Abstract
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.
