Oral Microbiota Development in the First 60 Months: A Longitudinal Study

Childhood is considered crucial in the establishment of future oral microbiota. However, the precise period of oral microbiota development remains unclear. This study aimed to identify the progression of oral microbiota formation in children. We longitudinally investigated the salivary microbiota of 54 children across 13 time points from 1 wk to 60 mo (5 y) old and their parents at 2 time points as a representative sample of the adult microbiota. Using next-generation sequencing, we obtained 10,000 gene sequences of the 16s rRNA V1-V2 region for each sample. The detection rate in children of 110 operational taxonomic units commonly detected in more than 85% of mothers and fathers, defined as the main constituent bacteria, was 25% at 1 wk old, increased to 80% between 6 and 18 mo old, and reached approximately 90% by 36 mo old. Early main constituent bacteria detected at 1 wk old were limited to <i>Streptococcus</i>, <i>Rothia</i>, and <i>Gemella</i>. At 6 to 18 mo old, the detection rates of various main constituent bacteria, including <i>Neisseria</i>, <i>Haemophilus</i>, and <i>Fusobacterium</i>, increased. UniFrac distance analysis showed that the oral microbiota of children approached that of adults at 6 to 18 mo old. In the weighted UniFrac distance index, unlike the unweighted index, there were no significant changes in children between 36 and 60 mo old from adults, and microbiota formation at 60 mo old was sufficiently advanced to be included within the range of adult individual differences. Our findings suggest that the initial 36 mo, particularly the period from 6 to 18 mo old, consists of a time window for oral microbiota maturation. In addition, the development of microbiota during this period may be critical for future oral disease prevention.