DAO 44:121-126 (2001)  -  doi:10.3354/dao044121

Characterization of attenuated Renibacterium salmoninarum strains and their use as live vaccines

J. G. Daly1,*, S. G. Griffiths2, A. K. Kew3, A. R. Moore3, G. Olivier3

1Division of Natural Sciences, Purchase College, State University of New York, Purchase, New York 10577, USA
2Research and Productivity Council, 921 College Hill Rd, Fredericton, New Brunswick E3B 6Z9, Canada
3Department of Fisheries and Oceans, Gulf Fisheries Centre, PO Box 5030, Moncton, New Brunswick E1C 9K1, Canada

ABSTRACT: Two nutritionally mutant strains of Renibacterium salmoninarum (Rs) were isolated that grew on tryticase soy agar (Rs TSA1) or brain heart infusion agar (Rs BHI1). These 2 strains could be continuously cultured on these media, whereas typical R. salmoninarum would only grow on KDM-2 agar. We determined no other phenotypic difference that could be used to distinguish them from wild-type R. salmoninarum. Both strains were found to be avirulent when 5 × 106 bacteria were intraperitoneally (IP) injected into Atlantic salmon. Rs TSA1, Rs BHI1, and Rs MT-239 (a R. salmoninarum strain previously shown to be attenuated) were tested as live vaccines in 2 separate trials. The best protection was seen with Rs TSA1. Vaccinated Atlantic salmon had relative percent survival (RPS) of 50 at 74 d post-challenge in Trial 1 and 76 at 60 d post-challenge in Trial 2. In both trials, 100% of the control salmon died from bacterial kidney disease (BKD) (within 40 d for Trial 1 and 50 d for Trial 2) after IP challenge with 5 × 106 live cells of the virulent isolate Rs Margaree.

KEY WORDS: Bacterial kidney disease · Renibacterium salmoninarum

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