Oral Microbiome: Streptococcus mutans/Caries Concordant-Discordant Children

Abstract

Dental caries remains the most common chronic disease in children, and the respective etiology is not fully understood. Though <i>Streptococcus mutans</i> is an important factor in the initiation and progression of caries, its presence is not always associated with the disease. The existence of caries discordant populations, in which <i>S. mutans</i> counts do not correlate with caries experience, poses a challenging problem. This study explored the possible correlation of S. <i>mutans</i> and other microorganism levels on caries-associated ecology of caries-concordant and discordant populations. A total of forty-seven children were analyzed in this study and stratified into four clinical groups based on their <i>S. mutans</i> levels in saliva (HS/LS: High/low <i>S. mutans</i>) and caries experience. <i>Streptococcus mutans</i> levels were determined by culture-based selective plating. The salivary microbiome of caries concordant and discordant populations was investigated by 16S rRNA gene sequencing and downstream bioinformatics analysis. The salivary microbial communities significantly clustered based on <i>S. mutans</i> levels and independent of their caries experience. In addition to <i>S. mutans</i> levels, significant differences in the abundance of other species were observed between HS and LS groups. Interestingly, disease-associated species such as <i>Veillonella dispar, Streptococcus</i> spp., and <i>Prevotella</i> spp. were significantly increased in HS groups and may contribute, in combination with <i>S. mutans</i>, to the caries progression. Furthermore, health-associated species exhibited higher abundance in the LS groups, such as <i>Veillonella rogosae, Haemophilus</i> sp., and <i>Alloprevotella</i> spp. but their possible contribution to the caries process remains to be elucidated. This study provides evidence that <i>S. mutans</i> may play a role in shaping the salivary microbial community. Our results highlight that future caries research should consider additional species as health/disease microbial markers in conjunction with <i>S. mutans</i> to improve diagnosis and caries management of the caries-discordant population.