en ميکروب شناسي Microbiology Research Article Research Article <h1 style="text-align: justify;"><span style="font-size:12px;"><span style="font-family:Tahoma;"><strong>Background and objectives: </strong>Medicinal plants have long been considered as one of the most important pillars of traditional medicine. Existing challenges in the treatment of diseases, particularly infectious diseases, are major drivers for herbal medicine studies<span dir="RTL">.</span><em> Tribulus terrestris</em> has been widely used in traditional medicine to treat various diseases. This study aimed to investigate in vitro antibacterial effect of the aqueous extract of <em>T. terrestris</em> on several oral bacteria.</span></span></h1> <h1 style="text-align: justify;"><span style="font-size:12px;"><span style="font-family:Tahoma;"><strong>Methods:</strong> In this experimental study, after preparing the aqueous extract of <em>T. terrestris</em>, minimum inhibitory and bactericidal concentrations (MIC and MBC) of the extract were determined against standard strains of <em>Streptococcus mutans</em>, <em>Staphylococcus aureus</em>, <em>Klebsiella pneumoniae</em> and <em>Streptococcus pyogenes </em>using the broth microdilution method. The experiments were repeated three times and the results were analyzed with SPSS 22 using the one-way analysis of variance (ANOVA) and LSD statistical tests with the significance level set at 0.05.</span></span></h1> <div style="text-align: justify;"><span style="font-size:12px;"><span style="font-family:Tahoma;"><strong>Results: </strong>The aqueous extract of <em>T. terrestris </em>had the highest inhibitory effect on <em>S. pyogenes</em> and <em>S. mutans</em>, and the difference between the MIC and MBC values was significant (P <0.05). However, no such effect was observed against <em>S. aureus</em> and <em>K. pneumonia</em> at concentrations below 50 mg/ml when compared to ampicillin and chlorhexidine.<br> <strong>Conclusion: </strong>The aqueous extract of <em>T. terrestris </em>has significant antibacterial effects against <em>S. pyogenes</em> and <em>S. mutans</em>. Therefore, it can be incorporated into topical formulations such as toothpaste and mouthwash products after further in vivo and toxicity experiments.</span></span></div> Tribulus,Anti-Bacterial Agents,bacteria, 7 12 http://mlj.goums.ac.ir/browse.php?a_code=A-10-56-2&slc_lang=en&sid=1 Zahra Kiani kiani.za@gmail.com 100319475328460021015 100319475328460021015 No Pharmacology department, Faculty of Pharmacy, Birjand University of Medical Sciences, Birjand, Iran Pouria Mohammad Parast Tabas pouriamp1377@gmail.com 100319475328460021016 100319475328460021016 No Student Research Committee, BSc Student in Medical Laboratory Science, Birjand University of Medical Sciences, Birjand, Iran khashayar khalilpour khashayar.khalilpour@yahoo.com 100319475328460021017 100319475328460021017 No Faculty of Dentistry, Birjand University of Medical Science, Birjand, Iran Mahjoube Goldani Moghadam Mahdjoube.gm@gmail.com 100319475328460021018 100319475328460021018 No Orthodontic Department, Faculty of Dentistry, Birjand University of Medical Sciences, Birjand, Iran Majid Zare_Bidaki m.zare@live.co.uk 100319475328460021019 100319475328460021019 Yes Infectious Diseases Research Center, Birjand University of Medical Sciences, Birjand, Iran