Modification to intestinal glycosidase activities following Bifidobacterium breve C50 oral challenge in C3H mice

The hypothesis that consumption of bifidobacteria increases intestinal bifi dobacteria, decreases pH and changes glycosidase balance was examined in co nventional mice. A commercially available strain of bifidobacteria, Bifidob acterium breve C50, was tracked 2, 4 and 6 h post-challenge through the gas trointestinal tract of mice. One group (naive mice) consumed the strain for the first time. The other mice were accustomed over 15 days to a daily int ake of 10(7)-10(8) cfu/ml. Bifidobacterium breve C50 was not isolated throu ghout the intestine. After a 15 day-intake, a decrease in endogenous bifido bacteria occured, which was not expected in the distal ileum. This suggeste d an inhibitory effect induced by the probiotic strain. Post-challenge, nai ve mice exhibited a fast increase in colonic bifidobacterial counts, wherea s adapted mice showed no increase in colonic bifidobacteria but mucus was a cidified. This contrasted with the overall increase in pH seen post-challen ge in naive mice. In addition, all cecal glycosidases were expressed at a l ower level after a first administration. Only caecal acid galactosidase act ivity decreased post-challenge in adapted mice. In conclusion, data suggest ed how difficult it is to alter intestinal bifidobacteria permanently and t o affect physiological function by feeding bifidobacteria. (C) 1999 Academi c Press.