Abstract
Background: Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant global health threat due to its multidrug resistance. Epigallocatechin gallate (EGCG), a major catechin in green tea, exhibits antibacterial properties and may enhance the efficacy of conventional antibiotics. This study evaluated the synergistic effects of EGCG with oxacillin and vancomycin against MRSA clinical isolates.Methods: Minimum inhibitory concentrations (MICs) of EGCG, oxacillin, and vancomycin were determined for 30 MRSA isolates using the broth microdilution method. Synergy was assessed by checkerboard assay and time-kill kinetics. Biofilm inhibition was quantified by crystal violet staining. Cytotoxicity was evaluated on human keratinocytes (HaCaT).Results: EGCG exhibited intrinsic anti-MRSA activity (MIC range 32–128 µg/mL). In combination, EGCG reduced the MIC of oxacillin by 4- to 16-fold (fractional inhibitory concentration index ≤ 0.5) in 70% of isolates. Time-kill assays showed bactericidal synergy at 4× MIC combinations. Biofilm formation was inhibited by up to 65% at sub-MIC concentrations. Cytotoxicity was negligible at synergistic concentrations (IC50 > 200 µg/mL).Conclusions: EGCG demonstrates potent synergistic activity with β-lactam antibiotics against MRSA and inhibits biofilm formation, suggesting its potential as an adjunctive agent. Further in vivo studies are warranted.