重度龋儿童远缘链球菌基因多态性研究

Genotypic diversity of Streptococcus sobrinus in 3 to 4-year-old children suffering with severe early childhood caries

目的采用随机引物聚合酶链反应（arbitrarily primed-polymerase chain reaction，AP-PCR）法初步探讨远缘链球菌在重度低龄儿童龋（severe early childhood caries，S-ECC）儿童与无龋儿童口腔中基因型分布的情况，分析其与婴幼儿龋发生之间的关系。方法选取北京市海淀区和西城区14所幼儿园178名42-54个月龄儿童，S-ECC（患龋牙数≥5）组87例，无龋组91人。嚼蜡法采集刺激性唾液进行分离培养，典型菌落行革兰染色、生化鉴定并保种，提取基因组DNA，PCR鉴定变形链球菌和远缘链球菌，AP-PCR法对远缘链球菌临床分离株行基因型分析。结果S-ECC组远缘链球菌检出率18％（16／87），显著高于无龋组的3％（3／91），差异有统计学意义（P〈0.01）。53株远缘链球菌临床分离株共检出22种基因型，S-ECC组个体基因型为1-3种，无龋组均为1种；此外，S-ECC组3名个体间存在相同基因型的菌株。S-ECC组基因型数与龋失补牙数间存在相关性（r=0.50，P〈0.05）。结论S-ECC儿童远缘链球菌检出率明显高于无龋儿童，且菌株间存在基因多态性，个体携带基因型的种类数与其致龋性间存在相关性；远缘链球菌无关个体间存在相同基因型的菌株。

Objective To evaluate the genotypic diversity of Streptococcus sobrinus （Ss）between children suffering with severe early childhood caries （S-ECC） and caries-free children by arbitrarily primed- polymerase chain reaction（AP-PCR）. Methods A total of 178 children aged from 42 to 54 months were recruited from 14 urban kindergartens. The S-ECC group contained 87 children with more than 5 decayed teeth, and the control group was composed of 91 caries-free children. Stimulated whole saliva was collected by chewing paraffin. All mutans streptococcus isolates were subcuhured, biochemically eharacterised and identified by PCR as Streptococcus mutans （Sm） and Ss. Then the Ss isolates were genotyped by AP-PCR. Results The frequency of Ss detection was 18% in S-ECC children, which was significantly higher than 3% in caries-free children （P 〈0. 01）. Twenty-two distinct genotypes of Ss were identified from 53 clinical isolates. In S-ECC group, one to three genotypes of Ss were detected in each saliva sample. Only one genotype of Ss was detected in all the caries-free children. One genotype of Ss were shared by three S-ECC children. The genotypes of isolates in S-ECC group were relate to decayed-missing-filled teeth （r = 0. 50, P 〈 0. 05 ）. Conclusions The rate of Ss detection was significantly higher in S-ECC children than in caries-free children. Isolates of Ss displayed genetic polymorphism. The multi-genotypes of Ss was related to differences in caries susceptibility. Strains of Ss with same genotype were present in unrelated subjects.