Genetic analyses of Streptococcus mutans and dental caries levels

Objective: The aim of this study was to access the frequency of mutacin genes (I, II, III and IV) and serotypes c, e and f antigenicity in Streptococcus mutans isolates from an adult population with different levels of caries. Methods: A total of 180 S. mutans isolates from women aged 18 to 34 years were evaluated by polymerase chain reaction (PCR), using specific primers for mutacin I/III and II/IV and serotypes c, e and f (Novak et al., 1994; Qi et al., 2001; Shibata et al., 2003). Amplicons were separated by electrophoresis in 1% agarose gel stained by ethidium bromide. The levels of dental caries were measured by the DMFT index, according to the World Health Organization criteria. (WHO, 1997). Results: Among the women studied, only one case of moderate dental caries was registered and it presented no amplified product for mutacin gene. In the remainder, who showed high levels of the disease, the negative amplification for mutacin by PCR was detected in 36% of the isolates and 20% showed positive genotypes for mutacin IV. It must be highlighted that in some cases, the isolates presented more than one mutacin, being the higher proportion (12%) for the combination I/III. The serotypes' rates were 84.2% for the type c and 15.8% for the types c and f. The presence of serotype e has not been identified. Conclusion: The findings of the present study point out to the greater frequency of the serotype c and the mutacin IV in the studied population.