title: Differential susceptibility of salmonid fishes to furunculosis correlates with differential serum enhancement of Aeromonas salmonicida extracellular protease activity.
abstract: Rainbow trout, Atlantic salmon and brown trout, respectively, exhibit an increasing order of susceptibility to furunculosis. We investigated if this may be due to a differential sensitivity to exotoxins or ability to inhibit the exoprotease which is required by the bacterium to digest protein for growth. Differences were slight in susceptibility to exotoxins and serum inhibition of exoprotease at high exotoxin:serum ratios. However, at low ratios brown trout serum markedly enhanced protease activity, salmon serum had little effect and rainbow trout serum maintained 50% inhibition. This implies that during the early stages of infection the potential for growth of the bacterium would be highest in brown trout and lowest in rainbow trout. Determinations of growth rates in fresh serum support this hypothesis. The enhancement of exoprotease activity by serum of susceptible species may represent an important virulence mechanism.
authors.affiliation: Marine Laboratory, Aberdeen, Scotland.
authors.forename: A E
authors.initials: AE
authors.lastname: Ellis
authors.forename: K J
authors.initials: KJ
authors.lastname: Stapleton
mesh_terms: D000333:Aeromonas / Q000201:enzymology* / Q000254:growth & development / Q000472:pathogenicity; D000818:Animals; D004198:Disease Susceptibility; D020689:Exopeptidases; D005393:Fish Diseases / Q000276:immunology* / Q000382:microbiology; D005667:Furunculosis / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D010447:Peptide Hydrolases / Q000378:metabolism*; D011480:Protease Inhibitors; D012474:Salmon; D012487:Salmonidae; D014337:Trout; D014774:Virulence
chemical_list: D011480:Protease Inhibitors; D020689:Exopeptidases; D010447:Peptide Hydrolases