高龋学龄前儿童变形链球菌的水平传播方式

Horizontal transmission of Streptococcus mutans in caries-active preschool children

目的：研究高龋学龄前儿童变形链球菌的水平传播方式，为儿童龋病早期预防提供依据。方法收集20名4~5岁高龋学龄前儿童口腔中牙菌斑标本进行厌氧培养，通过细菌形态学观察、生物化学鉴定、聚合酶链反应（PCR）扩增变形链球菌基因的特异性片段葡糖基转移酶B（gtfB）以及随机引物聚合酶链反应（AP-PCR）等方法对获得的变形链球菌临床分离株进行鉴定。结果从20例高龋学龄前儿童口腔中分离获得200株变形链球菌临床分离株，经生物化学鉴定排除其中19株，获得181株变形链球菌临床分离株，变形链球菌的特异性基因gtfB的PCR扩增181株变形链球菌临床分离株均鉴定为变形链球菌，AP-PCR发现37种不同基因型，其中6名儿童携带1种基因型，11名儿童携带2种基因型，2名儿童携带3种基因型，1名儿童携带4种基因型，有2名不同班级儿童携带一种相同基因型。结论获得37株不同基因型变形链球菌临床分离株，高龋学龄前儿童间未发现变形链球菌水平传播。

Objective To analyze horizontal transmission patterns of Streptococcus mutans among caries-active preschool children for early interventions of dental caries. Methods Plaque samples obtained from 20 caries-active preschool children between 4 and 5 years of age were cultured under anaerobic conditions for isolating S. mutans, which were identified by morphological and biochemical analyses and PCR using primers homologous to the surface protein glucosyltransferase B （gtfB）. The genotypes of the isolated S. mutans strains were determined by arbitrarily primed PCR （AP-PCR）. Results Of the 200 S. mutans isolates obtained, 19 were excluded by biochemical analysis, and the remaining 181 isolates were identified as S. mutans by PCR with primers of gtfB, showing 37 different genotypes as identified by AP-PCR. Six children were found to carry S. mutans of a single genotype, 11 carried 2 genotypes, 2 had 3 genotypes, and 1 had 4 genotypes;2 children from different classes were found to carry S. mutans of the same single genotype. Conclusion We identified 37 genotypes of S. mutans in these caries-active preschool children, among whom horizontal transmissions of the strains were not found.