Study On The Inhibitory Effect Of Green Tea Extract EGCG On Streptococcus Mutans Of Cariogenic Bacteria

Objective Dental caries is a chronic and progressive disease of dental hard tissues mainly of bacteria.Streptococcus mutans is one of the recognized cariogenic bacteria.As a natural antibacterial drug,epigallocatechin gallate(EGCG)has many functions in inhibiting bacteria.The minimum inhibitory concentrations of EGCG against Streptococcus mutans were determined by antibacterial test and the effects of different concentrations of EGCG on the optical density,hydrogen ion concentration,adhesion capacity and GTF activity of Streptococcus mutans were tested,and the antibacterial activities of EGCG were studied to provide more experimental evidences for the prevention and treatment of dental caries.EGCG has been effectively used as a natural,safe and non-drug resistant substance in order to become a good drug for the prevention and treatment of dental caries.Methods The minimum inhibitory concentrations(MIC)of EGCG against Streptococcus mutans were determined by liquid double dilution method and agar dilution method.EGCG with 2 MIC,1 MIC,1/2 MIC,1/4 MIC and 1/8 MIC were selected and anaerobically incubated with Streptococcus mutans at 0 h,4 h,8 h,12 h,24 h,and 48 h.The concentration was measured at each concentration.Bacterial optical densities were taken and growth curves were drawn.EGCG with 2 MIC,1 MIC,1/2 MIC,1/4 MIC and 1/8 MIC were also incubated anaerobically with Streptococcus mutans at 0 h,4 h,8 h,12 h,24 h,and 48 h.PHs were taken and acid production curves were drawn.After anaerobically incubated with EGCG of 1 MIC,1/2 MIC,1/4 MIC and 1/8 MIC for 24 hours with Streptococcus mutans,the effect of different concentrations of EGCG on bacterial adhesion was determined.1 MIC,1/2 MIC,1/4 MIC and 1/8 MIC of EGCG were also incubated with Streptococcus mutans for 24 h.The total protein content was determined by Coomassie brilliant blue method.The amount of reducing sugar was determined by Neson-Somogyi method.The effects of different concentrations of EGCG on the activity of GTF were calculated.The bacterial liquid group as a control group was compared with the experimental groups.All the experimental data were used SPSS 16.0 statistical software for statistical analysis.Results Compared with the bacterial liquid group and the blank control group,the MIC of EGCG was 6.25 mg/L which was detected by two methods.With the increase of EGCG concentration,the optical densities of bacteria showed a decreasing trend.The growth curves of 2 MIC and 1 MIC solution groups were gentle and low,and the curve of 2 MIC group was almost linear.The 1/4 MIC group had a weaker inhibitory effect at 12 h.In the acid production experiments,the EGCG in 2 MIC,I MIC,1/2 MIC,and 1/4 MIC concentration groups at various time periods can inhibit Streptococcus mutans acidogenic capacity with significant difference.With the increase of EGCG concentrations,the rates of bacterial adhesion decreased gradually,and there were differences between the three liquid medicine groups of I MIC,1/2 MIC and I/4MIC and the bacterial liquid group.With the increase of drug concentrations,the activity of GTF tended to decrease.Conclusions EGCG can effectively inhibit the growth and reproduction of Streptococcus mutans and inhibit its acid production and important enzymes activities.As a natural,safe and drug-free drug,EGCG may become a new direction for the prevention and treatment of dental caries.