Probiotic bacteria and their bacteriocins to replace antibiotics in salmon aquaculture

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Salmon are farmed in >24 countries, with Canada being the 4th largest producer after Norway, Chile & Scotland according to the UN Food & Agriculture Organization. The 3 most common species are Atlantic salmon (Salmo salar), chinook salmon (Oncorhynchus tshawytscha) and coho salmon (Oncorhynchus kisutch). Canada is the largest North American producer of farmed Atlantic salmon (116,528 metric tons with an estimated value of US $728 million in 2011). In British Columbia the >6000 people employed in hatcheries, fish farms and supporting activities generated >$800 million. However, farmed salmon are susceptible to bacterial disease and parasitic sea lice (Lepeophtheirus salmonis and Caligus species). Health Canada has approved 4 antibiotics to combat bacterial infections in salmon (oxytetracycline hydrochloride, florfenicol, sulfadiazine + trimethoprim, and sulfadimethoxine + ormetoprim). About 2.5% of salmon feed is treated: this corresponds to 21,330 kilograms of antibiotic used in 2007. Emamectin benzoate (SLICE) is an antiparasitic widely used to treat sea lice. However, these substances can persist in the environment (e.g. sea bed sediment) as well as in fish tissue, and can lead to drug resistance that can be transmitted to human pathogens. Bacteriocins, non-toxic antimicrobial peptides from non-pathogenic bacteria that grow on food, as well as their producing bacteria (probiotics), are prime candidates for replacement of antibiotics used in salmon. This application requests funding to examine use of probiotic bacteria and their bacteriocins to treat bacterial and sea lice infections in farmed salmon. The project is a collaboration between research groups in chemical biology, food science and aquaculture. In particular, the project will examine use of Carnobacterium piscicola UAL307 (approved by Health Canada as a food additive) as well as other species of both Gram positive and Gram negative bacteria to eliminate salmon diseases. Some candidates include Renibacterium salmoninarum (bacterial kidney disease), Aeromonas salmonicida (furunculosis), Vibrio anguillarum (vibriosis) and Moritella viscosa (winter ulcer). The use of Paenibacillus and Bacillus species to eliminate sea lice will be investigated.