Inhibition of Bacterial Efflux Pumps by Crude Extracts and Essential Oil from <i>Myristica fragrans</i> Houtt. (Nutmeg) Seeds against Methicillin-Resistant <i>Staphylococcus aureus</i>

• Main Authors: Thidar Oo, Bhanubong Saiboonjan, Sukanya Srijampa, Arpasiri Srisrattakarn, Khaetthareeya Sutthanut, Ratree Tavichakorntrakool, Aroonwadee Chanawong, Aroonlug Lulitanond, Patcharaporn Tippayawat
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Molecules
• Subjects: nutmeg; crude extract; essential oil; methicillin-resistant <i>Staphylococcus aureus</i>; efflux pump inhibitor
• Online Access: https://www.mdpi.com/1420-3049/26/15/4662

<i>Myristica</i><i>fragrans</i> Houtt. (Nutmeg) is a widely known folk medicine across several parts of Asia, particularly used in antimicrobial treatment. Bacterial resistance involves the expression of efflux pump systems (chromosomal <i>nor</i>A and <i>mep</i>A) in methicillin-resistant <i>Staphylococcus aureus</i> (MRSA). Crude extract (CE) and essential oil (EO) obtained from nutmeg were applied as efflux pump inhibitors (EPIs), thereby enhancing the antimicrobial activity of the drugs they were used in. The major substances in CE and EO, which function as EPIs, in a descending order of % peak area include elemicin, myristicin, methoxyeugenol, myristicin, and asarone. Here, we investigated whether the low amount of CE and EO used as EPIs was sufficient to sensitize MRSA killing using the antibiotic ciprofloxacin, which acts as an efflux system. Interestingly, synergy between ciprofloxacin and CE or EO revealed the most significant viability of MRSA, depending on <i>nor</i>A and <i>mep</i>A, the latter being responsible for EPI function of EO. Therefore, CE and EO obtained from nutmeg can act as EPIs in combination with substances that act as efflux systems, thereby ensuring that the MRSA strain is susceptible to antibiotic treatment.