Development and establishment of oral microbiota in early life

The oral microbiota has recently attracted attention owing to its association with oral and systemic diseases. Accordingly, gaining an understanding of oral microbiota development and the factors influencing it can contribute to preventing the establishment of dysbiotic oral microbiota and, eventually, oral microbiota-related diseases.

In this review, we highlight the results of a longitudinal project focusing on oral microbiota development during early life. At 4 months of age, the oral microbiota of infants was found to differ considerably from the maternal oral microbiota, even though infants acquire oral bacteria from their mothers. At 18 months, although the infant microbiota is still not completely comparable with that of adults, from 4 to 18 months, there is a rapid phase of development, during which the microbial composition undergoes considerable change to a profile more similar to that in adults. During this development, the infant oral microbiota converges into two different profiles with adult-like traits, namely, Streptococcus salivarius- and Neisseria-dominant profiles. This divergence is strongly influenced by dietary habits, with a frequent intake of sweetened beverages being associated with an S. salivarius-dominant profile, which is suspected to be implicated in oral and systemic diseases.

The foundation of the adult oral microbiota may be established by 18 months of age, and the developmental period from 4 to 18 months may be an appropriate period during which to modify the microbial balance to obtain a desirable healthy state. In particular, dietary habits during this period warrant close attention.