fa fish disease fish disease پژوهشي Orginal research papers <p dir="ltr" style="text-align: justify;">In the present study bacterioph<a name="_GoBack"></a>ages isolated from rainbow trout farms and sewage treatment plants were genetically identified and their effectiveness on <em>Yersinia ruckeri </em>isolates from clinical cases of red mouth disease was investigated.&nbsp; Fish samples suspected to red mouth disease were collected from rainbow trout farms located in west Azerbaijan. <em>Y. ruckeri</em>, the causative agent of red mouth disease was initially identified using biochemical tests. The biotypes of all <em>Y. ruckeri</em> isolates were determined and their identity was confirmed by employing genus specific primers. Antimicrobial resistance of <em>Y. ruckeri</em> isolates were examined using common antibiotics in use in aquaculture. In order to isolating lytic bacteriophages, environmental samples mainly from rainbow trout farms and sewage treatment plants were collected in a period of six months. Isolated bacteriophages were titrated using two-layer agar method and their bactericidal effects were examined. For molecular characterization of bacteriophages, genomic DNA was extracted. Extracted genomic DNA from bacteriophages was digested using <em>Msp</em>I endonuclease. The results revealed that 4.48% of examined fish were positive for <em>Y. ruckeri.</em>&nbsp; Bacteriophages isolated from urban sewage treatment plants were effective on <em>Y. ruckeri</em> isolates. Maragheh and Urmia sewage treatment plants had the maximum and minimum phage titers, respectively. The genomic DNA of all isolated phages were smaller than genomic DNA of <em>Lambda</em> phage and all examined phages showed similar genomic DNA digestion patterns. It was concluded that sewage treatment plants could be an important source for phages effective on <em>Y. ruckeri </em>and maybe other aquaculture bacterial pathogens.&nbsp;&nbsp;</p> Bacteriophage, Rainbow trout, Redmouth disease, Wastewater, Yersinia ruckeri 267 280 http://jifro.ir/browse.php?a_code=A-10-1272-166&slc_lang=fa&sid=1 S. Ahmadpour 100319475328460015266 100319475328460015266 No K. Mardani 100319475328460015267 100319475328460015267 No A. Tukmechi a.tukmachi@urmia.ac.ir 100319475328460015268 100319475328460015268 Yes