16S rRNA gene-based metagenomic analysis identifies a novel bacterial co-prevalence pattern in dental caries.

To identify the prevalence of acidogenic and nonacidogenic bacteria in patients with polycaries lesions, and to ascertain caries specific bacterial prevalence in relation to noncaries controls. Total genomic DNA extracted from saliva of three adults and four children from the same family were subjected to 16S rRNA gene sequencing analysis on a next generation sequencer, the PGS-Ion Torrent. Those bacterial genera with read counts > 1000 were considered as significant in each of the subject and used to associate the occurrence with caries. Sequencing analysis indicated a higher prevalence of Streptococcus, Rothia, Granulicatella, Gemella, Actinomyces, Selenomonas, Haemophilus and Veillonella in the caries group relative to controls. While higher prevalence of Streptococcus, Rothia and Granulicatella were observed in all caries samples, the prevalence of others was observable in 29-57% of samples. Interestingly, Rothia and Selenomonas, which are known to occur within anaerobic environments of dentinal caries and subgingival plaque biofilms, were seen in the saliva of these caries patients. Taken together, the study has identified for the first time a unique co-prevalence pattern of bacteria in caries patients that may be explored as distinct caries specific bacterial signature to predict cariogenesis in high-risk primary and mixed dentition age groups.