Development of an improved colonization system for human-derived Bifidobacterium longum subsp. longum in conventional mice through the feeding of raffinose or 1-kestose.

How bifidobacteria colonize and survive in the intestine is not fully understood. The administration of bifidobacteria to conventional mice can be used to evaluate their ability to colonize the intestine in the presence of endogenous gut microbiota. However, human-derived bifidobacteria do not readily colonize the intestines of conventional mice, and although colonization by Bifidobacterium breve UCC2003 has been achieved, the viability of such populations requires improvement. Therefore, we aimed to establish a colonization system with human-derived bifidobacteria of high viability in conventional mice using Bifidobacterium longum subsp. longum 105-A. Lactose, raffinose, and 1-kestose were identified as the preferred carbohydrate sources for the growth of this strain in culture. The administration of B. longum 105-A to conventional BALB/c mice fed these carbohydrates showed that diets containing 6% (w/w) raffinose or 1-kestose facilitated colonization with >10⁸ colony-forming units/g feces for 2 weeks. The population of this strain was more stable in the raffinose-fed group than in the 1-kestose-fed group. The ingestion of these prebiotics had a greater impact on the composition of the microbiota than the administration of B. longum 105-A. The ingestion of these prebiotics also increased the fecal concentrations of organic acids, which was indicative of greater intestinal fermentation. Collectively, we established a colonization system for B. longum 105-A with high viability in conventional mice by feeding the mice raffinose or 1-kestose. This system should be useful for elucidation of the mechanisms of colonization and survival of bifidobacteria in the intestines in the presence of the endogenous gut microbiota.