Isovanillin decreases the virulence regulated by the quorum sensing system of Pseudomonas aeruginosa.

The quorum-sensing (QS) system of Pseudomonas aeruginosa dominates the pathogenicity of the acute or chronic infection process. Hence, curbing the pathogenicity of P. aeruginosa by targeting QS system is an ideal strategy. This study aims to identify potential anti-virulence compounds that can effectively disrupt the QS system of P. aeruginosa using a combination of virtual screening and experimental validation techniques. We explored inhibitory effect of isovanillin obtained by virtual screening on P. aeruginosa QS regulated virulence factors extracellular protease, biofilm, and pyocyanin. Results displayed that isovanillin could inhibit the virulence phenotypes regulated by the las- and pqs-QS systems of P. aeruginosa. The synthesis of extracellular proteases, pyocyanin, and biofilm formation by P. aeruginosa were dramatically inhibited by sub-MICs doses of isovanillin. The results of RNA sequencing and quantitative PCR revealed that the QS-activated genes down-regulated by subinhibitory isovanillin in the transcriptional evels. Furthermore, the presence of isovanillin increased the susceptibility of drug-resistant P. aeruginosa to kanamycin, meropenem, and polymyxin B. Treatment of isovanillin as a monotherapy significantly decreased the mortality of C. elegans in P. aeruginosa PAO1 or UCBPP-PA14 (PA14) infection. Our study reported the anti-virulence activity of isovanillin against P. aeruginosa, and provided a structural foundation for developing anti-virulence drugs targeting the QS system of P. aeruginosa.