Senna alexandriana mill as a potential inhibitor for quorum sensing-controlled virulence factors and biofilm formation in Pseudomonas aeruginosa PAO1

Background: Senna alexandriana Mill is a medicinally important plant used in laxatives and also possesses potent antimicrobial compounds, but its effect on the Pseudomonas aeruginosa was never analyzed. Aim: This study was carried out with the objective to attenuate quorum sensing (QS)-controlled virulence factors in P. aeruginosa and its biofilm. Methods: In the present study, acetone and hexane extracts of S. alexandriana mill were tested at sub-minimum inhibitory concentration concentrations for their anti-QS activity using bioreporter strain the Chromobacterium violaceum CV026. The effect of S. alexandriana Mill on different virulence phenotypes such as pyocyanin and protease production was investigated. Finally, the effect of the extract on P. aeruginosa, biofilm formation was also determined using the spectrophotometry-based method and microscopic analysis. Results: The extracts were tested for their activities against QS-controlled virulence factors of P. aeruginosa at 600 μg/ml and 800 μg/ml acetone and hexane extract concentration, respectively. Results showed that both the extracts have an inhibitory effect on different virulence factors of P. aeruginosa, including pyocyanin, protease production, and biofilm formation, without affecting the growth. The P. aeruginosa biofilm was found to be decreased by 75% and 62% in acetone and hexane extract presence. Conclusion: The results revealed that both acetone and hexane extracts showed anti-biofilm and anti-QS activity. It depicted the potential of S. alexandriana Mill against P. aeruginosa infection, its biofilm, and QS.