Molecular and genetic characterization of cytochrome oxidase negative Aeromonas salmonicida isolated from coho salmon (Oncorhynchus kisutch)

Cytochrome oxidase variants of the bacterial fish pathogen, Aeromonas salmonicida, were characterized for genetic and molecular homology with cytochrome oxidase-positive isolates that typically induce furunculosis in salmonids. Protein and lipopolysaccharide moieties of the cytochrome oxidase-negative variants were similar to their typical counterparts, based on sodium-dodecyl-sulfate polyacrylamide gel electrophoresis. Pathogenicity of aberrant isolates to brook trout (Salvelinus fontinalis) was similar to typical cytochrome oxidase-positive isolates. Colorimetric deoxyribonucleic acid (DNA) hybridization in 96-well microplates yielded homology values greater than 82.5% for typical aberrant A. salmonicida isolates when photobiotinylated DNA for reference A. salmonicida 3.101 was used as a probe. The only variation of these isolates from typical A. salmonicida was a negative cytochrome oxidase reaction.