Plumbagin disrupts the mature biofilm of Staphylococcus aureus

Plumbagin, also known as 5-hydroxy-2-methyl-1,4-naphthoquinone (PLB), is a naturally occurring naphthoquinone molecule that has demonstrated strong antibacterial and antibiofilm properties against Staphylococcus aureus (S. aureus). However, the potential of PLB to eradicate mature biofilms and the underlying mechanisms involved remain unclear. In this study explored the effects of PLB on disrupting mature S. aureus biofilms, focusing on its impact on the extracellular polymeric substances (EPS) and potential mechanisms of action. Crystal violet (CV) and XTT assays demonstrated that PLB significantly reduced both the biomass and metabolic activity of mature S. aureus biofilms in a concentration-dependent manner. High-content screening (HCS) imaging demonstrated that PLB treatment induced significant alterations in the biofilm EPS architecture, leading to a substantial reduction in overall biomass and average thickness, with disruption severity correlating positively with PLB concentration. Using molecular fluorescence probing techniques, this study found that treatment with PLB resulted in a marked reduction in EPS components, including extracellular polysaccharides (PIA), proteins, and extracellular DNA (eDNA), compared to untreated controls. Molecular docking analysis revealed that PLB strongly interacts with several key S. aureus proteins involved in EPS production, such as IcaA, IcaD, IcaB, IcaC, Bap, ClfB, and CidA, particularly binding strongly to the active sites of IcaA and Bap. Furthermore, gene expression analysis indicated that PLB downregulated genes associated with biofilm EPS production. Overall, these findings suggest that PLB effectively disrupts S. aureus biofilms by targeting the EPS. These results highlight PLB as a promising candidate for targeting mature S. aureus biofilms in chronic infections.