Correlation of Mutans Streptococci Bacteriocin Genes to Children’s Caries Status

Purpose: to assess whether single or combinations of three novel antimicrobial peptide genes (NN2, PNS1, TKS1) of mutans Streptococci (MS) were associated with dental caries in 2-5 year old children.Methods: Eighty-two caries-free (CF) and 37 severe early-childhood caries (S-ECC) 2-5 year-old children were recruited in a pilot and current studies. Caries status was recorded utilizing the International Caries Detection and Assessment System. Oral MS levels were enumerated from oral swab by selective culture. In the pilot study, MS were isolated from each subject with the genes identified by high-throughput illumina sequencing. In the current study, the genes were identified by SYBR green qPCR assays. The prevalence of the single gene or gene combinations were compared by Chi Square test/Fisher’s exact test between CF and S-ECC group and Odds Ratios were calculated. LogMS levels and decayed surfaces in subjects with or without the single gene or combination of the genes were compared by Student t and non-parametric tests.Results: Thirty-nine CF and 36 S-ECC subjects had MS infection. The prevalence of any of the three genes was 21% in CF and 58% in S-ECC. In the individual gene analysis, PNS1 was the most commonly detected gene (38%) and was significantly more prevalent in S-ECC than in the CF group while NN2 and TKS1 were less prevalent (16% and 19% respectively) and showed no statistically significant difference in prevalence between S-ECC and CF groups. In analysis of combinations of any two or all three genes, the prevalence of all gene combinations with PNS1 were significantly higher in the S-ECC group combination (P<0.05) with the highest Odds ratio in PNS1 – TKS1 (9.17). MS levels between subjects with or without any single gene or combinations of genes were not significantly different (P>0.05). However, mean decayed surfaces were significantly higher in the presence of the genes or gene combinations except for NN2+TKS1.Conclusion: PNS1 and combination of PNS1 with NN2 and/or TKS1 may contribute to caries development and risk. Future studies are needed to study the mechanism of these genes’ function to develop tools for caries prediction and prevention