Effectiveness of Bifidobacterium bifidum in mediating the clinical course of murine rotavirus diarrhea.

Human Bifidobacterium sp strain bifidum (B. bifidum) was administered to BALB/c lactating mice (n = 58) and their litters (n = 327 pups) to evaluate the ingested strain's adherent properties and ability to inhibit murine rotavirus (MRV) infection. ELISA and anaerobic bacteriologic techniques were used to measure MRV shedding and colonization of Bifidobacterium in the small intestine. At 13-16 d gestation, pregnant dams (and their expected litters) were randomly assigned to one of four experimental groups: 1) normal controls; 2) B. bifidum-treated only; 3) MRV-infected only; and 4) B. bifidum-treated + MRV-infected dams and litters. During the acute phase of diarrhea, 80% of small-intestine cultures in B. bifidum-treated litters were positive for the ingested B. bifidum strain compared with 24% of fecal cultures. Examination of tissue cross sections under electron microscopy revealed the ingested B. bifidum strain survived passage through the upper gastrointestinal tract and adhered to the small-intestine epithelium. After the administration of the high dose of virus, diarrhea developed in all pups, but onset was significantly delayed in B. bifidum-treated + MRV-infected litters compared with litters infected with MRV only (p < 0.02). B. bifidum-treated+MRV-infected pups demonstrated a significant reduction in MRV shedding compared with litters challenged with MRV only at d 2 to 10 after inoculation (p < 0.009). More direct studies are needed to assess mechanisms by which this anaerobe can alter the course of MRV infection at the level of gut epithelium.