Effects of Sub-Minimal Inhibitory Concentrations of Some Essential Oils on Virulence Factors of Pseudomonas aeruginosa

Abstract

Pseudomans aeruginosa, an opportunistic pathogen that produces a number of unique virulence factors causes severe and life-threatening infections. In this study the effects of sub-minimal inhibitory concentrations (sub-MICs) of some essential oils on virulence factors of Pseudomonas aeruginosa such as alginate production, biofilm formation, swimming, twitching and adhesion were evaluated. MIC of Zataria multiflora, Myrtus communis, Eucalyptus camaldulensis, Mentha spicata and Cumminum cyminum essential oils on mucoid P. aeruginosa 8821M were determined by macrodilution method. Alginate production, biofilm formation, swimming, twitching and adhesion in the present of sub-MICs (1/2, 1/4 and 1/8 MIC) of essential oils were determined. GC-MS analysis led to identification of 32, 21, 22, 15 and 32 components in Myrtus communis, Eucalyptus camaldulensis, Zataria multiflora, Mentha spicata and Cumminum cyminum oils respectively. The MICs of essential oils against P. aeruginosa for Z. multiflora, M. communis, E. camaldulensis, M.spicata and C. cyminum oils were obtained 64, 64, 64,16 and 32μ.g/ml respectively. The results show that all oils at 1/2 and 1/4 MICs were significantly reduced all tested virulence factors. At 1/8 MICs, Z. multiflora oil had significantly reduced all virulence factors, but another oils had different effects. This study showed that sub-MIC levels of Z. multiflora, M. communis, E. camaldulensis, M. spicata and C. cyminum essential oils affected alginate production, biofilm formation, swimming, twitching and adhesion in P. aeruginosa and it is probable to use of these medicinal plants for treating.