en Bacteriology Research (Original) <span style="font-size:11pt"><span style="unicode-bidi:embed"><span style="font-family:Calibri,sans-serif"><b><span new="" roman="" style="font-family:" times=""><span style="color:#002060"><span style="letter-spacing:.1pt">Introduction: </span></span></span></b><span new="" roman="" style="font-family:" times="">Medicinal plants have had a special value and importance in providing health and wellness of communities both in terms of treatment and prevention of diseases. The aim of this research was to investigate the antimicrobial activity of different extracts (aqueous, ethanolic, and methanolic) of two types of <i>Echium </i>(<i>Helioteropium ellipticum </i>and<i> Anchusa strigosa</i>)<i> </i>on <i>Staphylococcus aureus</i>, <i>Bacillus Cereus</i>, <i>Escherichia Coli</i>, <i>Salmonella Typhi</i> and <i>Shigella</i> dysentery bacteria.<span style="letter-spacing:.1pt"></span></span></span></span></span><br> <span style="font-size:12pt"><span new="" roman="" style="font-family:" times=""><b><span style="font-size:11.0pt"><span style="color:#002060">Material and Methods:</span></span></b> <span style="font-size:11.0pt">Extracts were prepared by soaking method. Antimicrobial activity was determined by two methods: dilution sequence in liquid medium and diffusion from disk in solid medium. The data were analyzed with SPSS24 software.</span><span style="font-size:11.0pt"></span></span></span><br> <span style="font-size:11pt"><span style="unicode-bidi:embed"><span style="font-family:Calibri,sans-serif"><b><span new="" roman="" style="font-family:" times=""><span style="color:#002060">Results:</span></span></b><span new="" roman="" style="font-family:" times=""> Gram-positive bacteria showed more sensitivity to the extracts than Gram-negative bacteria. Antimicrobial activity of <i>Heliotropium ellipticum</i> was more than <i>Anchusa strigosa</i>. Aqueous extract has the lowest and ethanolic extract has the highest antimicrobial activity. <i>Staphylococcus aureus</i> showed the highest and <i>Escherichia coli</i> the lowest sensitivity to the extracts. <i>Staphylococcus aureus</i> bacteria showed the largest diameter of non-growth aura (20.67 mm) at the concentration of 50 mg/ml of ethanolic extract, and the MIC of <i>Staphylococcus aureus</i> had the highest sensitivity at 312.5 PPM dilution</span><span new="" roman="" style="font-family:" times="">.</span></span></span></span><br> <b><span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times=""><span style="color:#002060"><span style="letter-spacing:-.1pt">Conclusion:</span></span></span></span></b> <span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times=""><span style="letter-spacing:-.1pt">T</span></span></span><span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times="">he two tested species have good antimicrobial activity and they can be used as natural substitutes for chemical antimicrobial agents.</span></span> Key words: Echium amoenum, gram positive bacteria, gram negative bacteria, antimicrobial activity. 18 24 http://tbsrj.mazums.ac.ir/browse.php?a_code=A-10-3572-1&slc_lang=en&sid=1 Masoud Kavehei masoudkavehei@gmail.com 100319475328460031114 100319475328460031114 No Department of Biology, School of Basic Sciences, Islamic Azad University, Borujerd Branch, Borujerd, Iran Seyed Hasan Sefidroo armansefidroo9@gmail.com 100319475328460031115 0009-0008-9893-9185 Yes Department of Biology, School of Sciences, University of Guilan, Rasht, Iran