Abstract:

Objective To study the detection rate of Streptococcus mutans in oral cavities of 3-5-year-old Han, Uygur and Mongolian children in Bortala Mongolian Autonomous Prefecture, and the correlation between genotype and dental caries of preschool children.Methods Ninety children were randomly selected from the sample bank of children′s oral epidemiological survey data in the Bozhou area of Xinjiang. Forty-five children were included in the high caries group (more than 5 missing teeth), and 45 children were included in the noncaries group (0 missing teeth); each group comprised 15 children of each of the Han, Uygur and Mongolian nationalities. Plaque samples were collected and cultured with light saliva-bacillin agar medium and brain-heart infusion medium. Streptococcus mutans were cultured, and clinical isolates were further isolated and identified by Gram staining, biochemical identification and polymerase chain reaction. Genotype distribution was detected by random primer polymerase chain reaction.Results The detection rate of Streptococcus mutans in the 90 included children was 75.5%. The detection rate of Streptococcus mutans in the high caries group was 86.7%, which was significantly higher than that in the caries-free group (64.4%) (P=0.014). There was no significant difference in the distribution of Streptococcus mutans among Han, Uygur and Mongolian nationalities (P=0.457). A total of 549 clinical strains of Streptococcus mutans were obtained, and 113 different genotypes were found. In the high caries group, 61.5% carried more than one genotype of Streptococcus mutans, and 37.9% of the caries-free group had more than one genotype. The genetic polymorphism of Streptococcus mutans in the high caries group was significantly higher than that in the caries-free group (P=0.035). Spearman correlation analysis showed that there was a positive correlation between oral Streptococcus mutans gene polymorphism and caries sensitivity (r=0.258, P=0.034).Conclusion The distribution of Streptococcus mutans in children′s oral cavity in the Bozhou area was different between the high caries group and the caries-free group, but there was no difference among nationalities. Streptococcus mutans in the high caries group had more genotypes than those in the caries-free group. The genetic polymorphism of Streptococcus mutans might be related to the caries-causing ability of Streptococcus mutans.

Key words: Streptococcus mutans, Children, Dental plaque, Dental caries, Genotype, Gene polymorphisms, Ethnic, Correlation

摘要：

目的 研究博尔塔拉蒙古自治州（博州）3~5 岁汉族、维吾尔族、蒙古族儿童口腔内变形链球菌的检出率,以及基因型与儿童龋病间的相关性。方法 从博州地区儿童口腔流行病学调查资料样本库中分层随机抽取 90 名儿童为研究对象,高龋组（龋失补牙数 ≥ 5）45 名,无龋组（龋失补牙数=0）45 名,每组中汉族、维吾尔族、蒙古族儿童各 15 名,收集牙菌斑样本,用轻唾-杆菌肽琼脂培养基和脑心浸液培养基培养变形链球菌,通过革兰氏染色,生化鉴定和聚合酶链反应等方法进一步分离鉴定临床分离株,并通过随机引物聚合酶链式反应检测基因型分布。结果 在 90 名受检儿童中变形链球菌的检出率为 75.5%,高龋组变形链球菌的检出率为 86.7%,高于无龋组的 64.4%（P=0.014）。汉族、维吾尔族、蒙古族间比较时,变形链球菌的检出率差异无统计学意义（P=0.457）。本实验共获得 549 株变形链球菌临床菌株,发现 113 种不同的基因型。高龋组中 61.5%的个体携带超过一种以上的变形链球菌基因型,无龋组有 37.9%的个体具有一种以上的基因型,高龋组变形链球菌基因多态性高于无龋组,差异具有统计学意义（P=0.035）。Spearman 相关分析表明,三民族儿童口腔内变形链球菌基因多态性与龋敏感度呈正相关（r=0.258,P=0.034）。结论 博州儿童口腔内变形链球菌在高龋组与无龋组间分布有差异,在民族间无差异,高龋组群体中存在的变形链球菌比无龋组拥有更多的基因型数量,其基因多态性可能与变形链球菌的致龋性能相关。

关键词: 变形链球菌, 儿童, 牙菌斑, 龋病, 基因型, 基因多态性, 民族, 相关性