A new selective medium for the isolation of glucose non-fermenting bifidobacteria from hen caeca

Detection of infant faecal bifidobacteria by enzymatic methods

An enzyme-based assay was developed for the detection of bifidobacteria in infant faeces. Ninety-five samples from 51 breast-fed infants in the age between 3 and 276 days were investigated. Bifidobacteria and other bacterial groups were determined by cultivation and fluorescence in situ hybridisation (FISH). Faecal samples were examined for the activity of fructoso-6-phosphate phosphoketolase (F6PPK) and for other enzymatic reactions using the API-ZYM kit. Twenty-nine infants had high numbers of bifidobacteria (usually higher than 9 log CFU/g) in their faeces. Seventeen infants (35%) did not contain detectable amounts of bifidobacteria in their faecal samples. The remaining five individuals had low counts of bifidobacteria (3-6 log CFU/g). Most negative infants possessed major amounts of clostridia in their faecal flora. There were no significant differences among bifidobacterial counts obtained by cultivation and FISH, detection of F6PPK, alpha-galactosidase and alpha-glucosidase activities could routinely be used for the rapid and simple detection of bifidobacteria in infant faecal samples. Bifidobacterial colonies were identified using enzymatic tests and PCR procedure based on 16S rRNA gene sequences species-specific primers. In 14 samples, the identifications of individual isolates were compared with direct analyses of faeces using the nested PCR-denaturing gradient gel electrophoresis (nested DGGE) procedure. The results obtained in several cases are not identical. Bifidobacterium longum and Bifidobacterium breve were most frequently identified. Bifidobacteria-positive samples had high activities of alpha-galactosidase and alpha-glucosidase. On the contrary, negative samples missed either one or both of these enzymatic activities. While all positive samples tested showed distinctive fructose-6-phosphate phosphoketolase activity (F6PPK), none of the negative samples expressed F6PPK activity.

The bifidogenic effect of Taraxacum officinale root

The infusion of dandelion root (Taraxacum officinale) stimulated in vitro the growth of 14 strains of bifidobacteria. The utilization of oligofructans, glucose, fructose and total saccharides was determined by enzymatic and phenol-sulfuric methods. Dandelion oligofructans were important source of carbon and energy for bifidobacteria tested.

Short fractions of oligofructose are preferentially metabolized by Bifidobacterium animalis DN-173 010

The growth of Bifidobacterium animalis DN-173 010 on different energy sources was studied through small- and large-scale fermentations. Growth on both more common energy sources (glucose, fructose, galactose, lactose, and sucrose) and inulin-type fructans was examined. High-performance liquid chromatography analysis was used to investigate the kinetics. Gas chromatography was used to determine the fructan degradation during the fermentation process. B. animalis DN-173 010 was unable to grow on a medium containing glucose as the sole energy source. In general, monosaccharides were poor growth substrates for the B. animalis strain. The fermentations with the inulin-type fructans resulted in changes in both growth and metabolite production due to the preferential metabolism of certain fructans, especially the short-chain oligomers. Only after depletion of the shorter chains were the larger fractions also metabolized, although to a lesser extent. Acetic acid was the major metabolite produced during all fermentation experiments. At the beginning of the fermentation, high levels of lactic acid were produced, which were partially replaced by formic acid at later stages. This suggests a shift in sugar metabolism to gain additional ATP that is necessary for growth on oligofructose, which is metabolized more slowly.

Enumeration, isolation, and identification of bifidobacteria from infant feces

Thirty-three fully breast-fed infants aged between 1 and 12 weeks were screened for bifidobacteria in feces. Bifidobacteria counts in most fecal samples determined both by TPY agar and FISH procedure ranged from 10(8) to 10(11) CFU/g. Three infants did not contain any bifidobacteria in their fecal samples. One child was delivered by caesarean section and the other two by normal vaginal delivery. All bifidobacteria-free infants possessed Gram-positive regular rods as a major group of their fecal flora. These bacteria were identified as clostridia using genus-specific FISH probe. In bifidobacteria-positive samples, B. longum (57.9% of the samples) was the most frequently found species, followed by B. adolescentis (31.6%), B. bifidum (21.0%), B. breve (10.5%), B. pseudocatenulatum (5.3%), and B. dentium (5.3%).