AimsThe study aimed to perform a systematic investigation of the effects of quercetin on biofilm formation and virulence factors in Pseudomonas aeruginosa. Methods and ResultsThe Ps.aeruginosa strain PAO1 was selected as the test strain. The results indicated that quercetin did not impact the growth of PAO1 as determined by MIC and growth curve analysis. However, this compound significantly inhibited (P<005) biofilm formation and production of virulence factors including pyocyanin, protease and elastase at a lower concentration than those for most previously reported plant extracts and substances. Considering the central role of quorum sensing (QS) in the regulation of biofilm and virulence factor, we further detected the transcriptional changes associated with QS and found that the expression levels of lasI, lasR, rhlI and rhlR were significantly reduced (P<005) by 34, 68, 57 and 50%, respectively, in response to 16gml(-1) quercetin. ConclusionsThis study indicated that quercetin is an effective inhibitor of biofilm formation and virulence factors in Ps.aeruginosa. Significance and Impact of the StudyThis is the first study to demonstrate that quercetin is an effective inhibitor of QS, biofilm formation and virulence factors in Ps.aeruginosa. Furthermore, quercetin might have potential in fighting biofilm-related infections.