含碘的乳过氧化物酶-过氧化氢-硫氰化物系统对变异链球菌致龋性的影响

In vitro study of the effect of a lactoperoxidase-peroxidase-thiocyanate system with iodine on the cariogenicinity of Streptococcus mutans

目的研究含不同浓度碘(I-)的乳过氧化物酶-过氧化氢-硫氰化物系统(LPO-H2O2-SCN-)对变异链球菌生长、黏附、产水不溶性细胞外多糖以及葡萄糖基转移酶(GTF)活性的影响。方法选用S.mutans ATCC 25175为实验菌株。采用菌落形成单位(CFU)计数法进行生长实验;用分光光度计法测定细菌的黏附抑制率;用蒽酮法测定水不溶性细胞外多糖的质量浓度;用蒽酮法测定还原糖量,计算GTF活性。结果随着I-浓度的增高,含I-的LPO-H2O2-SCN-抗菌系统对S.mutans致龋力的抑制作用增强。当I-≥100μmol·L-1时,对S.mutans的生长抑制明显高于对照组(P<0.05);且当I-≥1 000μmol·L-1时,对S.mutans的生长抑制显著高于以硫氰酸盐(SCN-)为单底物的实验组(P<0.05);当I-≥100μmol·L-1时,对S.mutans的黏附抑制率达到50%以上,水不溶性细胞外多糖生成量明显减少(P<0.05),GTF活性也明显降低(P<0.05)。结论通过增加I-的浓度,可以抵消生理浓度的SCN-的抑制作用,使含I-的LPO-H2O2-SCN-系统能显著抑制变异链球菌的生长、黏附、水不溶性细胞外多糖生成和GTF活性。

Objective This study aimed to investigate the effect of a lactoperoxidase-peroxidase-thiocyanate （LPO-H202- SCN-） system with different concentrations of iodine （I） on Streptococcus mutans （S. mutans）, particularly on various parameters, including growth, adhesion, glucosyltransferase （GTF） enzyme activity, and insoluble exopolysaccharide synthesis. Methods S. mutans ATCC 25175 was used as experimental species. Clonal formation unit （CFU） were counted to investigate the inhibi- tory effect on bacterial growth. The inhibition rate of bacterial adherence was calculated to analyze the effect on adhesion. Anthrone method was used to determine the content of insoluble exopolysaccharides and the amount of reducing saccharides. GTF activity and enzyme activity were then determined. Results The inhibitory ability of the LPO-H202-SCN- system with I on the cariogenicinity of S. mutans was strengthened as I concentration was increased. At I- concentrationI-≥100μmol·L^-1, the antibacterial effects were significantly increased compared with those of the control group （P〈0.05）. At I- concentrationI-≥100μmol·L^-1, the antibacterial effects were significantly improved compared with those of the group with SCN-only （P〈 0.05）. At I concentrationI-≥100μmol·L^-1, the inhibition rate of bacterial adherence was〉50%; insoluble exopolysaccharide synthesis and GTF enzyme activity were reduced （P〈0.05）. Conclusion The antibacterial effects of the LPO-H2O2-I- system were enhanced by adding I- to overcome the antagonistic effect of physiological SCN- concentration. LPO-HzO2-SCN- system with different concentrations of I- showed statistically significant inhibitory effects on growth, adhesion, insoluble exopolysac- charide synthesis, and GTF enzyme activity.