Inhibitory Effect Of Grape Seed Proanthocyanidin Extract On Growth, Acid Production Of Streptococcus Mutans And Caries Incidence Of Rats

OBJECTIVE:To study the effect of grape seed proanthocyanidin extract(GSPE)on the growth,the acid production of Streptococcus mutans(S,mutans)in vitro,and caries incidence of rats infected with S.mutans.METHODS:Experiment One:Two strains of mutans streptococci,S.mutans Ingbritt and S. sobrinus 6715,were recovered in tryptic soy broth(TSB)medium containing 1% glucose at anaerobic atmosphere(CO₂80%,N₂10%,H₂10%)for this study.The minimum inhibitory concentration(MIC)and the minimum bactericidal concentration(MBC) were determined using a standard susceptibility agar dilution technique.GSPE containing over 95%proanthocyanidin and tea polyphenols(TP)containing 90% catechins for S.mutans were used in the study.After S.mutans were cultured in TSB or in TSB with MIC of GSPE at 37℃at anaerobic atmosphere for 24 h,the pH values of the bacterial suspension were measured.This experiment repeated four times.After S.mutans were cultured in TSB or in TSB containing the half concentration of MIC of GSPE at 37℃at anaerobic atmosphere for 24 h,they were centrifugated and washed three times by physiological saline.After S.mutans were fixed,dyed and embedded,the bacterial morphology were observed by transmission electronic microscope(TEM).Experiment Two:Twenty-four 21-day-old Sprague-Dawley(SD)rats were devided randomly into three groups(8 rats per group),fed with diet containing ampicillin(0.5 mg/g)and chloromycin(0.5 mg/g)for 3 consecutive days(from 21 to 23 days of age). All rats were inoculated with S.sobrinus 6715 once a day for 5 consecutive days (from 24 to 28 days of age),and fed with caries-inducing diet 2000.The mouths of rats were rinsed with one of three solutions(Group A:GSPE at the MIC concentration;Group B:TP at the MIC concentration;Group C:sterilized distilled water)once a day till the end of the experiment.All rats were sacrificed for scoring caries of 12 molar teeth of each rat by Keyes' method at age of 89 days.The data were analyzed with t tests and nonparametric tests in SPSS 13.0 version.RESULTS:Experiment One::â‘ The MIC and MBC of GSPE against Streptococcus mutans were 4 mg/ml and 8 mg/ml,while the MIC and MBC of TP were 2 mg/ml and 4 mg/ml.â‘¡GSPE revealed a doze-dependent inhibition on the acid production by S. mutans Ingbritt and S.sobrinus 6715.â‘¢TEM findings revealed that GSPE caused the vacuolar degeneration and cell membranes destruction of Streptococcus mutans.Experiment Two:Both GSPE and TP significantly reduced the incidence of enamel caries(E)and slight dentinal caries(Ds)of molar teeth of rats(P＜0.05),compared with the control group.However,extensive dentinal caries(Dx)occurred only in the control group.And there is no significant difference between GSPE group and TP group.CONCLUSION:GSPE could inhibit the growth and acid production of S.mutans, cause the vacuolar degeneration and cell membranes destruction of Streptococcus mutans,and reduce caries incidence of SD rats infected with S.mutans.This study suggests that GSPE might be used as a mouth rinse for caries prevention.