Location: Cool and Cold Water Aquaculture Research
Title: Characterization of a Bacteriophage Specific for the Salmonid Pathogen Yersinia Ruckeri Author
Submitted to: Evergreen International Phage Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 7, 2005
Publication Date: August 7, 2005
Citation: Welch, T.J. 2005. Characterizaion of a bacteriophage specific for the salmonid pathogen yersinia ruckeri. Evergreen International Phage Meeting. the Evergreen State College, Olympia, WA. p. A-43. Technical Abstract: Infectious diseases are a major impediment to the U.S. Aquaculture industry. In addition, pathogens present in the effluent from aquaculture facilities pose a potential threat to populations of native aquatic organisms. While chemical antibiotics provide a powerful means for the control of pathogens their use causes serious environmental and human health concerns. Furthermore, antibiotic chemotherapeutics are of low specificity and cause disruptions in beneficial microflora, particularly in recirculating aquaculture systems which rely on microbiological removal of waste products. Bacteriophage have great potential as highly specific and self-replicating antimicrobials that offer a safe alternative to traditional chemical antibiotics. Here we present the isolation and partial characterization of a lytic bacteriophage (Phage NC10) with pathogenicity to Y. ruckeri, the causative agent of enteric redmouth disease (ERM). NC10 was isolated from sediments collected at a trout farm where outbreaks of ERM occur regularly. Electron microscopy of purified phage revealed viron particles with small (50 nm) polyhedral heads and no discernible appendages. Phage NC10 formed clear plaques of approximately 2 mm when propagated on solid media and exhibited a latent period of approximately 60 min and a burst size of approximately 100 PFU when grown in liquid culture. Spontaneous phage-resistant variants of Y. ruckeri fail to bind phage, are sensitive to rainbow trout serum, and are severely attenuated for virulence in rainbow trout. Purification and SDS-PAGE analysis of the lipopolysaccharides (LPS) produced by these variants revealed a defect in production of high-molecular-weight LPS, suggesting a role for O-polysaccharide in phage binding. Purified NC10 also displayed a polysaccharide depolymerase activity capable of degrading the Y. ruckeri O-polysaccharide polymer and rendering cells sensitive to rainbow trout sera. Current investigations are focused on assessing the effectiveness of phage YRNC10 for the treatment of Y. ruckeri infections and for the reduction of pathogen loads in aquaculture systems.