Flavone Reduces the Production of Virulence Factors, Staphyloxanthin and α-Hemolysin, in Staphylococcus aureus

Staphylococcus aureus is a leading cause of nosocomial infections due to its resistance to diverse antibiotics. This bacterium produces a large number of extracellular virulence factors that are closely associated with specific diseases. In this study, diverse plant flavonoids were investigated to identify a novel anti-virulence compound against two S. aureus strains. Flavone, a backbone compound of flavonoids, at subinhibitory concentration (50 μg/mL), markedly reduced the production of staphyloxanthin and α-hemolysin. This staphyloxanthin reduction rendered the S. aureus cells 100 times more vulnerable to hydrogen peroxide in the presence of flavone. In addition, flavone significantly decreased the hemolysis of human red blood by S. aureus, and the transcriptional level of α-hemolysin gene hla and a global regulator gene sae in S. aureus cells. This finding supported the usefulness of flavone as a potential antivirulence agent against antibiotic-resistant S. aureus.