Abstract:

Objective To probe the  culture conditions and identification method of the fluoride-resistant strain of Streptococcus mutans(S.mutans)　and to provide theoretical basis for identifying fluoride-resistant strain of S.mutans.Methods In the microaerobic conditions(95%N2,5%CO2),the S.mutans UA159 were induced with NaF concentration gradient,and the fluoride-resistant strain of S.mutans was  obtained.The bacteria was confirmed in terms of the phenotype and genotype.16S rDNA cloning identification of this bacteria was done by physiological and biochemical identification and PCR methods. The phenotypic characteristics of the strain was observed.Results In the microaerobic conditions(95%N2,5%CO2), the fluoride-resistant strain was obtained.The phenotypic characteristics observation,physiological and biochemical identification,and the identification of 16S rDNA results showed that this strain possessed fluoride-resistant stability,and the homology of this bacteria with S.mutans UA159 was 100%,and it was confirmed that this strain was the fluoride-resistant strain of S.mutans.Conclusion The culture conditions of fluoride-resistant strain of S.mutans  are microaerobic conditions(95%N2,5%CO2) in the  brain heart infusion(BHI) substrate for 48 h.S.mutans UA159 induced with NaF is identified as  S.mutans UA159-FR.

Key words:  , fluoride-resistant strain；molecular identification；tooth decay；16S rDNA