Investigation of Supragingival Plaque Microbiota in Different Caries Status of Chinese Preschool Children by Denaturing Gradient Gel Electrophoresis

This study aimed to detect differences in the richness of total supragingival plaque microbiota as well as the species composition of oral streptococci involved in the different stages of dental caries. Forty-five plaque samples were collected from caries-moderate (CM, 4 ≤ dmfs ≤ 6), caries-susceptible (CS, dmfs ≥ 10), and age-matched caries-free children separately. Total DNA was isolated directly from each sample, and polymerase chain reaction–denaturing gradient gel electrophoresis (PCR-DGGE) analyses using universal and primers specific for oral streptococci were carried out. Using 16S rDNA PCR-DGGE, 34 different species of bacteria were identified in a culture-independent manner and classified into 11 genera according to phylogenetic analysis. Among them, Mitis group streptococci and Campylobacter, which were present in health status, no longer appeared in caries-susceptible samples. In addition, Capnocytophaga, Burkholderia, and Prevotella were found significantly less frequently in the CS group samples (P < 0.05), while there were no significant differences among the prevalence of Neisseria, Leptotrichia, Haemophilus, Mutans group streptococci, Corynebacterium, and Actinomyces in the three groups. Further DGGE analysis of rnpB gene amplicons obtained with oral streptococci species-specific primers showed that a total of 23 species of oral streptococci were identified. Streptococcus sanguinis, Streptococcus mitis, and Streptococcus oralis showed a significantly higher prevalence in healthy children (P < 0.05), while that of Streptococcus mutans and Streptococcus sobrinus did not vary among the three groups. Overall, these results suggest that supragingival plaque microbiota as a whole undergoes a more complicated shift in the caries process.