title: Putative virulence factors of atypical Aeromonas salmonicida isolated from Arctic charr, Salvelinus alpinus (L.), and European grayling, Thymallus thymallus (L.).
abstract: Atypical Aeromonas salmonicida (AAS) causes generalized lethal infections in farmed Arctic charr, Salvelinus alpinus (L.), and European grayling, Thymallus thymallus (L.), and is thus a serious threat for culture of these fish species. Virulence factors were studied among isolates of AAS from Arctic charr (n = 20), European grayling (n = 19) and other fish species (n = 20), of which 48 were of Finnish and 11 of Swedish origin. All isolates produced an A-layer. Extracellular products (ECP) of the AAS isolates did not produce detectable gelatinase and caseinase activity in test assays. Analysis of the same ECP preparations with substrate sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed weak proteolytic activity, indicating the different sensitivity of the detection methods used. The ECP from AAS isolates showed low cytotoxic activity against cultured cells. However, the ECP did not induce mortality in challenged Arctic charr. The results suggest that toxic components, like ECP, secreted by the bacterium may not be the major virulence factor in AAS-infection in Arctic charr and European grayling, and hence the pathogenesis also differs from the pathogenesis of AAS-infection in Atlantic salmon, Salmo salar L.
authors.affiliation: Kuopio Regional Laboratory, National Veterinary and Food Research Institute, Kuopio, Finland. jmadetoj@abo.fi
authors.forename: J
authors.initials: J
authors.lastname: Madetoja
authors.forename: P
authors.initials: P
authors.lastname: Pylkkö
authors.forename: T
authors.initials: T
authors.lastname: Pohjanvirta
authors.forename: L
authors.initials: L
authors.lastname: Schildt
authors.forename: S
authors.initials: S
authors.lastname: Pelkonen
mesh_terms: D000333:Aeromonas / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D000818:Animals; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics; D001427:Bacterial Toxins / Q000032:analysis / Q000378:metabolism; D003603:Cytotoxins / Q000032:analysis / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel / Q000662:veterinary; D005387:Finland; D005393:Fish Diseases / Q000382:microbiology*; D018093:Gelatinases / Q000032:analysis / Q000378:metabolism; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000662:veterinary*; D006461:Hemolysis; D008074:Lipoproteins / Q000032:analysis / Q000235:genetics; D008666:Metalloendopeptidases / Q000032:analysis / Q000378:metabolism; D012487:Salmonidae / Q000382:microbiology*; D013548:Sweden; D014337:Trout / Q000382:microbiology*; D014774:Virulence; D037521:Virulence Factors / Q000032:analysis* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D003603:Cytotoxins; D008074:Lipoproteins; D037521:Virulence Factors; D018093:Gelatinases; D008666:Metalloendopeptidases; C030895:caseinase