The prevalence of virulent clonal strains of mutans streptococci in vivo and co-culture succession of the strains in vitro—Virulence potential of mutans streptococci

Purpose:To examine selected putative virulent properties of mutans streptococci in two groups with different caries activity and to examine co-culture hybridization of the strains in vitro. Methods: A set of strains from caries-free subjects (115) and another set from caries-active subjects (165) were isolated. Each strain was characterized for three virulence determinants. The clinical bacteria were then cocultured by three strains exhibiting the highest levels of virulence. Isolate colonies of last filial generation bacteria were enrichment-incubated and estimated for virulence again. RAPD-PCR and MLEE analyses were processed for parental bacteria and last filial generation one. Results: No difference associated with caries activity of the subjects from whom the isolates originated. Virulent properties of a filial generation strains was not different in the same generation, but was very different from their parent strains. Conclusion: The coexist properties of virulent polyclonal strain of MS may hold in a very general conditional sense in a dental plaque ecosystem in vivo, however, one of the co-culture strains may became dominant and displaced the others as the result of continuous ecological succession in vitro.