Genotypic variability of Streptococcus mutans and caries experience in children

Objective: To analyze if the genotypic diversity of Streptococcus mutans (SM) in school children 6-8 years of Córdoba is correlated with the disease of caries. Method: The dental clinical examination of children was conducted in a well illuminated environment following procedures of unconventional techniques, recording the number of tooth and the condition of dental surfaces, (healthy, carious, with extraction indicated or missed and filled in temporal and permanent dentition). From these data the indexes DMFT, dmft and oral hygiene (OHI) were calculated according to recommendations of the WHO and Löe & Silness, respectively. In samples of stimulated saliva cultivated in Agar Mitis Salivarius (Difco) with 0.28 mg/ml of bacitracin, the CFU of SM was determined. Colonies were identified morphologically and biochemically using the API 20 Strep kit (Bio Merieux). DNA extraction was performed according to the method of Bollet. To determine the serotypes, multiplex PCR amplifications were performed. Results: Individuals with higher DMFT / dmft (10-21 caries) showed a uniform distribution of serotypes c, e and f, highlighting that the presence of serotype f was observed only in children of this group; and the group of children with 1 to 3 caries only serotypes c and e were detected. No relationship between the CFU/mL of SM (<10⁵ and ≥10⁵) and serotype distribution was detected. Conclusion: The clinical condition of the oral health of the studied school population is poor and it is noticed that the distribution of serotype f was observed in children with high caries experience. These results require the need to focus attention on these children and increasing the number of individuals for further study.