In vitro synergistic evaluation of Nisin and NaF on Streptococcus mutans
Objective:To study the effects of the combined application of NaF and Nisin on Streptococcus mutans(S.mutans).Meth-ods:The minimum inhibitory concentration(MIC)of Nisin and NaF against S.mutans was determined by microdilution method respec-tively.The fractional inhibitory concentration(FIC)was calculated by checkerboard method.The inhibition effect of the combination of NaF and Nisin at(NF)the same MIC concentration on acid production and acid resistance of S.mutans was detected.Crystal violet staining was used to detect the effects of NF in the inhibition of the biofilm formation,and the damage and dispersion of the established biofilms.The changes of the biofilms were observed by CLSM.Results:The MIC of NaF and Nisin was 0.6 mg/mL and 20 mg/mL re-spectively.The FIC was 0.75.The 1/8×MIC NF showed significantly higher inhibition on acid production and biofilm formation than 1/4×MIC NaF or Nisin(P＜0.05),but it has no obvious dispersion effect on established biofilms.The 1/2×MIC NF showed stronger in-hibition effect on the acid resistance of S.mutans in the membrane than 1×MIC NaF or Nisin(P＜0.05).At the concentration of 2x MIC,any component didn't cause obvious damage on the established biofilm structure.Conclusion:Nisin and NaF have synergistic in-hibitory effects on the proliferation,acid production,acid resistance and biofilm formation of S.mutans.
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