en fish disease fish disease پژوهشي Orginal research papers <font face="Times New Roman" size="3"> </font><p class="MsoNormal" style="margin: 0cm 0cm 10pt text-align: justify line-height: 120%"><span style="font-family: "Times New Roman","serif" mso-ascii-theme-font: major-bidi mso-hansi-theme-font: major-bidi mso-bidi-theme-font: major-bidi"><font size="3">During the last decade, shrimp aquaculture has developed rapidly in many developing countries. Antibiotic resistance is a major problem in shrimp aquaculture. Seaweeds are considered as potent source of bioactive compounds that are able to produce biological activities. The aim of this study was to evaluate the antibacterial activity of ethanolic and chloroformic crude extracts of the brown algae, <i>Sargassum latifolium</i> derived from Persian Gulf waters. The extractions against shrimp selective pathogen bacteria including <i>Vibrio alginolyticus, V. parahaemolyticus </i>and <i>V. harveyi</i> were used by disk diffusion agar method.<i> </i>Results revealed that all mentioned bacteria were sensitive to both ethanolic and chloroformic crude extracts of <i>S.latifolium</i>. The minimum inhibitory concentration of chloroformic extract of <i>S. latifolium</i> against the bacteria was performed by tube dilution technique. MICs were 5, 10 and 10 mg ml</font>^{<font size="2">-1 </font>}<font size="3">for <i>V. alginolyticus, V. parahaemolyticus</i> and <i>V. harveyi</i>, respectively while minimum bactericidal concentrations (MBC) were 5, 15 and 20 mg ml</font>^{<font size="2">-1</font>}<font size="3">. This study recommended that <i>S.latifolium</i> isolated from Persian Gulf waters has antibacterial activity potential against shrimp pathogen bacteria.<b><o:p /></b></font></span></p><font face="Times New Roman" size="3"> </font> Antibacterial activity, Sargassum latifolium, Seaweed extract, Vibrio, Persian Gulf 765 775 http://jifro.ir/browse.php?a_code=A-10-1-198&slc_lang=en&sid=1 A. Dashtiannasab adashtiannasab@gmail.com 10031947532846004734 10031947532846004734 Yes S. Kakoolaki 10031947532846004735 10031947532846004735 No M. Sharif Rohani 10031947532846004736 10031947532846004736 No V. Yeganeh 10031947532846004737 10031947532846004737 No