Study On The Effect Of New Antimicrobial Substance DAPC On Streptococcus Mutans And Porphyromonas Gingivalis

Objectives:1.evaluate the antibacterial activity of DAPC on Streptococcus mutans and Porphyromonas gingivalis by MIC and MBC test;2.explore the effect of DAPC on virulence gene expression of Streptococcus mutants and Porphyromonas gingivalis;3.Comparing the property of DAPC to prevent Streptococcus mutans and Porphyromonas gingivalis' adhesion on enamel surface and reflect the adhesion property of DAPC to enamel.Methods:1.determine the MIC and MBC of DAPC and chlorhexidine gluconate by liquid dilution method;2.detect the expression quantity of gtfB,gtfC gene of Streptococcus mutans and rgpA gene of phyromonas gingivalis by Real-time qPCR after affected by MIC and MBC concentration acquired in last step,TPY Broth Medium as the negative control of Streptococcus mutans and brain heart infusion broth as the negative control of Porphyromonas gingivalis,chlorhexidine gluconate as the positive control for both.3.Measure the quantity of biofilm of Streptococcus mutans and Porphyromonas gingivalis on enamel surface soaked in different concentration of DAPC by crystal violet staining,chlorhexidine gluconate as the positive control,and PBS as the negative control.Results:1.The MIC of DAPC on Streptococcus mutans was 31.25?g/ml,and MBC was 62.5?g/ml.The MIC of chlorhexidine gluconate on Streptococcus mutans was 15.625?g/ml,while the MBC was 31.25?g/ml.The MIC of DAPC on Porphyromonas gingivalis was 3.90625?g/ml,and MBC was 3.90625?g/ml too.The MIC of chlorhexidine gluconate on Porphyromonas gingivalis was 1.95312?g/ml,while the MBC was 3.90625?g/ml.2.After exposure to DAPC with MIC and MBC concentration,the expression of gtfB,gtfC gene of Streptococcus mutans were significantly lower than TPY group,a statistical difference is found(P<0.01),but there was no statistical difference among DAPC's MIC?MBC group and chlorhexidine gluconate's MBC group(P>0.05).After exposure to 1/2MBC and MBC concentration of DAPC,the expression of rgpA gene of Porphyromonas gingivalis was significantly lower than BHI group(P<0.01),and there was no statistical difference among DAPC's 1/2MBC and MBC group and chlorhexidine gluconate's MIC and MBC group(P>0.05).3.DAPC and chlorhexidine gluconate at MIC showed no inhibitory effect on adhesion to enamel for both bacteria(P>0.05).(1)the formation of biofilm in DAPC group was significantly lower than TPY group when DAPC was 250?g/ml in Streptococcus mutans(P<0.01),but higher than chlorhexidine gluconate when the concentration was 125?g/ml within 24 hours(P<0.01),however,there was no statistical difference between them after 48 hours(P>0.05).The biofilm formation of Streptococcus mutans in DAPC group was significantly lower than that in negative control group when the concentration was 2400?g/ml(P<0.01),higher than 1200?g/ml of chlorhexidine gluconate within 24 hours(P<0.01),but after 24 hours there was no statistical difference between DAPC and chlorhexidine gluconate(P>0.05).(2)For Porphyromonas gingivalis,there was no difference in the biofilm quantity between the experimental group and BHI group within 24 hours exposed to all chosen concentration of DAPC in this study(P>0.05),but the biofilm quantity of Porphyromonas gingivalis was significantly reduced(P<0.01)after 48 hours when concentration of DAPC was 62.5?g/ml and there was no difference between 62.5?g/ml DAPC and 31.25?g/ml chlorhexidine gluconate(P>0.05).Moreover,after 72 hours,the biofilm quantity of 62.5?g/ml DAPC group was significantly lower than 31.25?g/ml' chlorhexidine gluconate(P<0.05).The biofilm quantity of Porphyromonas gingivalis was significantly reduced after 48 hours When concentration of DAPC was 2400?g/ml,(P<0.01).After the 48 hours and 72 hours,there was no statistical difference between 2400?g/ml DAPC group and1200?g/ml chlorhexidine gluconate group about biofilm quantity(P>0.05).Conclrusions:1.DAPC showed good antibacterial activity for Streptococcus mutans and Porphyromonas gingivalis.2.The MIC and MBC of DAPC can significantly inhibit the expression of Streptococcus mutans'gtfB,gtfC gene and Porphyromonas gingivalis'rgpAgene.3.Concentration of DAPC above 250?g/ml can effectively inhibit the adhesion of Streptococcus mutans.Concentration of DAPC above 62.5?g/ml can inhibit the adhesion of Porphyromonas gingivalis effectively.