Germfree mice were orally inoculated with representative bacterial species of infant feces singly or in combination at intervals of a week to demonstrate the effect of 5% dietary galactooligosaccharide (GOS) (70% galactosyllactose, 25% lactose, 5% glucose) on the formation of fecal microflora. We determined bacterial numbers, pH, and enzyme activities of fresh feces or cecal contents from animals and in vitro utilization of GOS by each bacterial species. Staphylococcus epidermidis was decreased by colonization by Escherichia coli and Enterococcus faecalis irrespective of GOS. Bacterial number of E. coli was slightly larger in the GOS group than in the control group. E. faecalis decreased after the establishment of Eubacterium aerofaciens and Clostridium paraputrificum in the GOS group. Clostridium perfringens remarkably decreased after the establishment of Bacteroides vulgatus, Eub. aerofaciens and C. paraputrificum in the GOS group but not in the control. Bifidobacterium breve increased about 100-fold in number in the GOS group as compared with the control. The cecal and fecal pH values were lowered in the GOS group of animals compared with those in the control when they were colonized by plural species. Bif. breve showed the most utilization in vitro of galactosyllactose, and B. vulgatus, Eub. aerofaciens, C. paraputrificum, and En. faecalis moderately utilized in vitro the oligosaccharide. Fecal α-galactosidase, β-galactosidase, β-glucosidase, and β-glucuronidase activities were enhanced after the establishment of bacterial species such as E. coli and B. vulgatus mainly in the animals fed GOS. In conclusion GOS was suggested to have effects on the development of the intestinal microflora and the bacterial interaction in newborn infants.

View full abstract

The effects of Bifidobacteria-fermented milk on human urinary mutagenicity, which increases following ingestion of cooked ground beef, and fecal microflora were investigated using ten healthy volunteers. The urinary mutagenicity was determined by means of Ames Salmonella test. The mutagenicity of urine samples after the ingestion of cooked ground beef during the drinking of Bifidobacteria-fermented milk was significantly lower than that of urine samples before and after drinking (p<0.05). Whereas for unfermented milk, a significant difference was found between during and after drinking (p<0.05). Regarding the changes in fecal microflora, administered Bifidobacterium breve strain Yakult and B. bifidum strain Yakult were recovered in the respective quantities 7.65±0.41 and 8.41±0.36 (log₁₀CFU, means±SD/g-feces) during the drinking of Bifidobacteria-fermented milk. A significant increase in Lactobacillus was observed in the subjects during the drinking of Bifidobacteria-fermented milk compared with before and after drinking (p<0.001 and p<0.002, respectively). In addition, a significant decrease in the number of Enterobacteriaceae was observed during drinking for both Bifidobacteria-fermented and unfermented milk (p<0.01). These results suggest that the drinking of Bifidobacteria-fermented milk may be effective in reducing the carcinogenic risk associated with ingestion of cooked ground beef in meal.

View full abstract

Seventy-four strains of Bifidobacterium were isolated from the feces of three strains of experimental rats, F 344/Jcl, Jcl: Wistar and Slc: Wistar, obtained from two different breeders (Japan Clea; Jcl, and Japan SLC; Slc), by using a non-selective medium (BL agar) and a selective medium (BS agar). Species of these isolates were identified by the sugar fermentation test and DNA-DNA hybridization. All of the 45 strains isolated from F344/Jcl and Jcl: Wistar were identified as Bifidobacterium pseudolongum subsp. globosum. On the other hand, all of the 29 the strains obtained from Slc: Wistar were identified B. animalis. Since B. animalis isolated from Slc: Wistar had not grown on the BS agar, an improved selective medium for the isolation and enumeration of Bifidobacterium from experimental rats was developed. TOS medium, used for enumeration of Bifidobacterium in dairy products, was improved by the addition of cephalothin, phosphomycin, sodium propionate and lithium chloride as selective agents, and by correcting pH of the medium. By using this selective medium, the number of Bifidobacterium in the feces of rats was elucidated 10^6-8 per gram.

View full abstract