不同龋敏感者口腔变形链球菌基因型与产酸性之间的关系

Association between genotype and acidogenicity of Streptococcus mutans in subjects with different caries susceptibility

目的：研究不同龋敏感者口腔变形链球菌基因型与产酸性的关系．方法：①随机选取50例24—32岁的高龋、中龋及无龋者，取牙面菌斑样本接种于MS培养基上，每人随机挑取2—5株临床分离株，提取细菌染色体DNA，采用AP—PCR法对不同龋敏感者口腔变形链球菌临床分离株进行基因分型．②以pH0．5为间隔配制pH4．0～7．0系列的，含50mg／L葡萄糖的MS液体培养基，对不同基因型口腔变形链球菌临床分离株进行厌氧培养48h，用精密pH计检测培养基上清液的pH值．结果：①14例高龋个体中有3例为1种基因型，5例有2种基因型，6例有3种基因型；9例中龋个体中有4例为一种基因型，3例有2种基因型，2例有3种基因型；13例无龋个体中有12例为1种基因型，1例有2种基因型．②不同基因型的变形链球菌培养基上清液的pH值进行统计学分析，发现基因型越多的细菌其产酸能力越强．结论：①龋敏感越高的个体其口腔变形链球菌临床分离株基因型越多；②不同基因型的变形链球菌pH值的检测，基因型越多的细菌其产酸能力越强．

AIM ： To study the genotype of Streptococcus mutans isolated from different caries-susceptible subjects and to analyse the association of the genotype with acidogenicity of Streptococcus isolates. METHODS： Plaque samples were obtained from 50 children who were 24 to 32 years old and originally plated onto Mitis- Salivarius- Bacitracin agar. Chromosomal DNA was ex- tracted from the isolates obtained from samples by DNA kit. Then genotyping of Streptococcus mutans was carried out by arbitrarily primed polymerase chain reaction（AP-PCR）. Streptococcus mutans were inoculated in MS media containing 5 mg/L glucose and with different pH values （4.0 ～ 7.0） ,and grew in anaerobic condition （ 80 mL/LN2, 100 mL/LH2,100 mL/LCO2 ） at 37℃ for 48 h. The final pH values of the solutions were measured, and then compared. RESULTS： Isolates of Streptococcus mutans were obtained from 36 subjects （total 50 subjects）. 101 Streptococcus mutans strains were obtained and 31 genotypes were found. More than one genotype isolates were colonized in the same individual of 14 high-caries subjects,6 possessed three genotypes,5 possessed two genotypes,and 3 had one genotype; of 9 middle-caries subjects,2 possessed three genotypes,3 possessed two genotypes,and 4 had one genotype;of 13 caries free subjects , 12 had one genotype, 1 possessed two genotypes. Statistical analysis of the final pH values of culture supernatants revealed that the isolates with more genotypes presented the stronger ability of acidogenicity. CONCLUSION： AP-PCR technology can obtain genetic map of Streptococcus mutans. There are more genotypes and the higher acidogenicity of Streptococcus mutans isolates in the high-caries subjects than in the middle-caries and caries-free ones.