PHENOTYPIC AND MOLECULAR EVALUATION OF PSEUDOMONAS AERUGINOSA AND STAPHYLOCOCCUS AUREUS VIRULENCE PATTERNS IN THE PRESENCE OF SOME ESSENTIAL OILS AND THEIR MAJOR COMPOUNDS

This study reports the effect of some essential oils (EOs) and of some of their major fractions on soluble virulence factors and quorum sensing (QS) gene expression profiles of 15 Staphylococcus aureus and Pseudomonas aeruginosa clinical strains. EOs were extracted from various angiosperm and gymnosperm vegetal taxons by hydrodistillation in a Neo-Clevenger-type apparatus and characterized by measuring the density and refractive index, as well as by gas chromatographic analysis. EOs and their major components proved to inhibit the phenotypic expression of six soluble virulence determinants (haemolysins, gelatinase, DN-ase, lipase, amylase, esculin hydrolysis) when used in sub-inhibitory concentrations, in both P. aeruginosa and S. aureus strains. EOs extracted from Salvia officinalis, Rosmarinus officinalis, Abies alba and Eugenia caryophyllata as well as some of their major compounds (limonene, eugenol and eucalyptol) inhibited QS genes expression in S. aureus, while in P. aeruginosa only E. caryophyllata EO proved to inhibit both las and rhl QS genes expression. Our results demonstrate that essential oils are efficient candidates for developing novel ecological antimicrobial strategies aiming to attenuate the pathogenicity and virulence of opportunistic pathogens isolated from severe infections.