Inhibition of Drug-resistant Staphylococcus aureus by Antibiotics Combined with Resveratrol and Quercetin Isomers

In order to explore the inhibitory effect of combination therapy on methicillin-resistant Staphylococcus aureus(MRSA),polygonum cuspidatum resveratrol and quercetin isomer were combined with antibiotics(erythromycin,oxacillin and ciprofloxacin)in this work,the antibacterial experiment,bactericidal curve and cytotoxicity test were carried out. Results showed that erythromycin combined with polygonum cuspidatum resveratrol or quercetin isomers could not enhance the antibacterial activity,and even showed the irrelevant or drug antagonistic effects. However,resveratrol or quercetin isomers associated with oxacillin or ciprofloxacin could enhance the antibacterial effect of antibiotics on MRSA,and respectively reduce the dosage of antibiotics by 50% and 75%. The best antimicrobial combination was quercetin isomer combined with ciprofloxacin(750 mg/L+25 mg/L),the fractional inhibitory concentration index(FIC)was 0.5,which suggested that it was a synergistic effect. However,the oxacillin or ciprofloxacin associated with quercetin isomer,which compared with the antibiotics alone,showing the weak cytotoxicity to mouse cells,cell viability was decreased by 7.2%~8.9%,while it was non-toxic increased to the oxacillin or ciprofloxacin combined with resveratrol. Therefore,polygonum cuspidatum resveratrol and quercetin isomers could be used as antibiotic enhancers of oxacillin or ciprofloxacin.