Mutans streptococci in plaque samples from Mongolian mother-child pairs

Objective: Streptococcus mutans and Streptococcus sobrinus are considered to be the principal causative agents of dental caries. The exact age at which their colonization occurs in children is controversial.

The objective of this study was to detect S. mutans and S. sobrinus in Cariostat-inoculated plaque samples of Mongolian mother-child pairs by PCR and to compare their presence with the caries status.

Materials and methods: Oral examination and caries risk assessment using the Cariostat test were carried out on 320 children aged 6-30 months and their mothers. The presence of S. mutans and S. sobrinus was checked by PCR.

Results: 28% of the 6-18-months old children of high-risk mothers and 53.1% of the 19-30-months old children of high-risk mothers had high caries risk (p<0.001). In mothers, the prevalence of S. mutans and S. sobrinus was 79% and 33%, respectively; 54% harbored S. mutans alone, 8% harbored S. sobrinus alone, 25% harbored both strains. In children, 45% were positive for S. mutans alone, 9% were positive for S. sobrinus alone, 18% were positive for both strains. Either or both strains were detected in 67.3% of 6-18-months old children and 76.5% of 19-30-months old children. The caries prevalence of the children aged 6-18 months was 29%, and that of the children aged 19-30 months was 59%. A significant correlation was found between the presence of S. mutans or both strains in mothers and the high-risk children (p<0.05). Moreover, a statistically significant correlation was seen between the presence of S. mutans or both strains in mothers and the caries incidence of their children (p<0.001).

Conclusion: our results showed that mutans streptococci colonization increased with increasing age, so that by 30 months of age, 76.5% of children harbored the bacteria. These data would be relevant for preventive strategies of early chidhood caries.