en Microbiology Microbiology پژوهشي Research <div><strong>Introduction: </strong>Various microorganisms are involving in oral infections. Antimicrobial agents used against oral pathogens have side effects and can caused drug resistance. Eucalyptus is one of the most widely used plant with antimicrobial activity. Therefore, the aim of this study was to investigate the chemical composition and antimicrobial activity of <em>Eucalyptus camaldulensis</em> (<em>E. camaldulensis</em>) essential oil on dental caries pathogens includes <em>Streptococcus mutans </em>(<em>S. mutans</em>), <em>Lactobacillus rhamnosus </em>(<em>L. rhamnosus</em>), <em>Actinomyces viscosus</em> (<em>A. viscosus</em>), and <em>Candida albicans</em> (<em>C. albicans</em>).<br> <strong>Materials and methods: </strong>In this study, <em>E. camaldulensis</em> essential oil was prepared and its antimicrobial activity was evaluated by disk diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) methods on stablished terminology strains of <em>C. albicans</em>, <em>S. mutans</em>, <em>L. rhamnosus</em> and <em>A. viscosus</em>. Moreover, chemical composition of <em>E. camaldulensis</em> essential oil was evaluated by gas chromatography-mass spectrometry (GC-MS) method.<br> <strong>Results: </strong>Our results showed that the most antibacterial activity of <em>E. camaldulensis</em> essential oil was related to <em>L. rhamnosus</em>, <em>A. viscosus</em>, and <em>S. mutans</em>. Also, <em>E. camaldulensis</em> essential oil showed an appropriate antifungal activity against <em>C. albicans</em>. The dominant chemical composition of <em>E. camaldulensis</em> essential oil was 1,8-cineole (36.62%).<br> <strong>Conclusion: </strong>In general, <em>E. camaldulensis</em> essential oil has an appropriate antifungal and antibacterial activity against oral pathogens. Therefore, it can be use in pharmaceutical industry to produce antimicrobial agents against dental caries and oral infectious diseases.</div> Oral infection, Oral pathogens, Antimicrobial activity, Essential oil, Eucalyptus 43 49 http://jbrms.medilam.ac.ir/browse.php?a_code=A-10-452-2&slc_lang=en&sid=1 Rasoul Etemadi etemadi-ayda@yahoo.com 10031947532846003671 10031947532846003671 No Department of Orthodontics, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran Parisa Moghadam pmogadam1120@gmail.com 10031947532846003672 10031947532846003672 Yes Department of Microbiology, Urmia Branch, Islamic Azad University, Urmia, Iran Farnaz Yousefi raheleh.yousefi@gmail.com 10031947532846003673 10031947532846003673 No Department of Microbiology, Urmia Branch, Islamic Azad University, Urmia, Iran