en Microbial pathogenesis Microbial pathogenesis Original article Original article <p dir="ltr"><strong>Introduction:</strong> In this study, the chemical composition and antimicrobial activity of essential oil of<em> Ziziphora clinopodiodes </em>and its potential application as a natural preservative in reducing the indigenous microbial population of hamburger were investigated. <strong>Method: </strong>Essential oil of <em>Ziziphora clinopodiodes</em> cultivated in Iran was obtained by Hydro-distillation method (HDM). Chemical composition of the oil was determined by gas chromatography/mass spectrometry (GC-MS) analysis. Antimicrobial activity of the essential oil was checked against <em>Staphylococcus aureus</em>, <em>Escherichia coli</em>,<em> Bacillus subtilis</em>, <em>Salmonella typhi</em>, <em>Listeria monocytogenes</em>, <em>Pseudomonas aeruginosa</em>, by using Agar dilution method (ADM). Minimum Inhibitory Concentration (MIC) values of each active oil concentration were determined and its potential application as a natural preservative in reducing the indigenous microbial population of hamburger was investigated.<strong> Results:</strong> The major components were carvacrol (54.31%), thymol (12.51%), octadecane (9.51%) and pulegone (4.88%). The results showed a significant activity against the tested strains (gram-positive and gram-negative bacteria). Addition of essential oil in concentration higher than MIC values reduced the microbial population of hamburgers stored at 25&deg;C, 4&deg;C and -12&deg;C. In samples refrigerated at 4&deg;C, differences between the controls and samples treated with essential oil at MIC values (0.20 and 0.4 mg/ml)&nbsp; were&nbsp; not&nbsp; significant&nbsp; during the first 24 h (<em>p></em> 0.05), but higher concentration of essential oil resulted in about 2 to 3 log reduction in total microorganisms. <strong>Conclusion: </strong>This study showed that the <em>Ziziphora clinopodiodes</em> essential oil can be added to the ingredients of foods as the natural antibacterial agent.</p> Essential oil, Ziziphora clinopodiodes, Minimum Inhibitory Concentration 138 142 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-73-1&slc_lang=en&sid=1 Anousheh Sharifan rahmanish3@mums.ac.ir Yes Department of Food Science and Technology, Islamic Azad University, Science and Research Branch, Tehran, Iran Leila Beikmohammadi a@a.com No Ph.D. student, Department of Molecular Medicine, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran