Genotypic Characteristics of Mutans Streptococci in High Caries Risk Children

Mutans streptococci (MS) play a role in initiating dental caries. MS-genotypes can be acquired or lost during dental development. Objectives: The goal of this study was to construct a MS genotype library and identify diversity, commonality, and stability of MS genotypes for children in a longitudinal study. Methods: Nineteen high caries risk children had baseline, six and twelve month plaque samples collected from primary and permanent molar teeth. Seven to ten MS isolates were obtained from each sample. DNA was extracted for repetitive extragenic palindromic-polymerase chain reaction (rep-PCR) followed by microfluidics-based DNA amplicon fractionation and characterization using an Agilent 2100 Bioanalyzer. Data analysis was performed with the DiversiLab software (v3.3) using the Pearson Correlation Coefficient method to create DNA fingerprints, dendrograms, and similarity matrices to interpret data. Results: Among the nineteen children, a total of 1052 isolates were analyzed and seventeen genotypes were identified. The representative genotypes were labeled and stored as a web-based standard MS library. Eight children had one genotype, 8 had two genotypes, and 3 had three genotypes at baseline with an average 1.7 genotypes (diversity). At six- and twelve- month follow up, seven children's genotypes were identical (stability), and twelve children acquired new or lost genotypes from baseline. The most prevalent genotype was shared by six children; two secondary genotypes were observed in five children each (commonality). Conclusion: These results demonstrate construction of longitudinal database for genotypic distribution within and between children. MS genotypes were summarized by distinct diversity, commonality, and stability over time in this high caries risk group.

Supported by NIDCR grant #DE016684