Differences in the composition of intestinal Bifidobacterium species and the development of allergic diseases in infants in rural Japan

Background: Bifidobacterium is a dominant genus in the intestinal microbiota of infants and comprises many different species. A series of studies performed in northern Europe showed differences in the composition of Bifidobacterium species between allergic infants and healthy controls. Additional studies are needed to confirm this observation. Objective: To investigate the composition of fecal Bifidobacterium species in allergic infants and healthy controls in Japan, using molecular methods. Methods: Full-term born babies were followed up to 6 months of age at a local hospital in rural Japan. The presence or absence of allergy was determined based on allergic symptoms and skin prick tests. Fecal Bifidobacterium species in allergic infants (n=10), and healthy controls (n=16) were evaluated using nine Bifidobacterium species-specific or group-specific primers based on 16S rDNA sequences at 1, 3, and 6 months of age. Results: The number of the infants in whom no Bifidobacterium species could be found was four (15.4%) at 1 month, two (7.7%) at 3 months, and one (3.3%) at 6 months of age, all of whom were healthy controls. At 1 month of age, allergic infants had a higher prevalence f the Bifidobacterium catenulatum group than healthy controls (60.0% vs. 6.3%, P < 0.01). At 6 months of age, allergic infants had a higher prevalence of B. bifidum than healthy controls (70.0% vs. 12.5%, P < 0.01). These differences were not related to feeding method. Conclusions: Our results in infants in rural Japan support the hypothesis that a compositional difference in intestinal Bifidobacterium species may be associated with the development of allergy in early infancy, although the responsible species might vary among countries or races.