PCR detection of Streptococcus mutans and Aggregatibacter actinomycetemcomitans in dental plaque samples from Haitian adolescents.

Streptococcus mutans and Aggregatibacter actinomycetemcomitans are oral pathogens associated with dental caries and periodontitis, respectively. The aim of this study was to determine the colonization of these two microorganisms in the dental plaque of a group of Haitian adolescents using two different polymerase chain reaction (PCR) methods, standard PCR, and quantitative real-time PCR (qPCR) assays. Fifty-four pooled supra-gingival plaque samples and 98 pooled sub-gingival plaque samples were obtained from 104 12- to19-year-old rural-dwelling Haitians. The total genomic DNA of bacteria was isolated from these samples, and all participants also received caries and periodontal examinations. Caries prevalence was 42.2%, and the mean decayed, missing, and filled surface (DMFS) was 2.67 ± 5.3. More than half of the adolescents (53.3%) experienced periodontal pockets (Community Periodontal Index score ≥3). S. mutans was detected in 67.3% by qPCR and 38.8% by PCR of the supra-gingival plaque samples (p < 0.01), and 36.6% by qPCR and 8.1% by PCR of the sub-gingival samples (p < 0.01). A. actinomycetemcomitans was detected in 85.1% by qPCR and 44.0% by PCR of the sub-gingival samples (p < 0.01), but the prevalence was similar, 67.3% by qPCR and 59.2% by PCR, in the supra-gingival plaque samples. Neither age nor gender was significantly correlated to the bacterial colonization. The results demonstrated a moderate-to-high prevalence of S. mutans and A. actinomycetemcomitans in the Haitian adolescent population, and qPCR is more sensitive than standard PCR in field conditions. These findings suggest that qPCR should be considered for field oral epidemiologic studies and may be necessary in investigations having major logistic challenges.

Prospective study of potential sources of Streptococcus mutans transmission in nursery school children.

Transmission of Streptococcus mutans, a major dental caries pathogen, occurs mainly during the first 2.5 years of age. Children appear to acquire S. mutans mostly from their mothers, but few studies have investigated non-familial sources of S. mutans transmission. This study prospectively analysed initial S. mutans oral colonization in 119 children from nursery schools during a 1.5-year period and tracked the transmission from child to child, day-care caregiver to child and mother to child. Children were examined at baseline, when they were 5-13 months of age, and at 6-month intervals for determination of oral levels of S. mutans and development of caries lesions. Levels of S. mutans were also determined in caregivers and mothers. A total of 1392 S. mutans isolates (obtained from children, caregivers and mothers) were genotyped by arbitrarily primed PCR and chromosomal RFLP. Overall, 40.3 % of children were detectably colonized during the study, and levels of S. mutans were significantly associated with the development of caries lesions. Identical S. mutans genotypes were found in four nursery cohorts. No familial relationship existed in three of these cohorts, indicating horizontal transmission. Despite high oral levels of S. mutans identified in most of the caregivers, none of their genotypes matched those identified in the respective children. Only 50 % of children with high levels of S. mutans carried genotypes identified in their mothers. The results support previous evidence indicating that non-familial sources of S. mutans transmission exist, and indicate that this bacterium may be transmitted horizontally between children during the initial phases of S. mutans colonization in nursery environments.