacteria are of clinical and industrial interest due to the multiple beneficial effects of this bile acid on human health. This work reports the first isolation of 7-epimerizing bacteria from feces of a healthy volunteer, on the basis of their capacity to epimerize the primary bile acid, chenodeoxycholic acid, to ursodeoxycholic acid. Five isolates were found to be active starting from unconjugated chenodeoxycholic acid and its tauro-conjugated homologue, but none of these strains could epimerize the glyco-conjugated form. Biochemical testing and 16S ribosomal DNA sequencing converged to show that all five isolates were closely related to Clostridium baratii (99% sequence similarity), suggesting that this bacterial species could be responsible at least partially, for this bioconversion in the human gut.

Sixteen Lactobacillus fermentum strains were isolated from the fecal microflora of pigs. They were challenged in vivo, in gnotobiotic mice harboring a porcine flora devoid of lactobacilli. Some of the strains were able to colonize the digestive tract of the mice at high population levels, whilst other strains were eliminated. Chromosomal DNA restriction analysis performed on both colonizing (C-type) and non-colonizing (NC-type) strains were analyzed by pulsed-field gel electrophoresis. Strains LEMPL9 (C-type) and LEM1.16A (NC-type) exhibited a high degree of homology. When challenged in mice harboring a simplified anaerobic flora, LEMPL9 was able to colonize the digestive tract of the animals whereas LEM1.16A was again eliminated. Mutagenesis performed on LEM1.16A allowed the isolation of a mutant able to colonize the gut of mice harboring the simplified anaerobic flora or a complex human flora, suggesting that genes involved in colonization process might have been affected to enhance the bacterium's colonization ability.

Sixteen Lactobacillus fermentum strains were isolated from the fecal microflora of pigs. They were challenged in vivo, in gnotobiotic mice harboring a porcine flora devoid of lactobacilli. Some of the strains were able to colonize the digestive tract of the mice at high population levels, whilst other strains were eliminated. Chromosomal DNA restriction analysis performed on both colonizing (C-type) and non-colonizing (NC-type) strains were analyzed by pulsed-field gel electrophoresis. Strains LEMPL9 (C-type) and LEM 1.16A (NC-type) exhibited a high degree or homology. When challenged in mice harboring a simplified anaerobic flora, LEMPL9 was able to colonize the digestive tract of the animals whereas LEM1.16A was again eliminated. Mutagenesis performed on LEM1.16A allowed the isolation of a mutant able to colonize the gut of mice harboring the simplified anaerobic flora or a complex human flora, suggesting that genes involved in colonization process might have been affected to enhance the bacterium's colonization ability.

The effect of erythromycin base was studied on intestinal resistance to colonization of gnotobiotic mice inoculated with a human fecal flora and challenged with six microbial strains potentially pathogenic for immunocompromised patients. Fecal concentrations of erythromycin were >1,000 µg/g in the human donor and in mice. Total intestinal bacterial counts were not significantly different in the human donor and in the recipient mice and were not affected by erythromycin treatment. Strains of various species from the dominant flora (>109 colony-forming units/g) and resistant to >1,000 µg of erythromycin/ml were present before and persisted during treatment. Strains sensitive to such concentrations — particularly all enterobacteria — were eliminated. Treatment did not reduce colonization resistance against Candida albicans, Clostridium perfringens, and erythromycin-sensitive Escherichia coli. It reduced but did not eliminate some colonization resistance against Pseudomonas aeruginosa, Clostridium difficile, and erythromycin-resistant E coli.

Chez les rats qui reçoivent une flore microbienne qui fait disparaître la distension du caecum présente chez les axéniques, mais qui ne metabolise pas les acides biliaires, le pool intestinal et l'excrétion fécale se rapprochent de ceux des rats holoxéniques. La flore microbienne exerce donc une action non spécifique sur le métabolisme des acides biliaires, en modifiant les caractères de la physiologie digestive qui sont liés à la distension caecale des rats axéniques. Chez les rats qui reçoivent un aliment commercial complexe, le pool intestinal et l'excrétion fécale des acides binaires sont plus élevés que chez ceux qui reçoivent un aliment semi-synthétique qui a la même teneur en cholestérol, et la différence entre les excrétions fécales des rats axéniques et celles des rats holoxéniques est plus grande que chez les rats qui reçoivent l'aliment semi-synthétique. Cette plus grande différence est due surtout à une plus grande excrétion fécale d'acides biliaires chez les rats holoxéniques qui reçoivent le régime commercial : elle est donc en rapport avec une modification de la flore microbienne du tractus digestif sous l'action du régime alimentaire. When axenic rats are given a microflora which causes the caecum distension present to disappear but does not metabolize bile acids, the intestinal pools and fecal excretion of bile acids are intermediary between those of axenic and those of holoxenic rats. This flora acts non-specifically on bile acids metabolism by changing the physiological characters related to caecal distension in axenic rats. The intestinal pools and fecal excretion of bile acids are higher in rats given a commercial chow than in those receiving a semi-synthetic feed containing the same amount of cholesterol; the difference between axenic and holoxenic rat fecal excretions is greater than in rats given the semi-synthetic feed. This wider difference is especially due to greater fecal excretion of bile acids in holoxenic rats given the commercial diet; it is thus related to modification of the gut microbial flora due to diet.

When axenic rats are given a microflora which causes the caecum distension present to disappear but does not metabolize bile acids, the intestinal pools and fecal excretion of bile acids are intermediary between those of axenic and those of holoxenic rats. This flora acts non-specifically on bile acids metabolism by changing the physiological characters related to caecal distension in axenic rats. The intestinal pools and fecal excretion of bile acids are higher in rats given a commercial chow than in those receiving a semi-synthetic feed containing the same amount of cholesterol; the difference between axenic and holoxenic rat fecal excretions is greater than in rats given the semi-synthetic feed. This wider difference is especially due to greater fecal excretion of bile acids in holoxenic rats given the commercial diet; it is thus related to modification of the gut microbial flora due to diet.