en Other Other Original article Original article <p dir="ltr"><strong><span style="font-family:garamond,serif;"><span style="font-size:10.0pt;">Introduction:</span></span></strong><span style="font-family:garamond,serif;"><span style="font-size:10.0pt;"> The aim of this study was to characterize the chemical composition and antimicrobial activity of <em>Trachyspermum copticum </em>essential oil (EO).<strong> Methods:</strong> The chemical composition of seed samples obtained from Mianeh city in East Azerbaijan, was assessed using gas chromatography-mass spectrometry (GC-MS). The antimicrobial activity was evaluated by disc diffusion method against methicillin-resistant <em>Staphylococcus aureus</em> (MRSA), other extended-spectrum beta-lactamases (ESBLs) producing, as well as Gram-negative and Gram-positive bacteria. The minimum inhibitory concentration (MIC) value of EO was assessed using agar dilution method. <strong>Results:</strong> Thirteen monoterpene hydrocarbons (57.6%) and oxygenated monoterpenes (42.4%) compounds were identified in the EO, of which, 3 compounds, including thymol, m-cymene, and, &gamma;-terpinene were the major components of the EO with quantities of 41.9, 33.53, and 20.42%, respectively. The EO showed antimicrobial activity against ten microorganisms, especially <em>Streptococcus sanguis</em>, <em>S. aureus </em>(MRSA strain), and <em>Klebsiella pneumoniae</em> (ESBL-producing strain), which was potentially better than tetracycline and kanamycin. <strong>Conclusion: </strong>This study confirmed that EO of<em> T. copticum</em> has <em>in vitro</em> antimicrobial activity against Gram-negative and Gram-positive bacteria, which has made it an alternative antibacterial agent.</span></span></p> Phytochemicals, Trachyspermum copticum, Essential Oil 71 74 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-54-2&slc_lang=en&sid=1 Haedeh Mobaiyen drhmobaiyen@gmail.com Yes Department of Microbiology, Tabriz branch, Islamic Azad University, Tabriz, Iran. Maisam Nasarollah Pour : maisam_nasrollahpour@yahoo.com No Department of Microbiology, Tabriz branch, Islamic Azad University, Tabriz, Iran. Franak Elmi elmibiosys@yahoo.com No Department of Biology, Marand branch, Islamic Azad University, Marand, Iran.