Variation in synergistic activity by flavone and its related compounds on the increased susceptibility of various strains of methicillin-resistant Staphylococcus aureus to beta-lactam antibiotics.

We found that some flavonoids had a weak antibacterial effect on methicillin-resistant Staphylococcus aureus (MRSA), but that at sub-MIC concentrations they greatly increased the susceptibility of these strains to beta-lactam antibiotics. Flavone showed diverse synergistic effects on the susceptibility of MRSA to beta-lactam antibiotics. The variation of the synergistic effects of the flavones to increase the susceptibility of strains of MRSA to beta-lactam antibiotics coincided with their varying effects on growth-inhibition of these strains. Based on these findings, we have proposed a model for the mechanisms of high resistance of MRSA to beta-lactams and the massive reduction in the beta-lactams MIC caused by flavones.