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Virulence of Aeromonas salmonicida : Lack of Relationship with Phenotypic Characteristics
Author(s) -
Olivier G.
Publication year - 1990
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1577/1548-8667(1990)002<0119:voslor>2.3.co;2
Subject(s) - virulence , aeromonas salmonicida , biology , microbiology and biotechnology , salvelinus , aeromonas , trout , aerolysin , bacteria , virology , fish <actinopterygii> , gene , fishery , genetics , biochemistry
The pathogenicity of 28 Aeromonas salmonicida isolates was investigated by intraperitoneal injection into juvenile brook trout Salvelinus fontinalis. Ten isolates were found to be virulent, killing 100% or 87–100% of experimental animals following injections of 1 × 10 6 or 1 × 10 3 colony‐forming units (CFU)/fish, respectively. All virulent isolates possessed an A layer, autoaggregated in liquid culture, and were positive on Coomassie brilliant blue and Congo red (CR) media. Nine isolates, which were negative for all of the above characteristics, were avirulent in fish and caused no mortality following an injection of 1 × 10 6 CFU/fish. The last group of nine isolates was also avirulent (no mortality after an injection of 1 × 10 6 CFU/fish) and are referred to as A + avirulent strains because they possess the same in vitro characteristics as the virulent strains described above. For all isolates, the following cell‐surface‐related properties were then investigated: Cell‐surface hydrophobicity, presence of a yeast agglutinin, resistance to A. salmonicida bacteriophage 37, and resistance to the bactericidal activity of normal brook trout serum. The ability of isolates to produce extracellular protease was also determined. Our results indicate that all of the in vitro tests mentioned previously cannot predict the virulence of A. salmonicida isolates and that the only valid method to assess virulence is in vivo challenge.