Inhibition of the multidrug efflux pump LmrS from Staphylococcus aureus by cumin spice Cuminum cyminum

Staphylococcus aureus is a serious causative agent of infectious disease. Multidrug-resistant strains like methicillin-resistant S. aureus compromise treatment efficacy, causing significant morbidity and mortality. Active efflux represents a major antimicrobial resistance mechanism. The proton-driven multidrug efflux pump, LmrS, actively exports structurally distinct antimicrobials. To circumvent resistance and restore clinical efficacy of antibiotics, efflux pump inhibitors are necessary, and natural edible spices like cumin are potential candidates. The mode of cumin antibacterial action and underlying mechanisms behind drug resistance inhibition, however, are unclear. We tested the hypothesis that cumin inhibits LmrS drug transport. We found that cumin inhibited bacterial growth and LmrS ethidium transport in a dosage-dependent manner. We demonstrate that cumin is antibacterial toward a multidrug-resistant host and that resistance modulation involves multidrug efflux inhibition.