Examination of caries-risk person by selective media for S.mutans and S.sobrinus

本研究旨在改进变形链球菌选择性培养基。在MS-MUT培养基中加入10 mg/L缬氨霉素，制成一种新的选择性培养基MS-MUTV，其平均回收率为72.1%，远缘链球菌、咽峡炎链球菌在MS-MUTV上生长受到抑制，而在MS-MUT上生长正常。对139份人唾液样本进行了检查，并对变形链球菌和非变形链球菌菌落进行了计数。MS-MUTV上的变形链球菌回收率与MS-MUT上的相似。82%和7.9%的唾液样本分别获得了在MS-MUTV上没有细菌生长的变形链球菌纯培养物。其余10.1%被低水平CFU的非变形链球菌污染。MS-MUTV可用于临床标本中变形链球菌的分离，本研究的目的是探讨变形链球菌的性质差异与龋病患病率的关系。在口腔学校选择10名患龋者和10名无龋者。收集他们的唾液，并从每个受试者中分离出一种变形链球菌菌株，然后进行鉴定。比较两组菌株的不溶性葡聚糖合成、蔗糖依赖性定植、产酸能力、耐酸性和gtfB表达。两组变形链球菌的牢固定殖能力、最终pH产酸能力、耐酸性和gtfB表达量差异均无统计学意义。

The aim of this study was to improve the selective medium of Streptococcus mutans. A new selective medium, designated MS-MUTV, was prepared by adding 10mg/l valinomycin to the MS-MUT medium previously described.The average recovery of S.mutans was 72.1% and growth of S.sobrinus, S.anginousus group was inhibited on MS-MUTV, but allowed on MS-MUT. One hundred and thirty-nine human saliva samples were examined and counted for S.mutans and non-S.mutans colonies. The recovery of S.mutans on MS-MUTV was similar to that on MS-MUT. Eighty-two and 7.9 percent of the saliva samples obtained S.mutans pure cultures with no bacterial growth on MS-MUTV, respectively. The remaining 10.1% were contaminated with non-S.mutans with low level CFU. MS-MUTV is useful for isolation of S.mutans alone from clinical samples in routine examinations.The aim of this study was to clarify the correlation between caries prevalence and qualitative difference of S.mutans. Ten caries-susceptible and ten caries-free persons were selected in dental school. Their saliva was collected, and one IS.mutans strain was isolated from each subject and then identified. The insoluble glucan synthesis, sucrose-dependent firm colonization, the acid productivity, the acid tolerance and the expression of gtfB in S.mutans isolates from both groups were compared. As to the firm colonization ability, the final pH test of acid productivity, the acid tolerance and the expression of gtfB, there were no significant differences between S.mutans isolates from both groups.