Anti-Biofilm Activity of Marrubium vulgare L. (Lamiaceae) Extract on MRSA

Abstract

Many plants possess potent antimicrobial agents and provide effective remedies for skin conditions. Infusions of the aerial parts of Marrubium vulgare (white horehound) are used in the south Italian pharmacopoeia as a rinse for skin rashes and wounds [1]. Staphylococcus aureus, a common cause of skin infections, has generated increasing concern among health care professionals due to the prevalence of drug resistant strains. Identification of novel antibiotics and anti-biofilm agents for methicillin-resistant S. aureus (MRSA) is important to healthcare on a global scale. The aim of this study was to evaluate extracts from Marrubium vulgare for in vitro inhibition of planktonic growth, biofilm formation and adherence in MRSA. A broth microtiter dilution method was employed to determine the MIC after 18 hours growth using an optical density (OD600nm) reading using a MRSA isolate (ATCC 33593). The impact of extracts on biofilm formation and adherence was tested by growing biofilms for 40 hours, then fixing and staining with crystal violet. After washing, 10% Tween 80 was added and OD570 nm readingswere taken. A crude ethanolic extract of the rootswas the most effective at inhibiting both biofilm formation (IC50 = 32 μg/ml) and adherence (IC50 = 8 μg/ml). A significant dose-dependent response for the inhibition of both biofilm formation and adherencewas evident. Acknowledgements: This work was funded by NIH/NCCAM F32AT005040 (PI: C. L. Quave).