Effective Inhibition and Eradication of Pseudomonas aeruginosa Biofilms by Satureja khuzistanica Essential Oil Nanoemulsion

Abstract The application of essential oil nanoemulsions (EO-nano) are growing to overcome the serious problem of bacterial resistance. Pseudomonas aeruginosa as a pathogenic bacterium could form biofilms which resist antibiotics and leads to serious infections in hospitals and microbial contaminations in industrial settings. In this research, five different nanoemulsions prepared from Lavandula angustifolia, Rosmarinus officinalis and Satureja khuzistanica essential oils (SKEO) and two EO constituents (carvacrol and 1,8-cineol) were prepared and characterized. The formulations showed noticeable long term stability according droplet size measurements using Dynamic light scattering instrument. Then, the antibacterial activity of EOs and their formulations were evaluated with micro dilution assay against Pseudomonas aeruginosa PAO1. The results showed that nanoemulsions could improve the antibacterial activity of EOs between 4 to 8 times compared to bulk oils. Sub-MIC concentrations of nanoemulsions and bulk oils were then evaluated for eradication and prevention of PAO1 biofilm formation. Carvacrol rich SKEO nanoemulsion with 89.53±4.88% inhibition and 56.65±7.65% eradication effect had the best results among the all tested formulations and bulk oils. Furthermore, the inhibitory effect of the SKEO nano formulation on the pyocyanin production exhibited up to 89.44±3.41% decrease in the production of this virulence factor. These results indicated the potential use of SKEO nano formulation as antibacterial and antibiofilm agent.