Aquilaria sinensis essential oil inhibits biofilm formation and virulence of Staphylococcus aureus

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Abstract
Staphylococcus aureus is a major foodborne pathogen characterized by strong virulence and biofilm-forming ability, posing a persistent threat to food safety. Aquilaria sinensis (Lour.) Gilg, a medicinal and edible plant found in tropical regions such as Hainan, has rarely been investigated for its quorum-sensing inhibitory (QSI) potential. In this study, four types of A. sinensis essential oils were systematically evaluated for their ability to inhibit quorum sensing and related virulence in S. aureus . Among them, the Tong-Ti-Xiang type supercritical essential oil (TTC) exhibited the strongest activity. At a sub-inhibitory concentration of 125 μg/mL (1/4 MIC), TTC reduced biofilm formation by up to 78% without affecting bacterial growth. Confocal laser scanning Microscopy and scanning electron microscopy analyses further confirmed that TTC compromised the density and structural integrity of the biofilms. Moreover, TTC suppressed α-hemolysin activity and significantly downregulated quorum-sensing-regulated genes involved in biofilm formation and adhesion, including icaA , icaD , clfA , clfB , and agrA . Gas chromatography mass spectrometry analysis revealed that TTC is rich in chromone derivatives, among which 2-phenethyl-4H-chromen-4-one showed strong binding affinity toward the adhesion-associated IcaA protein and the QS-associated AgrA protein in molecular docking analysis, suggesting it as a key active compound responsible for the observed QSI effect. Overall, these findings highlight TTC as a promising natural anti-biofilm and anti-virulence agent for controlling foodborne pathogens.

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