Inhibitory effect of paeoniflorin on the LuxS/AI-2 quorum sensing system and the virulence of <i>Glaesserella parasuis</i>

Glaesserella parasuis, the causative agent responsible for Glässer's disease in swine, leads to severe polyserositis, meningitis, and arthritis, posing a significant threat to swine production. The LuxS/AI-2 quorum sensing system is crucial for G. parasuis growth, biofilm formation, and pathogenicity. Quorum sensing inhibitors, such as paeoniflorin (PF), offer a potential strategy to mitigate antibiotic resistance. This study evaluated PF's effects, alone and combined with antibiotics, on quorum sensing, biofilm formation, and virulence gene expression of drug-resistant G. parasuis. PF significantly reduced AI-2 production, biofilm formation, and virulence genes expression in vitro. A viable model for G. parasuis infection was established using KM mice, and demonstrated that a low-dose combination of PF and lincomycin effectively mitigated organ damage, reduced bacterial load in the liver, and improved survival rates compared to individual treatments in vivo. These findings suggest PF as a promising quorum sensing and virulence inhibitor for controlling G. parasuis infections. Further research is warranted to optimize its clinical application.