Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 4490
Title: Identification of a third msa gene in Renibacterium salmoninarum and the associated virulence phenotype
Author: L. D. Rhodes, A. M. Coady, R. K. Deinhard
Publication Year: 2004
Journal: Applied and Environmental Microbiology
Volume: 70
Issue: 11
Pages: 6488-6494
DOI: 10.1128/ AEM.70.11.6488-6494.2004
Keywords: bacterial kidney disease,Genetics

 Renibacterium salmoninarum, a gram-positive diplococcobacillus, causes bacterial kidney disease, a condition that can result in extensive morbidity and mortality among stocks of fish. An immunodominant extracellular protein, called major soluble antigen (MSA), is encoded by two identical genes, msa1 and msa2. We found evidence for a third msa gene, msa3, which appears to be a duplication of msa1. Unlike msa1 and msa2, msa3 is not present in all isolates of R. salmoninarum. The presence of the msa3 locus does not affect total MSA production in culture conditions. In a challenge study, isolates possessing the msa3 locus reduced median survival in juvenile chinook salmon (Oncorhynchus tshawytscha) by an average of 34% at doses of <105 cells per fish compared to isolates lacking the msa3 locus. In contrast, no difference in survival was observed at the highest dose, 106 cells per fish. The phenotype associated with the msa3 locus and its nonuniform distribution may contribute to observed differences in virulence among R. salmoninarum isolates.

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Theme: Recovery, Rebuilding and Sustainability of Marine and Anadromous Species
Foci: Maximize effectiveness and minimize impacts of artificial propagation in recovery, rebuilding and stock sustainability