Carvacrol potentiates gentamicin against Staphylococcus aureus via disrupting bacterial respiratory bioenergetics

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) calls for novel antibiotic adjuvants. Carvacrol (Car), a natural monoterpene phenol derived from the essential oils of aromatic plants, exhibits membrane-active properties and has potential as an antibacterial adjuvant. Here, we found that Car markedly enhanced the bactericidal activities of Gentamicin (Gen) against MRSA. Mechanistically, Car dissipated membrane potential, inhibited respiratory chain dehydrogenase activity, and depleted intracellular ATP. Moreover, Car promoted membrane lipid peroxidation, ultimately leading to structural and functional membrane damage and bacterial death. Notably, pharmacological perturbation of respiratory and metabolic pathways further supported that this synergistic effect depends on bacterial respiratory bioenergetics. In addition, the combination showed favorable in vivo antibacterial efficacy in both Galleria mellonella and murine infection models, without apparent toxicity under the tested conditions. Collectively, these findings indicate that Car may serve as a natural antibacterial adjuvant for combination therapy against drug-resistant infections.