Propolis Exerts Antibiofilm Activity Against Methicillin-Resistant Staphylococcus aureus by Modulating Gene Expression to Suppress Adhesion

Within the global epidemiological landscape, methicillin-resistant Staphylococcus aureus (MRSA) stands out as a major contributor to infectious disease burden. The persistent public health crisis it presents arises from a dual challenge: intrinsic multidrug resistance coupled with a high rate of healthcare-associated infections. Recent studies have shown that propolis has unique advantages in bacterial infection prevention and treatment. The present study revealed that propolis ethanolic extract (PEE) exhibited notable antibacterial activity against both MRSA ATCC 43300 and MRSA CI2, with a minimum inhibitory concentration (MIC) of 128 μg/mL for each strain. Crystal violet (CV) staining and XTT sodium reduction assays were employed to evaluate the anti-biofilm efficacy of PEE. CV staining revealed that PEE significantly inhibited biofilm formation and reduced the biomass of pre-formed biofilm. Additionally, the XTT sodium reduction assay demonstrated a substantial reduction in the metabolic activity of the biofilm-embedded. Scanning electron microscopy and bacterial adhesion experiments revealed that PEE significantly reduced bacterial adhesion and aggregation. Furthermore, experiments on the synthesis of extracellular polysaccharides and proteins showed that PEE inhibits the production of water-soluble and alkali-soluble polysaccharides and extracellular proteins. Real-time quantitative Polymerase Chain Reaction (RT-qPCR) analysis revealed that PEE inhibited the expression of icaADBC, fnbAB, clfAB, and sarA. These results revealed that PEE inhibits biofilm formation and development by inhibiting the expression of sarA, icaADBC, fnbAB, and clfAB, thereby reducing the synthesis of extracellular polysaccharides and proteins to attenuate the adhesion capacity of MRSA. In summary, this study provides experimental evidence for the development of PEE as a potential antimicrobial agent for the prevention and treatment of MRSA-associated infections. Future work will focus on identifying its key active monomers and investigating its therapeutic effects and mechanisms of action in animal models.