The antibacterial activity and mechanisms of Australian propolis ethanol extract (APEE) against methicillin-resistant Staphylococcus aureus (MRSA) were investigated herein. The diameter of inhibition zones (DIZ) of APEE was 19.7 mm, while the minimum inhibition concentration (MIC) and minimum bactericide concentration (MBC) of APEE were both 0.9 mg/mL against the tested strain of MRSA. Nucleic acid leakage and propidium iodide (PI) staining assays showed that APEE can stimulate the release of intracellular nucleic acids by disrupting the integrity of the cell wall and cytoplasmic membrane. Scanning electron microscopy (SEM) further confirmed that APEE could depress cellular activities via damaging the cell structure, including the cell wall and membrane. Western blot analysis and β-lactamase activity assay showed that APEE could inhibit the expression of PBP2a and reduce the activity of β-lactamase, suggesting that APEE is able to reverse the drug resistance of MRSA. XTT and crystal violet (CV) assays indicated that APEE had the capacity to prevent the formation of biofilms through decreasing cellular activities and biomass. Bacterial adhesion assay revealed that APEE could reduce the adhesive capacity of the strain, belonging to its antibiofilm mechanisms. Furthermore, nine main compounds of APEE were identified and quantified by HPLC–DAD/Q-TOF–MS. The results above all verified that the antibacterial activity of APEE against MRSA was mainly due to disrupting cell structure, reversing resistance, and resisting biofilm formation, which indicates that APEE is expected to be an efficient functional ingredient with great potential application in the field of medicine and food.

澳大利亚蜂胶乙醇提取物（APEE）对耐甲氧西林金黄色葡萄球菌的抗菌活性及作用机制(MRSA) 在此进行了研究。APEE的抑菌圈直径（DIZ）为19.7 mm，APEE对MRSA的最低抑菌浓度（MIC）和最低杀菌浓度（MBC）均为0.9 mg/mL。核酸渗漏和碘化丙啶 (PI) 染色测定表明，APEE 可以通过破坏细胞壁和细胞质膜的完整性来刺激细胞内核酸的释放。扫描电子显微镜 (SEM) 进一步证实 APEE 可以通过破坏细胞结构（包括细胞壁和细胞膜）来抑制细胞活动。Western blot分析和β-内酰胺酶活性测定表明，APEE可以抑制PBP2a的表达，降低β-内酰胺酶的活性，提示APEE能够逆转MRSA的耐药性。XTT 和结晶紫 (CV) 测定表明 APEE 具有通过降低细胞活性和生物量来防止生物膜形成的能力。细菌粘附试验表明，APEE可以降低菌株的粘附能力，属于其抗生物膜机制。此外，通过 HPLC-DAD/Q-TOF-MS 鉴定和量化了 APEE 的九种主要化合物。以上结果验证了APEE对MRSA的抗菌活性主要是由于破坏细胞结构、逆转耐药性和抵抗生物膜形成，这表明APEE有望成为一种高效的功能成分，在医药领域具有巨大的应用潜力。和食物。