Effects of Sub-inhibitory Concentrations of Essential Oils of Mentha spicata and Cumminum cyminum on Virulence Factors of Pseudomonas aeruginosa

  Background : Pseudomonas aeruginosa is one of important opportunistic pathogen, that cases serious infections . It produces many virulence factors, and this bacterium usually is resistance against antimicrobial agents.   Objective :The aim of this study was evaluate the effects of sub-MICs of essential oils of Mentha spicata and Cumminum cyminum on alginate production, biofilm formation, swimming, twitching and adhesion in P. aeruginosa 8821M.   Method : Minimal inhibitory concentrations (MIC) of essential oils of Mentha spicata and Cumminum cyminum 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 in mucoid P. aeruginosa 8821M and compared with controls.   Results : The MICs of essential oils against P. aeruginosa for M. spicata and C. cyminum oils were obtained 16 and 32 μg/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, M. spicata had effect just on adhesion but C. cyminum had effect on Alginate production, biofilm formation, swimming and twitching . Conclusion : This study showed that sub-MIC levels of M. spicata and C. cyminum essential oils affected alginate production, biofilm formation, swimming, twitching and adhesion in P. aeruginosa 8821M and it is probable to use of these medicinal plants for treating.