Genotypic diversity of Streptococcus mutans and Streptococcus sobrinus in 3-4-year-old children with severe caries or without caries.

BACKGROUND.  The genotypic diversity of both Streptococcus mutans and Streptococcus sobrinus in children with different caries experience remains unclear. AIM.  To investigate the genotypic diversity of S. mutans and S. sobrinus in children with severe early childhood caries (SECC) and in caries-free (CF) children. METHODS.  Stimulated saliva of 87 SECC and 91 CF children aged 3-4 years was collected and submitted to cultivation, and MS colonies were enumerated. The genomic fingerprint analysis of S. mutans and S. sobrinus was carried out using AP-PCR. RESULTS.  One to five genotypes of S. mutans were colonized in an oral cavity of SECC and CF children; 85.5% SECC children and 57.9% CF children harboured more than one genotype of S. mutans. One to three genotypes of S. sobrinus were detected from each SECC child; 31.25% SECC children harboured more than one genotype of S. sobrinus. And one genotype was colonized in each CF child. S. mutans isolates from different individuals displayed distinctive DNA fingerprints. CONCLUSIONS.  DNA fingerprints of S. mutans and S. sobrinus isolates from 3- to 4-year-old children displayed genetic polymorphism, and S. mutans has greater genetic diversity than S. sobrinus. SECC children harboured more genotypes of S. mutans and S. sobrinus than CF children.