Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 11 1 2019 03 23 55 59 EN Davoud Iman Islamieh Department of Microbiology and Applied Microbiology Research Center, Systems Biology and Poisonings Institute and Applied Virology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran Davoud Afshar Department of Microbiology and Virology, School of Medicine, Zanjan University of Medical Sciences, Zanjan, Iran Davoud Esmaeili Department of Microbiology and Applied Microbiology Research Center, Systems Biology and Poisonings Institute and Applied Virology Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran 2018 03 06 2019 02 20 Background and Objectives: Expressions of lasA and lasB genes of Pseudomonas aeruginosa are associated with bacterium pathogenicity. The present study was aimed to assess the effect of Satureja khuzistanica essential oil (SKEO) extract on expression of lasA and lasB genes in P. aeruginosa. Materials and Methods: Pseudomonas aeruginosa isolates were cultured in Mueller Hinton broth containing sub-inhibitory concentrations of SKEO and total RNA extracted using Trizol method. cDNA was synthesized using random Hexamer primer and finally the expression of lasA and lasB genes carried out by real-time PCR. Results: The MICs of SKEO extract for PA9, PA10, PA11, PA13, PA41 and PA42 isolates were 8, 8, 8, 9, 7 and 12 µg/ml, respectively. Statistical analysis for 6 isolates revealed that the reduction in expression of lasA and lasB genes under SKEO treatment was significant (P<0.05). Conclusion: The insignificantly increasing of lasB gene expression may lead to low virulent strains, for probably reason that the strain’s exotoxin A are destroyed in the high amount of protease. In conclusion, using of SKEO in burned patients infected with P. aeruginosa may be effective; however, it is better to assess the spectrum activity of SKEO, pharmacokinetics, potency and its toxicity in human cells. https://ijm.tums.ac.ir/index.php/ijm/article/view/1670 https://ijm.tums.ac.ir/index.php/ijm/article/download/1670/1112