Australian propolis ethanol extract exerts antibacterial activity against methicillin-resistant Staphylococcus aureus by mechanisms of disrupting cell structure, reversing resistance, and resisting biofilm

• Published in: Brazilian journal of microbiology Vol. 52; no. 4; pp. 1651 - 1664
• Main Authors: Wang, Fei, Liu, Hui, Li, Junya, Zhang, Wenwen, Jiang, Bin, Xuan, Hongzhuan
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2021; Springer Nature B.V
• Subjects: Anti-Bacterial Agents - pharmacology; Antibacterial activity; Assaying; Australia; Bacterial and Fungal Pathogenesis - Research Paper; Biofilms; Biofilms - drug effects; Biomedical and Life Sciences; Cell walls; Cellular structure; Cytology; Cytoplasmic membranes; Disruption; Drug resistance; Ethanol; Ethanol - chemistry; Food Microbiology; High-performance liquid chromatography; Iodides; Life Sciences; Liquid chromatography; Medical Microbiology; Membranes; Methicillin; Methicillin-Resistant Staphylococcus aureus - drug effects; Microbial Ecology; Microbial Genetics and Genomics; Microbial Sensitivity Tests; Microbiology; Minimum inhibitory concentration; Mycology; Nucleic acids; Plant Extracts - pharmacology; Propidium iodide; Propolis; Propolis - chemistry; Propolis - pharmacology; Scanning electron microscopy; Staphylococcus aureus; Staphylococcus infections; β Lactamase; Australia; Cell structure; Biofilm; Australian propolis; Drug resistance; Methicillin-resistant; Methicillin-resistant Staphylococcus aureus
• ISSN: 1517-8382; 1678-4405
• DOI: 10.1007/s42770-021-00547-7

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.