Genotypic profiles by AP-PCR of streptococcus mutans in caries-active and caries-free preschoolers

Streptococcus mutans, an acidogenic and aciduric microorganism that colonizes the oral cavity is recognized as the main causal agent of dental caries. Epidemiological studies have shown a strong correlation between the number of S. mutans in the oral cavity and prevalence and incidence of caries. At present, different genotypic and phenotypic methods are known to determine the profiles of settling and epidemiological distribution of S. mutans. The aim of this study was to investigate the profiles of S. mutans isolated from children with and without dental caries by using the AP-PCR (arbitrarily primed polymerase chain reaction) and api-Zym methods. In the AP-PCR method, random DNA segments of the target bacterium are amplified with single primers of arbitrary sequence. The api-Zym system (bioMirieux, Marcy-létoile, France) is a phenotypic micro-method that allows simultaneous detection of 19 enzymatic activities from bacterial inoculum. A transversal observational study was conducted, which finally included 1203- to 5-year-old children (75 with and 45 without dental caries), who attended a preschool institution in Bogota (Colombia). S. mutans was isolated from 15 of the 45 children without dental caries (33.3%) and from 31 of the 75 children with caries (41.33%). In the 46 children, 69 S. mutans isolates were identified: 24 isolates in the 15 children without dental caries and 45 isolates in 31 children with dental caries. With api-Zym system, 36 different phenotypes were detected: 22 in the caries group and 15 in the caries-free group. The phenotype XX was present in both groups. With the AP-PCR method, 27 different fingerprinting profiles were identified: 22 for the caries group and 9 of the healthy group; the two groups of patients shared four of these genomic profiles. In conclusion, the information shows a great diversity in S. mutans genotypes and phenotypes in the population studied.