Objective: To examine the prevalence of five oral streptococci species of severe early childhood caries (S-ECC) and caries-free (CF) groups. Study design: Supra gingival plaque samples were obtained from 198 Thai children with ages ranging from one to six years old. Eighty-seven subjects had no caries (dmft=0), and 111 had S-ECC. After DNA extraction, S. mutans, S. sobrinus, S. sanguinis, S. oralis, and S. gordonii were identified by standard PCR using species-specific primers. Statistical analysis determined the differences among prevalence rates of each species using Pearson chi-square test. The relationship among dmft score, age, sex and caries status within each group was analyzed by logistical regression (p ≤ 0.05). Results: Sex was not correlated with any of the species detected in both groups (mean age =3.09, mean±SD of dmft=11.04±7.89). S. mutans was found at greatest prevalence in both groups followed by S. oralis. S. gordonii was detected at a high prevalence, but S. sobrinus and S. sanguinis were lower in S-ECC when compared with those from the CF group. Conclusion: S. mutans was associated significantly with S-ECC (p ≤ 0.05). Caries prevalence was highest (56.5%) in subjects infected by S. mutans alone. S. sanguinis prevalence was higher in the CF group, but not statiscally different. Infection with MS did not show higher caries prevalence.
Nested PCR gave a higher detection frequency than standard PCR but not significant (p ≤ 0.05). The prevalence of S. mutans was not different between the two groups, while the prevalence of L. fermentum was significantly associated with S-ECC (p ≤ 0.05).
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