In vitro effect of glycycoumarin against Staphylococcus aureus biofilm

OBJECTIVE To evaluate the antibacterial and anti-biofilm effects of the plant-derived glycycoumarin against Staphylococcus aureus, laying a foundation for the development and application of drugs for clinical treatment of S. aureus infection.

METHODS The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of glycycoumarin against S. aureus were determined. Growth curves were plotted to observe the impact of different concentrations of glycycoumarin on bacterial growth. The effect of glycycoumarin on S. aureus biofilm formation and mature biofilms eradication were assessed through the crystal violet staining method.

RESULTS The MIC and MBC of glycycoumarin against S. aureus were both 4 μg/ml. Growth curves indicated that the inhibitory effect on bacteria was positively correlated with drug concentration. Significant antibacterial effects were observed at a glycycoumarin concentration of 0.5 μg/ml, and complete inhibition of S. aureus growth was achieved at 4 μg/ml. The drug concentration required for inhibiting biofilm formation was the same as that for inhibiting planktonic bacteria. S. aureus biofilms formed in a dose-dependent manner, and at 16 μg/ml, glycycoumarin achieved an 80.47% eradication of mature biofilms.

CONCLUSIONS Glycycoumarin exhibits good antibacterial activity against planktonic S. aureus, and for the first time its ability to inhibit biofilm formation and eradicate mature biofilms was demonstrated. This study provides new insights for the treatment of recalcitrant biofilm-associated infection.