title: Co-infection of Atlantic salmon (Salmo salar), by Moritella viscosa and Aliivibrio wodanis, development of disease and host colonization.
abstract: Two species of bacteria are repeatedly isolated from farmed fish with winter-ulcer disease. Moritella viscosa is the aetiological agent of the disease; the significance of Aliivibrio wodanis is uncertain but has not been related to the primary pathogenesis. A cell culture infection model showed that A. wodanis adhered to, but did not invade the fish cells. Exposure to culture supernatant of A. wodanis caused the fish cells to vacoulate, retract, round up and detach from the surface, and rearrange the actin filaments of the cytoskeleton. These observations suggest that the bacterium secretes toxins into the extracellular environment. Any pathologic effect of A. wodanis and the effect of co-culturing with M. viscosa was studied in Atlantic salmon (Salmo salar) bath challenged with; only M. viscosa or only A. wodanis or both bacteria together. Both M. viscosa and A. wodanis were re-isolated from external surfaces and internal organs from live and deceased co-infected fish. It is further hypothesized that A. wodanis colonization might influence the progression of a M. viscosa infection. This is to our knowledge the first study that reproduces field observations where both bacteria infect Atlantic salmon.
authors.affiliation: Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., 0033 Oslo, Norway. Electronic address: christian.karlsen@nmbu.no.
authors.forename: Christian
authors.initials: C
authors.lastname: Karlsen
authors.affiliation: Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., 0033 Oslo, Norway.
authors.forename: Christin
authors.initials: C
authors.lastname: Vanberg
authors.affiliation: Nofima AS, P.O. Box 6122, 9291 Tromsø, Norway.
authors.forename: Helene
authors.initials: H
authors.lastname: Mikkelsen
authors.affiliation: Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, P.O. Box 8146 Dep., 0033 Oslo, Norway.
authors.forename: Henning
authors.initials: H
authors.lastname: Sørum
mesh_terms: D000199:Actins / Q000378:metabolism; D059706:Aliivibrio / Q000502:physiology*; D059707:Aliivibrio Infections / Q000401:mortality / Q000473:pathology; D000818:Animals; D002460:Cell Line; D002477:Cells / Q000187:drug effects; D060085:Coinfection; D017077:Culture Media, Conditioned / Q000633:toxicity; D005393:Fish Diseases / Q000382:microbiology* / Q000473:pathology*; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000401:mortality / Q000473:pathology*; D034221:Moritella / Q000502:physiology*; D020317:Salmo salar; D016019:Survival Analysis
chemical_list: D000199:Actins; D017077:Culture Media, Conditioned
keywords: Aliivibrio wodanis; Co-infection; Cytotoxicity; Moritella viscosa; Winter-ulcer