PCR detection of Streptococcus mutans and Streptococcus sobrinus in plaque samples from Mongolian mother-child pairs

Abstract

Early childhood caries results in a considerable burden of pain and suffering as well as poorer general health. Streptococcus mutans (serotypes c , e and f ) and Streptococcus sobrinus (serotype d and g ) are the species closely associated with 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 plaque samples of Mongolian mother-child pairs by PCR and to compare their presence with the caries status. Dental examination and caries risk assessment using the Cariostat ® carried out on 320 children aged 6–30 months and their mothers. The presence of S. mutans and S. sobrinus was checked by PCR. The caries prevalence and DEFT scores of mothers enrolled in the present study were 98% and 11.5±0.7, respectively. In children, the prevalence and deft scores of the 6–18-month-olds were 29% and 1.3±0.2 while those of the 19–30-month-olds were 59% and 3.4±0.4 correspondingly. Twenty nine percent 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). There was a statistically significant correlation between caries risk of 19–30 month-old children and their mothers ( 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. In conclusion, our results showed that S. mutans and/or S. sobrinus first colonized infants’ teeth from 6–18 months, and the colonization increased with increasing age, so that by 30 months of age, 76.5% of children harbored the bacteria.