不同龋敏感儿童口腔不同基因型变异链球菌临床分离株在不同pH条件下产生GTF能力的比较研究

摘要

AIM:To investigate the glucosyltransferase (GTF) activity of Streptococcus mutans (S.mutans) with different genotype isolated from children with different caries experience under different pH conditions.METHODS:66 strains of S.mutaus isolated from dental plaques of children with different caries experience were cultured.Bacterial suspension was adjusted to A540 nm=1.0,then 100 μL of the suspension was inoculated to 10 mL TYC at different pH ranging from 5.0 to 7.0 containing 0.25％ (w/v) glucose and 0.05％ (w/v) Tween80 respectively for 18 h at 37 ℃.Somogyi method was used to measure GTF activity.RESULTS:There were significant differences in GTF activity among the strains isolated from children with different caries susceptibility in the same pH value (P ＜ 0.05),higher GTF activity was produced by the strain with higher cariogenecity and higher GTF activity was found in the strain with more genotypes.GTF activity of a genotype strain decreased with the decrease of pH value from 7 to 5.CONCLUSION:The S.mutans strain with more genotypes has higher GTF activity and higher cariogenecity.%目的:探讨不同龋敏感儿童口腔变异链球菌不同基因型菌株在不同pH条件下产生GTF的能力.方法:从不同龋敏感儿童口腔变异链球菌中选取66株临床分离株,常规复苏、增菌并配制相同密度的菌悬液后,接种于不同pH值(以0.5为间隔,pH 5.0～7.0)的含2.5 g/L葡萄糖和0.05％ Tween 80的TYC培养基中厌氧培养18h;采用Somogyi法测定还原糖含量,计算酶活性.结果:在同一pH条件下,不同龋敏感儿童口腔变链菌GTF活性的差异具有统计学意义(P＜0.05),龋敏感性越高,GTF活性越大;同一龋敏感儿童口腔变链菌不同基因型菌株GTF活性的差异也具有统计学意义(P＜0.05),GTF活性随基因型的增加而增加;当pH5.5时,高龋、中龋儿童携带一种基因型菌株GTF活性显著下降(P＜0.05).结论:不同龋敏感儿童口腔变异链球菌不同基因型菌株在不同pH条件下GTF活性不同,携带基因型越多的菌株GTF活性越高.