ASSESSMENT OF ANTIVIRULENCE ACTIVITY OF ESSENTIAL OILS AGAINST Pseudomonas aeruginosa

Abstract

Essential oils (EO) have been described as bactericidal agents; however, in vitro studies indicate that some of their volatile constituents at sublethal concentrations may inhibit or promote quorum sensing (QS) systems in Pseudomonas aeruginosa. It is necessary to explore the role that volatile mixtures can play on virulence and in the establishment of bacteria on in vivo systems. The study was carried out to evaluate the bactericidal and antivirulence properties of EO obtained from Thymus vulgaris L., Cymbopogon citratus (DC.) Stapf and Tagetes lucida (Cav) against P. aeruginosa. Antivirulence activity was assessed by the inhibition of factors regulated by QS, such as pyocyanin production and protease and elastase activity; in addition, the composition of volatiles and their ability to prevent the establishment of the infection in model of lesion in mice were determined. In vitro tests showed that T. vulgaris EO (TVEO) only exhibited bactericidal activity, and T. lucida EO (TLEO) reduced pyocyanin production by 58 % at a sublethal concentration of 200 μg mL^-1. In the case of the EO of C. citratus no bactericidal effect was registered at the maximum concentration evaluated (1000 μg mL^-1), although it slightly reduced the pyocyanin production (30 %). In the in vivo studies only the TLEO and Neosporin® (positive control) interfered in the establishment of the bacteria, while the TVEO, contrary to the expected, favored the establishment of the bacterium, mainly in areas adjacent to the lesions. A positive correlation was observed between the establishment of the bacteria and the number of constituents present in the EO. These results support the use of the EO evaluated to combat P. aeruginosa and their possible application in anti-virulence therapies.