Antimicrobial Properties Of Water-soluble Oregano Extract

BACKGROUND: Oregano is an aromatic herb that has demonstrated antimicrobial, antioxidant, and anti-inflammatory properties.1,2 However, the essential oil component of oregano contains terpene compounds that are strong sensitizers.3,4 Water-soluble oregano extract retains phenolic compounds and is obtained after distillation of the essential oil.5 A previous randomized, double-blind, controlled study using 3% water-soluble oregano extract in a petrolatum vehicle on post-surgical wounds demonstrated a decrease in S. aureus culture positivity as compared to petrolatum, with no increase in pruritis, allergic contact dermatitis, or other adverse effects.6 METHODS: Minimum inhibitory concentration (MIC) was determined for 10 microorganisms commonly implicated in skin pathology (B. subtilis, C. difficile, C. acnes, E. faecalis, E. coli, M. Furfur, MRSA, MSSA, P. aeruginosa, and S. pyogenes). This was done by growing the microorganisms on agar plates containing various dilutions of water-soluble oregano extract, and recording the lowest concentration that inhibited visible growth. RESULTS: MIC was successfully determined for 9/10 organisms: B. subtilis (0.10%), C. difficile (1.0%), C. acnes (0,50%), E. faecalis (1.0%), E. coli (10.0%), M. Furfur (0.50%), MRSA (0.75%), MSSA (0.75%), and S. pyogenes (1.0%). CONCLUSIONS: Our results support the antimicrobial properties of water-soluble oregano extract. Specifically, in vitro inhibition of MRSA, MSSA, and S. pyogenes growth may indicate a role for water-soluble oregano extract in wound care. This would decrease the risk of allergic contact dermatitis associated with common wound-healing ointments, which is attributed to ingredients such as lanolin, bacitracin, and neomycin.7 References: 1. Baricevic D, et al. The biological/pharmacological activity of the Origanum Genus. In Kintzios SE. Oregano. London and New York:Taylor & Francis; 2002: 177-214. 2. Eng W, et al. Development of an oregano-based ointment with anti-microbial activity including activity against methicillin-resistant Staphlococcus aureus. J Drugs Dermatol. 2010 Apr;9(4):377-80. 3. Hausen B, et al. Degradation products of monterpene are the sensitizing agent in tea tree oil. Am J Cont Derm. 1999; 10(2):68-77.4. de Groot A, et al. Essential Oils, Part IV: Contact Allergy. Dermatitis. 2016;27(4):170-175. 5. Havkin-Frenkel D. (Bakto Natural Preservatives, LLC., US). Recovery of residual plant components after distillation of essential oils. US Patent 0254149 A1, October 16, 2008. 6. Ragi J, et al. Oregano extract ointment for wound healing: a randomized, double-blind, petrolatum-controlled study evaluating efficacy. J Drugs Dermatol. 2011 Oct;10(10):1168-72.7. Jacobs, S, James, W. Bacitracin after clean surgical procedures may be risky. J Am Acad Dermatol. 2004; 51(6):1036.