en تخصصي Special Original article Original article <p><font face="times new roman,times,serif" size="2"><b>Background:</b> In current study, chemical composition and antibacterial activity of leaves and flowers essential oils of <i>Origanum vulgare</i> ssp. gracile against four food-borne pathogens including&nbsp;<i>&nbsp;</i></font><font face="times new roman,times,serif" size="2"><i>Escherichia coli</i></font><font face="times new roman,times,serif" size="2">, <i>Listeria monocytogenes</i>, <i>Salmonella thyphimurium</i> and <i>Staphylococcus aureus</i> were examined.<br> <b>Methods:</b> The different organs (leaves and flowers) of <i>O. vulgare</i> ssp. gracile were harvested at flowering stage from wild grown plants in Kurdistan province, Iran. Phytochemical properties of the essential oils were identified by GC and GC/MS analysis. Also, antibacterial effects of <i>O. vulgare</i> ssp. gracile against each bacterial strain were detected by calculating the minimum inhibitory concentration and minimum bactericidal concentration using micro-dilution method. Data was analyzed by chi square and fisher exact tests using SPSS 16.0.<br> <b>Results:</b> Main components of leaf and flower oils were carvacrol (46.5% and 60.6%), &gamma;-terpinene (13.91% and 16.64%) and &rho;-cymene (13.54% and 7.21%). <i>E. coli</i> and<i> S. aureus</i> had similar sensitivity to essential oils, but <i>S. typhimurium</i> showed more sensitivity. Output of composition analysis showed that the <i>O. vulgare</i> ssp. gracile flowers essential oil has more effect than those from leaves.<br> <b>Conclusion: </b>This work showed substantial inhibitory effect of <i>O. vulgare</i> ssp. gracile essential oils on food-borne pathogens. The efficiency of <i>O. vulgare</i> ssp. gracile flowers oils in reduction of the bacterial activity was higher than the leaves essential oils. According to the results of this research, this essential oil can be utilized as a natural preservative in food products. </font></p> Origanum, Phytochemicals, Anti-Bacterial Agents 120 124 http://jfqhc.ssu.ac.ir/browse.php?a_code=A-10-1-45&slc_lang=en&sid=1 M. Moradi No A. Hassani No A. Ehsani No M. Hashemi mo_hashemi@hotmail.com Yes Department of Nutrition, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran M. Raeisi No S.S. Naghibi No