Abstract: Objective: To analyse the relationship between genetic polymorphism and its adhesion ability in Streptococcus mutans clinical isolates of surface protein A Uygur high caries and caries-free children. Methods: Uighur children high caries group ( dmft ≥5) and caries-free group ( dmft=0) were performed clinical strains of Streptococcus mutans adhesion test by bacteria adherent method. We selected the adhesion ability of stronger and weaker strains. The genome DNA was extracted, and the spaP-a was amplified by PCR .Genetic diversity was assessed by restriction fragment-length polymorphism(RFLP) with restriction endonucleases Hae Ⅲ. Results: Adhesion ability of high-caries group was stronger than the caries-free group(33.92 8.79%v. s. 27.53 7.45%), the difference was statistically significant (P<0.05). Two different patterns A and B of spaP-a RFLP among strains were revealed after the amplified product was digested with Hae Ⅲ . The distributions of two genotypes (A and B) in the clinical strains with different adherent abilities differed significantly(P<0.05). A genotype was the majority of the high adhesion force group. Genotype B was mostly in the low adhesion of group. The sequencing DNA testified that the specific base mutation would lead to multiple kinds of genotype resulted. Conclusion: Uighur different caries sensitive children of Streptococcus mutans clinical strains spaP - a gene with genetic polymorphism may be one of the reasons for a discrepancy between the its adhesion ability.

Key words: Uyghur children, Streptococcus mutans, A-region of surface protein , Binding ability , Genotype