Downregulation of quorum sensing genes in biofilm producing water-borne pathogen, Pseudomonas aeruginosa, by fatty acid isolated from Piper betel leaves

Abstract

Pseudomonas aeruginosa is highly versatile in adapting and surviving the harsh environment of the water purification system where an extensive treatment and disinfection processes occur rigorously. P. aeruginosa versatility is primarily contributed by its multifactorial, quorum sensing network. Additionally, P. aeruginosa is a major nosocomial pathogen with a global concern over its acquired resistant to multiple antibiotics. This alarming situation prompted for a more sensible approaches in exploring for novel anti-infective compounds that not only resolve the diseases but also mitigate the antimicrobial resistant in this water-borne pathogen. In this study, we identified a group of fatty acids isolated from Piper betel leaves; namely palmitic acid, 9, 12-octadecenoic acid, 7-octadecenoic acid and stearic acid; accounted for 65% of the sample size. We investigated the effect of the fatty acids on the expression level of the quorum sensing genes of P. aeruginosa from the las and the rhl domains. When grown with fatty acids at 100 μg/L, all tested genes showed a significant reduction in their expression by almost half, as compared to the control group. With a disturbed quorum sensing mechanism, the production of the virulence factors; namely elastase, protease, pyocyanin and pyoverdine; in fatty acids treated P. aeruginosa were correspondingly decreased. Morphology of formed biofilm by P. aeruginosa was notably distorted and reduced by 30% in the treated group. The work presented suggests plant-derived fatty acids as an alternative therapeutic agent as opposed to antibiotics due to its ability to inhibit the quorum sensing system in P. aeruginosa, with an advantage of less possibility in inducing drug resistance in the water-borne pathogen.