title: Putative virulence genes in Moritella viscosa: activity during in vitro inoculation and in vivo infection.
abstract: Moritella viscosa is considered to be the main aetiological agent of winter ulcer disease, primarily affecting farmed salmonid fish in cold marine waters. Transcription profiles of twelve M. viscosa genes, potentially involved in the pathogenesis, were studied during the course of an in vitro cell culture infection assay. Transcription of the same genes was compared in vivo, in head kidney and ulcer tissues of Atlantic salmon challenged with M. viscosa. During the in vitro infection, three putative toxins: a putative repeats in toxin gene (rtxA), a putative cytotoxic necrotizing factor (cnf) and a putative hemolysin increased their transcription significantly with time and coincident with cell rounding. Furthermore, the majority of the genes were stimulated by presence of fish cells and showed higher activity when adhered to fish cells compared to their planktonic counterpart. In vivo gene transcription studies revealed an up-regulation of a putative lateral flagellin in ulcer compared to head kidney tissues in the same individual. A similar trend was seen for cnf and a gene encoding a putative protease, indicating a role for these factors in colonization and tissue damage.
authors.affiliation: Norwegian School of Veterinary Science, Department of Food Safety and Infection Biology, Pb 8146 Dep., 0033 Oslo, Norway.
authors.forename: Hege Smith
authors.initials: HS
authors.lastname: Tunsjø
authors.forename: Christer R
authors.initials: CR
authors.lastname: Wiik-Nielsen
authors.forename: Søren
authors.initials: S
authors.lastname: Grove
authors.forename: Eystein
authors.initials: E
authors.lastname: Skjerve
authors.forename: Henning
authors.initials: H
authors.lastname: Sørum
authors.forename: Trine M
authors.initials: TM
authors.lastname: L'abée-Lund
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000096:biosynthesis / Q000235:genetics; D018929:Cell Culture Techniques; D005393:Fish Diseases / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology*; D007668:Kidney / Q000382:microbiology; D034221:Moritella / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D016133:Polymerase Chain Reaction; D012329:RNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D048348:Reverse Transcription; D020317:Salmo salar; D014158:Transcription, Genetic; D014456:Ulcer / Q000382:microbiology / Q000662:veterinary*; D014774:Virulence
chemical_list: D001427:Bacterial Toxins; D012329:RNA, Bacterial