Signatures in the gut microbiota of Japanese infants who developed food allergies in early childhood.

Bacterial colonization in infancy is considered crucial for the development of the immune system. Recently, there has been a drastic increase in childhood allergies in Japan. Therefore, we conducted a prospective study with 56 infants on the relationship between gut microbiota in the first year of life and the development of allergies during the first 3 years. In the lactation period, organic acid producers such as Leuconostoc, Weissella and Veillonella tended to be underrepresented in subjects who developed food allergies (FA, n = 14) within the first two years. In the weaning period, children in the FA group were highly colonized by unclassified Enterobacteriaceae and two Clostridium species closely related to Clostridium paraputrificum and C. tertium, and the whole tree phylogenetic diversity index was significantly lower in the FA group. All of these differences in the weaning period were statistically significant, even after adjusting for potential confounding factors. A higher abundance of unclassified Enterobacteriaceae was also found in the other allergic group (n = 15), whereas the two Clostridium species were highly specific to the FA group. The mode of action of these Clostridium species in childhood food allergies remains unknown, warranting further investigation.