Exploration of bacterial species associated with the salivary microbiome of individuals with a low susceptibility to dental caries

Dental caries is caused by acidogenic plaque microbiota formed on saliva-bathed tooth surfaces, in which multiple organisms act collectively to initiate and expand a cavity. We explored bacterial species associated with the salivary microbiome of individuals with low susceptibility to dental caries. The bacterial composition of saliva from 19 young adults was analyzed using barcoded pyrosequencing of the 16S rRNA gene; we compared 10 caries-experienced (CE) and nine caries-free (CF) individuals. A quantitative PCR assay of saliva from 139 orally healthy adults aged 40-59 years was carried out to confirm the result obtained by pyrosequencing analysis. The microbiomes of CF individuals showed more diverse communities with a significantly greater proportion of the genus Porphyromonas. Among operational taxonomic units (OTUs) corresponding to the genus Porphyromonas, the OTU corresponding to P. pasteri was the most predominant and its relative abundance in CF individuals was significantly greater than in CE individuals (P < 0.001, Wilcoxon rank sum test). A quantitative PCR assay of saliva confirmed that the amounts of P. pasteri were significantly higher in individuals with lower caries experience (filled teeth < 15, n = 67) than in those with higher caries experience (filled teeth ae15, n = 72) (P < 0.001, Student's t test). These results revealed an association between a greater abundance of P. pasteri and lower susceptibility to dental caries. P. pasteri may be a bacterial species that could potentially be used as a marker for maintaining a healthy oral microbiome against dental caries.