[Intestinal bacterial colonisation and translocation in C3H/HeJ conventional mice fed a unique dose of live or dead Bifidobacterium breve C50]. / Colonisation intestinale et translocation bactérienne chez la souris conventionnelle C3H/HeJ apres ingestion d'une dose unique de Bifidobacterium breve C50 vivantes ou mortes.

The efficiency and safety of use of Bifidobacterium breve C50 (BbC50), a potential probiotic, was assessed as regards intestinal microbial colonisation and bacterial translocation. A suspension of BbC50, containing 1-5 to 107-108 live bacteria, was fed to C3H/HeJ mice. The passage of live BbC50 was not demonstrated by culture either in the intestine or extra-intestinal organs. However, mice receiving the highest dose of live bacteria harbored more lactobacilli and less Bacteroides fragilis group in the cecum and colon when compared to control mice. Translocation of lactobacilli observed in the control group was not regulated by Bb50 feeding. Indeed, the spleen was significantly more frequently contaminated in mice fed BbC50, whatever the dose of live bacteria. The kidneys were also significantly more contaminated with lactobacilli in mice fed the highest dose of live Bb50. Moreover, higher dose of live BbC50 was associated with greater number of extra-intestinal contaminated organs. To conclude, BbC50 feeding induced a favorable balance in the mouse intestinal flora and was never found translocating, demonstrating its efficiency and safety of use. However, BbC50 seemed to interfere with the ability of lymphoid organs (e.g. the spleen) to eliminate translocating lactobacilli.

Partial characterization of bifidobacterium breve C50 cell-free whey compounds inducing modifications to the intestinal microflora.

Cell-free whey obtained from milk fermented with Bifidobacterium breve C50 (Bb C50) has been shown to modify the intestinal flora in humans and mice. Previous work showed that no antibiotic-like or barrier effect due to overgrowing bifidobacteria was implied in the microbial modifications. The present study was focused on characterizing the compounds and mechanisms involved. Protein, sugar, and enzymatic profiles of Bb C50 whey were therefore determined and compared to those of a whey unable to modify the intestinal flora of humans and mice. No remarkable difference was noted except for a higher lactosidase activity in Bb C50 whey. Various physical treatments were then applied to fractions of Bb C50 whey. Activity was assessed in C3H mice by analyzing changes in the intestinal flora balance throughout a 15-d administration of each treated whey. Heating at 80 degrees C and aerobic storage for 2 wk completely abolished Bb C50 whey activities. In contrast, the addition of a reducing agent (cysteine hydrochloride), either at the beginning of a 15-d aerobic storage or prior to administration, as well as preserved these activities. Susceptibility to heating and oxidation suggested that an enzyme might play a role in the induced microbial changes. Since the Bb C50 lactosidase was partly inactivated by the oxidative treatment, it could support the in vivo activity. The enzyme might reach the intestinal lumen and partly degrade substrates, such as mucins, usually used by the intestinal flora. The released molecules might then favor the development of a new microbial balance.

Pseudomonas brenneri sp. nov., a new species isolated from natural mineral waters.

The vernacular name 'fluorescent Pseudomonas group 97-391' was coined for a group of 11 strains isolated from two French natural mineral waters. All these strains were Gram-negative, rod-shaped and motile by means of a single polar flagellum. They produced fluorescent pigment (pyoverdin) on King B medium, catalase and cytochrome oxidase. They were not able to accumulate poly-beta-hydroxybutyrate. They were capable of respiratory but not fermentative metabolism. DNA-DNA hybridization results and DNA base composition analysis revealed that strains of the 'fluorescent Pseudomonas group 97-391' were members of a new species, for which the name Pseudomonas brenneri sp. nov. (type strain CIP 106646T) is proposed. The levels of DNA-DNA relatedness within this group ranged from 70 to 100% with DeltaTm below 1 degree C. The G+C content of the DNA of the type strain was 58 mol%. DNA relatedness with 72 strains representing well-known or partially characterized species of the genus Pseudomonas (sensu stricto) was below 48%. The complete 16S rRNA sequence of the type strain CIP 106646T was determined and compared with those of the type strains of Pseudomonas species. Finally, a phylogenetic tree was inferred from sequence analysis and demonstrated that the new species fell into the 'Pseudomonas fluorescens intrageneric cluster'. The clinical significance of P. brenneri is unknown.

The regulatory effects of whey retentate from bifidobacteria fermented milk on the microbiota of the Simulator of the Human Intestinal Microbial Ecosystem (SHIME).

AIMS: To investigate the effects of whey retentate from Bifidobacteria fermented milk. METHODS AND RESULTS: The simulator of the human intestinal microbial ecosystem (SHIME) was used. The composition of the microbiota and its metabolic activities were analysed. Changes in the microbial composition became apparent within 15 days of the treatment in the vessels representing the ileum and the large intestine. The whey retentate favoured the growth of endogenous bifidobacteria and induced a decrease in Bacteroides fragilis and in sulphite-reducing clostridia, especially Clostridium perfringens. After the administration was stopped, these populations tended to revert to their original levels, except for the streptococci and the staphylococci populations. The treatment also led to an increase in acetic acid, CH4 and CO2 production, suggesting overgrowth of some anaerobic bacteria. Ammonium, generally considered as undesirable, declined. CONCLUSIONS: The whey retentate clearly altered the microbial community in the SHIME. SIGNIFICANCE AND IMPACT OF THE STUDY: Whey retentate appears to exert a beneficial effect on the in vitro gastrointestinal system; these findings warrant confirmation by in vivo studies.

Cell-free wheys from bifidobacteria fermented milks exert a regulatory effect on the intestinal microflora of mice and humans.

Bacteroides fragilis and clostridia are normally present in the human colon but they may exert pathogenic effects when the homeostasis is upset following various forms of stress. One approach to preventing gastrointestinal disorders is to use bifidobacteria fermented milk. It has been suggested that the efficacy of such a product is related to abiotic compounds produced during milk fermentation. Experiments reported in this paper attempt to check this theory. Six whey retentates were prepared by fermenting cow's milk with six human strains of Bifidobacterium breve and acetic and lactic acids were eliminated by ultrafiltration. Their ability to reduce intestinal clostridial carriage was assessed in C3H mice. Only one whey retentate led to a decrease in clostridia, bacilli, B. fragilis and fecal pH and to an increase in bifidobacteria. Assays in ten human volunteers resulted in similar changes in fecal flora and fecal pH within 7 days of whey retentate intake (30 mL/day). No antibiotic-like effect was demonstrated in vitro. Compounds involved in microflora regulation were located in two ultrafiltrated fractions (30-100 and 100-300 kDa). Both fractions contained mainly low molecular weight glycoproteins (20-40 kDa) and two high molecular weight glycoproteins (121, 211 kDa) that were almost undetectable in the inactive 10-30 kDa fraction.