Antimicrobial Effects and Resistant Regulation of Magnolol and Honokiol on Methicillin-ResistantStaphylococcus aureus

摘要

The antimicrobial killing activity toward methicillin-resistantStaphylococcus aureus(MRSA) has been a serious emerging global issue. In a continuing search for compounds with antibacterial activity against several microorganisms includingS. aureusand MRSA, ann-hexane extract ofMagnolia officinaliswas found to contain magnolol. This compound exhibited potent activity againstS. aureus, standard methicillin-susceptibleS. aureus(MSSA), and MRSA as well as clinical MRSA isolates. When combined with oxacillin, the antibacterial activities of magnolol and honokiol against the MRSA strain were increased compared to single treatment without antibiotics at 10 µg/mL and 25 µg/mL, respectively. These activities of magnolol and honokiol were dose dependent. Also, magnolol showed synergistic effects with oxacillin against 13 clinical isolates of MRSA. It was determined that magnolol and honokiol had a synergistic effect with oxacillin against MRSA strain. Furthermore, the magnolol inhibited the expression of the resistant genes,mecA, mecI, femA, andfemB, in mRNA. We concluded that the antibacterial activity of magnolol against MRSA strain is more related to themecI’s pathway and components of the cell wall thanmecR1. Therefore, the results obtained in this study suggest that the combination of magnolol and antibiotics could lead to the development of new combination antibiotics against MRSA infection.