Eliminating extracellular autoinducing peptide signals inhibits the Staphylococcus aureus quorum sensing agr system

Abstract

An accessory gene regulator (agr) in the quorum sensing (QS) system in Staphylococcus aureus contributes to host infection, virulence factor production, and resistance to oxidative damage. Artificially maintaining the inactive state of agr QS impedes the host infection strategy of S. aureus and inhibits toxin production. The QS system performs intercellular signal transduction, which is activated by the mature autoinducer peptide (AIP). It is released from cells after AgrD peptide processing as an intercellular signal associated with increased bacterial cell density. This study evaluated the effectiveness of inhibiting agr QS wherein AIP trap carriers were made to coexist when culturing Staphylococcus aureus. Immersing a nitrocellulose (NC) membrane in Staphylococcus aureus ATCC 12600 culture inhibited QS-dependent α-hemolysin production, which significantly reduced the hemolysis ratio of sheep red blood cells by the culture supernatant. A quartz crystal microbalance analysis supported AIP adsorption onto the NC membrane. Adding the NC membrane during culture was found to maintain the expression levels of the agr QS gene agrA and α-hemolysin gene hla lower than that when it was not added. Eliminating extracellular AIP signals allowed agr QS to remain inactive and prevented QS-dependent α-hemolysin expression. Isolating intercellular signals secreted outside the cell is an effective strategy to suppress gene expression in bacterial cells that collaborate via intercellular signaling.