Development of the oral micro biome during childhood: an ecological succession associated with dental health status

Information on how the oral microbiome develops during early childhood and how external factors influence this process is scarce. In the current study, we used high-throughput sequencing to characterise bacterial composition and diversity in saliva samples collected at 3, 6, 12, 24 months and 7 years of age in 90 longitudinally followed children, for whom clinical, dietary and health data were collected. Bacterial diversity and richness increased steadily from birth throughout childhood. Bacterial composition patterns changed through time, starting with “early colonizers” associated with the initial breastfeeding period, including Streptococcus and Veillonella. Other bacterial genera such as Neisseria and Actinomyces settled after one or two years of age. Caries development at 9 years of age was associated with diverging microbial composition through time. Streptococcus cristatus appeared to be associated with increased risk of developing tooth decay and its role as an etiological factor and as potential biomarker of the disease should be further studied. Infants born by C-section had initially skewed bacterial content compared to vaginally delivered infants, but this was recovered with age. However, shorter breastfeeding habits and antibiotic treatment during the first 2 years of age were both associated with a different bacterial composition at later age. Taken together, the data are consistent with oral microbiota development being an ecological succession. Thus, an altered colonization pattern during the first year of life may have long-term consequences for oral microbiome development, whose potential impact on the child's oral and systemic health should be further studied.