Bifidobacterium animalis strain DN-173 010 hydrolyses bile salts in the gastrointestinal tract of pigs.

BACKGROUND: Bile salt hydrolase (BSH) activity is widespread among ingested bifidobacteria and lactobacilli. It is sometimes considered to be beneficial because of its putative lowering effect on cholesterol absorption and sometimes considered to be deleterious because it may compromise normal fat absorption and even promote the formation of secondary cytotoxic bile acids by the resident intestinal flora. However, the true hydrolysis of bile salts in vivo by ingested living bacteria remains unexplored. The aim of the study was to examine whether or not Bifidobacterium animalis DN-173 010 (used in fermented milks), which demonstrates a BSH activity in vitro, was also active in vivo during its transit in the intestine of pigs. METHODS: Direct measurement of total and unconjugated bile acids reabsorbed into the portal vein was done, before and after the pigs had been treated for 2 weeks with two daily doses of approximately 3.5 x 10(11) colony-forming units of living (6 pigs) or inactivated B. animalis (6 pigs). RESULTS: None of the treatments modified the portal serum concentration of total bile acids over a 6-h postprandial period. Unconjugated bile acids represented up to 44% and 53% of total bile acids after 1 and 2 weeks of treatment with living bacteria, respectively, compared with only 25% (P < 0.05) before treatment or after 1 or 2 weeks of treatment with inactivated bacteria. CONCLUSIONS: Living B. animalis DN-173 010 exhibited a BSH activity in the gastrointestinal tract of pigs, most probably in the small bowel. There was no sign of increased formation of secondary bile acids beyond the hydrolysis reaction.

Food supplementation with milk fermented by Lactobacillus casei DN-114 001 protects suckling rats from rotavirus-associated diarrhea.

Group A rotavirus is the leading cause of diarrhea among children aged 3-36 mo worldwide. Introducing fermented milk products into the infant diet has been proposed for the prevention or treatment of rotavirus diarrhea. The preventive effect of milk fermented by the Lactobacillus casei strain DN-114 001 was studied in a model of germfree suckling rats supplemented daily from d 2 of life and infected with SA11 rotavirus at d 5 (RF group). One group was supplemented with nonfermented milk (RM) and two uninfected groups (CM and CF) received either nonfermented or fermented milk. Frequency and severity of diarrhea were observed. Rats were killed at various times from 0 to 120 h postinfection (p.i.). Bacteria were measured in the intestine, and rotavirus antigens were detected by ELISA in fecal samples and in different parts of the intestine. Histologic observations were made, including vacuolation, morphology of intestinal villi and number of mucin cells. RM rats had diarrhea for 6 d; compared with the CM group, they had alterations of the intestinal mucosa characterized by cellular vacuolation 48 and 72 h p.i. and a lower number of sulfated mucin cells 72 and 96 h p.i. (P: < 0.05). Early supplementation with fermented milk significantly decreased the clinical signs of diarrhea from 24 to 144 h p.i. (P: < 0.05) and prevented rotavirus infection in all sections of the intestine. Histologic lesions of the small intestine were greatly reduced (P: < 0.05) and the number of mucin cells remained unchanged. The data are discussed with respect to the possibility of reducing rotavirus diarrhea in young children by consumption of fermented milk.

Molecular characterization and comparison of 38 virulent and temperate bacteriophages of Streptococcus lactis.

Thirty-three virulent and five temperate phages of Streptococcus lactis and Streptococcus cremoris were differentiated into three groups by DNA homology. A complete lack of DNA homology was demonstrated between the phage groups. Within each group, large parts of the phage genomes were homologous except for a few phages. One group consisted of five temperate and two virulent phages suggesting that virulent phages isolated during abnormal fermentations and temperate phages isolated after induction from lactic streptococcal starter cultures may be related to one another. We observed a good correlation between the grouping of phages by DNA homology and by their protein composition since within the same DNA homology group, the protein composition of a phage exhibited some similarities with that of the other phages of the group. Therefore, the DNA homologies seemed to be located, at least, in the region coding for the structural proteins. By immunoblotting, we confirmed the relatedness between the proteins of the phages belonging to the same DNA homology group. The important host range factor in bacterium-phage interactions appeared to be an unreliable criterion in determining phage taxonomy.