Lemon Oils Attenuate the Pathogenicity of Pseudomonas aeruginosa by Quorum Sensing Inhibition

Abstract

The chemical composition of three <i>Citrus limon</i> oils: lemon essential oil (LEO), lemon terpenes (LT) and lemon essence (LE), and their influence in the virulence factors production and motility (swarming and swimming) of two <i>Pseudomonas aeruginosa</i> strains (ATCC 27853 and a multidrug-resistant HT5) were investigated. The main compound, limonene, was also tested in biological assays. Eighty-four compounds, accounting for a relative peak area of 99.23%, 98.58% and 99.64%, were identified by GC/MS. Limonene (59-60%), <i>γ</i>-terpinene (10-11%) and <i>β</i>-pinene (7-15%) were the main compounds. All lemon oils inhibited specific biofilm production and bacterial metabolic activities into biofilm in a dose-dependent manner (20-65%, in the range of 0.1-4 mg mL^-1) of both strains. Besides, all samples inhibited about 50% of the elastase activity at 0.1 mg mL^-1. Pyocyanin biosynthesis decreases until 64% (0.1-4 mg mL^-1) for both strains. Swarming motility of <i>P. aeruginosa</i> ATCC 27853 was completely inhibited by 2 mg mL^-1 of lemon oils. Furthermore, a decrease (29-55%, 0.1-4 mg mL^-1) in the synthesis of Quorum sensing (QS) signals was observed. The oils showed higher biological activities than limonene. Hence, their ability to control the biofilm of <i>P. aeruginosa</i> and reduce the production of virulence factors regulated by QS makes lemon oils good candidates to be applied as preservatives in the food processing industry.