Abstract:

 Objective  This study aimed to investigate the effect of a lactoperoxidase-peroxidase-thiocyanate (LPO-H2O2-SCN-) systemwith different concentrationsof iodine (I-) on Streptococcus mutans (S.mutans),particularlyon various parameters, includinggrowth, adhesion, glucosyltransferase (GTF)enzyme activity,and insoluble exopolysaccharidesynthesis. 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-H2O2-SCN-system with I-on the cariogenicinity of S.mutans was strengthened as I-concentration was increased. At I-concentration≥100 μmol•L-1, the antibacterial effects were significantly increased compared with those of the control group (P<0.05). At I-concentration≥ 1 000 μmol•L-1, the antibacterial effects were significantly improved compared with those of the group with SCN-only (P< 0.05). At I-concentration≥100 μmol•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-H2O2-SCN-system with different concentrations of I-showed statistically significant inhibitory effectson growth, adhesion, insoluble exopolysac-charide synthesis,andGTF enzyme activity.

Key words: Streptococcus mutans, lactoperoxidase, iodine, thiocyanate, glucosyltransferase, insoluble exopolysaccharides