Synergistic effects of oxyresveratrol in conjunction with antibiotics against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a serious clinical problem worldwide. The aim of the present study was to examine the antimicrobial activity of oxyresveratrol (ORV) against MRSA. The antimicrobial activity of ORV was evaluated against three strains of MRSA and one methicillin-susceptible S. aureus (MSSA) strain using a minimal inhibitory concentration (MIC) assay, MTT colorimetric assay, checkerboard dilution test and time-kill assay. The MIC of ORV for all strains was moderate at 125 μg/ml. Of note, the antimicrobial activity and fractional inhibitory concentration index values of ORV were markedly increased in the presence of a non-growth inhibitory dose of certain antibiotics. Time-kill curves revealed that a combination of ORV with ciprofloxacin or with gentamicin reduced bacterial counts to below the lowest detectable limit after 24 h. These effective combinations may be used as potential antimicrobial regimens for use in the management of MRSA.