A quantitative and relative increase in intestinal bacteroides in allergic infants in rural Japan.

Recent studies have suggested that intestinal microbiota play a substantial role in the development of allergic diseases during infancy. We analyzed fecal microbiota in 18 Japanese infants with or without allergy at 6 months and 2 years of age using a cell culture technique. Allergy determination was based on doctor-diagnosed allergic diseases and skin prick tests. There were no differences between 9 allergic and 9 non-allergic infants at 6 months of age in the frequencies or counts of 13 genera and yeast-like organisms. Bifidobacterium was dominant in all infants irrespective of allergy status. At 2 years of age, 8 infants were non-allergic and 10 infants were allergic. Allergic infants at 2 years of age had higher counts of Bacteroides and higher ratios of Bacteroides to Bifidobacterium than non-allergic infants. Despite the small population size used in this study, the results support a significant role of Bacteroides in the pathogenesis of allergy during infancy.