The effects of sub-inhibitory concentrations of some essential oils on adherence, motility, alginate production and biofilm formation in Pseudomonas aeruginosa

Pseudomonas aeruginosa is an important opportunistic pathogen with many virulence factors. In this study, the effects of sub-MICs of three essential oils on alginate production, biofilm formation, swimming, twitching and adhesion in P. aeruginosa have been evaluated. The plants (Zataria multiflora Boiss., Myrtus communis L. and Eucalyptus camaldulensis Dehnh.) were dried in shadow and were hydro-distilled for 90 minutes. Minimal inhibitory concentrations (MIC) of essential oils were determined by macrodilution method. The virulence factors in the mucoid P. aeruginosa 8821M were determined in the presence of sub-MICs (1/2, 1/4 and 1/8) of essential oils. The MICs of essential oils against P. aeruginosa for Z. multiflora, M. communis and E. camaldulensis oils were obtained 64, 64 and 64µg/mL, respectively. The results showed that all oils at 1/2 and 1/4 MICs significantly reduced all tested virulence factors. At 1/8 MICs, Z. multiflora oil had significantly reduced virulence factors, but another oils had different effects. This study showed that sub-MIC levels of Z. multiflora, M. communis and E. camaldulensis essential oils affected alginate production, biofilm formation, swimming, twitching and adhesion in P. aeruginosa and it is probable to use these medicinal plants for treating.