Association of oral streptococci community dynamics with severe early childhood caries as assessed by PCR-denaturing gradient gel electrophoresis targeting the rnpB gene.

This study sought to investigate the possible association between the dynamics of oral streptococci community profiles and severe early childhood caries (S-ECC) development, compared with caries-free (CF) controls. Supragingival plaque samples were evaluated from 8-32-month-old children who had previously been assessed for overall profiles of their oral microbial community. Twelve children were in each group. Bacterial genomic DNA was extracted and amplified using rnpB-specific primers for streptococci; the products were then subjected to denaturing gradient gel electrophoresis (DGGE) and sequence analysis. We observed that the mean values for species richness (N) and diversity of oral streptococci (H') were significantly lower in the S-ECC group than in the CF group (N = 1.25 ± 4.14 vs 14.92 ± 2.84; H' = 1.41 ± 0.29 vs 1.64 ± 0.18) at 32  months of age (P < 0.05). Significantly higher detection rates of Streptococcus sanguinis and Streptococcus gordonii were found in the CF group compared with the S-ECC group at 32  months of age (P < 0.05). Cluster analysis of DGGE profiles showed that most of the clusters were constructed from one individual over time. These results suggested that the onset of S-ECC is accompanied by reduced diversity of oral streptococci, that the detection rates of S. sanguinis and S. gordonii have negative correlations with S-ECC; and that there are high levels of intra-individual similarity for the oral streptococci community over time.