变形链球菌表面蛋白V区、P区及C末端遗传多态性与龋病发生关系的研究

目的了解变形链球菌表面蛋白V区、P区及C末端遗传多态性与其粘附性能的关系。方法实验菌株选自本实验室前期工作所获得的粘附力较强和较弱的血清C型变形链球菌临床分离株，提取全菌DNA，经PCR分别扩增表面蛋白V区、P区编码基因spaP—pv(2060～3157bp)、C末端编码基因spaP-c(4003～4851bp)后，用限制性内切酶Alu I进行限制性片段长度多态性分析。结果两组不同粘附力的变形链球菌(血清C型)临床分离株全菌DNA扩增产物spaP—pv经Alu I酶切后，出现了两种基因型a、b。两种基因型在不同粘附力菌株的分布不同(P＜0．05)，a型在低粘附力菌株中的比例高于高粘附力菌株，而b型在高粘附力菌株中的比例高于低粘附力菌株。spaP—C经Alu I酶切后，共呈现两种基因型C、d。d型在高、低粘附力的菌株中各占1例，其分布无统计学差异。结论spaP—pv基因出现变异可能是变链菌临床分离株粘附功能出现差异的原因之一。

Relationship of the Genetic Diversity within the V-region,P-region and C-terminus of Surface Protein of Streptococcus mutans to Dental Caries

OBJECTIVE: To gain an understanding of the relationship between the genetic diversity within the V-region, P-region, C-terminus of surface protein of Streptococcus mutans (serotype c) and their adherent abilities. METHODS: The clinical isolates of S. mutans (serotype c) in two groups with different adherent abilities (cpm>2000, cpm<1000) had been prepared in our experimental laboratory. The genome DNA was extracted, and the spaP-pv (2060-3157 bp) and spaP-c (4003-4851 bp) were amplified by PCR, respectively. Genetic diversity was assessed by restriction fragment-length polymorphism (RFLP) with restriction endonucleases Alu I. RESULTS: (1) Two different patterns of spaP-pv RFLP among strains were revealed after the amplified product being digested with Alu I. The distributions of two genotypes (a and b) in the clinical strains with different adherent abilities differed significantly (P<0.05). The proportion of genotype b in the strains with higher adherent abilities was higher than that in the strains with lower adherent abilities. (2) Two different patterns (c and d) of spaP-c RFLP among strains were also revealed after the spaP-c being digested with Alu I. No statistically significant difference was observed in the distribution of the two genotypes in the clinical strains. CONCLUSION: The genetic diversity within spaP-pv of clinical isolates of S. mutans might be related to the differences of their adherent abilities.