The Antibacterial Activity Of Silver Nanoparticles Combined With Chlorhexidine Against Enterococcus Faecalis

Objectives: The purpose of this study was to evaluate the antibacterial efficacy of Silver Nanoparticles(AgNPs)solution against Enterococcus faecalis(E.faecalis),and to examine its antibacterial efficacy when combined with chlorhexidine(CHX)against E.faecalis biofilm.The result could lead to new options for root canal irrigants in clinical treatment.Methods: The minimum inhibitory concentration(MIC)and the minimum bactericidal concentration(MBC)of AgNPs solution and CHX solution against E.faecalis were determined by microplate reader and plate colony counting method.To evaluate the effect of the combinations of the two solutions,the fractional inhibitory concentration(FIC)was calculated.An in vitro model of E.faecalis biofilm was established to determine the killing of Enterococcus faecalis over time,where the AgNPs solution and CHX solution under MBC were used as the positive control group,and the combination of the two was used as the experimental group.The degree of dispersion of E.faecalis biofilm was detected by Confocal laser scanning microscope to determine the E.faecalis killing efficacy of the solutions in each group..Results: 1.The MIC result of AgNPs solution against E.faecalis was 12.5 μg/m L,and the MBC result was 25 μg/m L;the MIC result of CHX solution against E.faecalis was2 μg/m L,and the MBC result was 4 μg /m L.2.The FIC index was 0.75 for AgNPs solution combined with CHX solution,which shows that the two had a partial synergistic effect on the inhibition against E.faecalis.3.AgNPs solution(25 μg/m L)and CHX solution(4 μg/m L)both had a significant killing effect on the E.faecalis biofilm.The combination of the two had a stronger antibacterial effect on the biofilm than CHX solution alone,and could also kill bacteria in a shorter amount of time.4.Disruption of the E.faecalis biofilm can be observed when using AgNPs solution combined with CHX solution,as opposed to using CHX solution alone.Conclusions: The combined application of CHX solution and AgNPs solution against E.faecalis can produce a partial synergistic effect,which results in a stronger antibacterial efficacy and destruction of the biofilm structure in a shorter amount of time.