Assessment of the efficacy of diosmin against methicillin-resistant Staphylococcus aureus and the underlying mechanism of action

Abstract

Objective: To investigate the antibacterial and antibiofilm activities of diosmin, a plant-derived flavonoid glycoside, against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), in response to the growing challenge of multidrug-resistant bacterial infections. Methods: The antibacterial activity of diosmin was assessed against five clinical MRSA isolates using broth microdilution method to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Antibiofilm activity was evaluated using crystal violet biofilm assay. Additionally, cell viability within biofilms was measured using a triphenyl tetrazolium chloride (TTC) assay. Results: Diosmin demonstrated a consistent MIC of 1.0 mg/mL and MBC of 2.0 mg/mL across all tested MRSA isolates, indicating primarily bacteriostatic activity at lower concentrations. Biofilm formation was significantly inhibited in a dose-dependent manner, with reductions ranging from 52% to 79% at 1.5 mg/mL. The minimum biofilm inhibitory concentration (MBIC50) values ranged from 0.0048 mg/mL to 0.0350 mg/mL. TTC assay results showed that diosmin significantly reduced viable biofilm-embedded cells at concentrations equal to or above the MIC, while sub-MIC concentrations exhibited minimal cytotoxic effects, suggesting non-lethal antibiofilm mechanisms. Conclusion: Diosmin exhibits promising antibacterial and antibiofilm activities against MRSA, with effective inhibition of biofilm formation and reduction of viable cells. These findings support its potential as a natural alternative or adjunct therapeutic agent for managing MRSA infections.