Susceptibility of bifidobacteria to lysozyme as a possible selection criterion for probiotic bifidobacterial strains.

Resistance or susceptibility of bifidobacteria to lysozyme and growth of bifidobacteria in human milk were tested. Susceptible bifidobacterial strains stopped their growth almost immediately after the addition of lysozyme (400 microg/ml), moderately susceptible strains exhibited reduced growth rate, and growth curves of resistant strains were not affected. Strains of human origin were more resistant to lysozyme than animal strains. While strains of B. bifidum grew well in human milk samples, the growth B. animalis strains was inhibited after inoculation to human milk. The resistance to lysozyme seems to be a promising criterion for the selection of new probiotic bifidobacterial strains.

Relationship between the composition of phospholipids and respiratory activity of choline-deficient mutants of Neurospora crassa.

Phosphatidylcholine is one of the most frequent phospholipid components of the inner mitochondrial membrane of Neurospora crassa. Quantitative analysis of phosphlipids of the wild strain of Neurospora crassa and of its two cho mutants showed that these strains did not significantly differ in the content of phosphatidylcholine. Mutants cultivated in a medium without choline contained, as compared with the wild strain, an increased amount of phosphatidylserine and a decreased quantity of phosphatidic acid. Respiratory activity increased and sensitivity to inhibitors of respiration changed. It is likely that the presence of choline in the growth medium exerts a regulatory effect on the cell metabolism of these mutants.

Naturally occurring prebiotic oligosaccharides in poultry feed mixtures.

The presence of raffinose series oligosaccharides (RSO) was determined by an enzymic method in three commercially available chicken feed mixtures. All feed mixtures contained RSO at a concentration of 2.1-2.2%. Soya meal was identified as the exclusive source of RSO. Subsequently, the bifidogenic effect of stachyose (main soya bean RSO) was also assigned on the growth of poultry intestinal bifidobacteria. Bifidobacteria were counted in chicken intestinal tract using cultivation and FISH methods. Four out of 6 bifidobacterial strains tested grew significantly better on stachyose than on glucose. It can be thus concluded that chicken feed mixtures naturally contain prebiotic oligosaccharides in the form of RSO in higher levels (>2%) compared with the concentration (usually up to 1%) recommended for artificially added prebiotics. Our results therefore indicate that there is no reason for the supplementation of chicken feed mixtures with prebiotics with bifidogenic properties.

Survival of bifidobacteria in adult intestinal tract.

The "cocktail" of human origin rifampicin-resistant bifidobacteria (RRBs) and RRBs from commercial products was administrated to 9 volunteers aged from 22 to 46 years and the survival ability in gastrointestinal tract of these strains was determined. Bifidobacteria represented 0-8 % of total anaerobes detected in gastrointestinal tract of volunteers before the administration of probiotic strains. After the administration of probiotics, bifidobacterial counts increased to 16 % of total bacterial counts. RRBs formed 9-44 % of total counts of bifidobacteria. Then, the counts of RRBs decreased at day 7 after administration, and they were not detected after 14 d. In our study, suitable probiotic bifidobacterial strains for human should be chosen on the basic of in vitro test but the results showed that no strain was able to colonize human tract permanently.

Survival of bifidobacteria administered to calves.

Twenty-five bifidobacteria were isolated from feces of calves. Isolates were identified, and their functional properties and antimicrobial activity were determined. From 10 strains with suitable properties rifampicin-resistant mutants (RRBs) were prepared and mixture of RRBs was administered to 2-d-old calves. These strains were identified by sequencing as Bifidobacterium animalis ssp. animalis (6 strains), B. thermophilum (2 strains), B. choerinum (1 strain) and B. longum ssp. suis (1 strain). The control group was without probiotic treatment. Survival ability of administered bifidobacteria was monitored in fecal samples by cultivation on modified TPY agar supplemented with mupirocin, acetic acid, and rifampicin. Administered bifidobacteria survived in gastrointestinal tract of calves for at least 60 d. Other bacteria were also determined after cultivation using fluorescence in situ hybridization (FISH). Bifidobacteria and lactobacilli dominated in fecal microflora. Significantly lower amounts of E. coli and higher amounts of bifidobacteria and total anaerobes were found in the treated group relative to the control group.