In vitro anti-MRSA activity of carvone with gentamicin

Carvone is one of the naturally occurring monoterpenes, the largest class of secondary metabolites in plants, and exists in two enantiomers, R‑carvone (R‑car) and S‑car. The objective of this study was to investigate the antimicrobial activity of R‑car and S‑car with gentamicin (GET) against methicillin‑resistant Staphylococcus aureus (MRSA). MRSA is a major human pathogen that causes serious problems, including hospital‑acquired pneumonia, abscesses and surgical wound infections. Nosocomial MRSA infections often exhibit multidrug resistance. In the present study, antimicrobial susceptibility testing was performed with R‑car, S‑car and GET using the broth microdilution method. Minimal inhibitory concentration values for R‑ and S‑car against six different strains of S. aureus ranged between 500 and 1,000 µg/ml. Anti‑MRSA activity was evaluated using the checkerboard and time‑kill assays to investigate the potential synergistic effects of different combinations of the carvone enantiomers and GET. R‑car plus S‑car, R‑car plus GET and S‑car plus GET exhibited significant synergistic activity against MRSA. These findings suggest that the single‑agent anti‑MRSA activities of R‑car, S‑car and GET are effectively increased through combination therapy. This study showed that carvone may be a potential adjuvant antimicrobial agent.