Synergistic effects of silver ions and metformin against enterococcus faecalis under high-glucose conditions in vitro
Xuying Wu, Wei Fan, Bing Fan
Abstract
Abstract Background This study aimed to evaluate the synergistic antibacterial activities of silver ions (Ag + ) and metformin hydrochloride (Met) against Enterococcus faecalis ( E. faecalis ) under normal or high-glucose conditions. Results The minimum inhibitory concentration, minimum bactericidal concentration, growth curves, and colony-forming units were used to evaluate the antibacterial effects of Ag + and Met on planktonic E. faecalis in Brain Heart Infusion broth with or without additional glucose. The influences of Ag + and Met on four weeks E. faecalis biofilm on human dentin slices was also tested. Cytotoxicity was tested on MC3T3-E1 osteoblastic cells using CCK-8 assays. The results indicated that E. faecalis showed higher resistance to drug treatment under high-glucose conditions. Ag + (40 μg/mL) plus Met (3.2% or 6.4%) showed enhanced antibacterial activities against both planktonic E. faecalis and biofilm on dentin slices, with low cytotoxicity. Conclusions Met enhanced the bactericidal effects of Ag + against both planktonic and biofilm E. faecalis under normal or high-glucose conditions with low cytotoxicity. Further molecular studies are needed to be conducted to understand the mechanisms underlying the synergistic activity between Met and Ag + .