Targeting Autoinducer-2 Quorum Sensing: Novel Inhibitors Attenuate Virulence in Staphylococcus aureus and Pseudomonas aeruginosa

Antibiotic overuse has driven the development of bacterial drug resistance, highlighting the urgent need for new antimicrobial strategies. Quorum sensing, particularly via autoinducer-2 (AI-2) signal molecules, is a bacterial communication system involved in the development of drug resistance. Our recent work identified AI-2 inhibitors that disrupt biofilm formation in Staphylococcus aureus and Pseudomonas aeruginosa. Here, we investigated the efficacy of the three most promising compounds in modulating bacterial virulence. The compounds strongly impaired the bacterial ability to adhere to human epithelial cells. ELISA-based assays and Western blot analyses revealed the efficacy of the compounds in controlling S. aureus virulence by decreasing the levels of bacterial adhesins, α-hemolysin, and protein SpA. In a co-culture with S. aureus, colorimetric assays revealed the compound efficacy in decreasing P. aeruginosa pyocyanin and elastase production in a dose-dependent manner. Importantly, no cytotoxicity was observed both in vitro (A549 cells) and in vivo (Galleria mellonella model). These results support the potential of our compounds to modulate virulence factor expression consistent with quorum-sensing disruption as promising candidates for the treatment of multidrug-resistant infections.