title: Mycobacterium salmoniphilum infection in farmed Atlantic salmon, Salmo salar L.
abstract: Multiple greyish-white visceral nodules containing abundant rapidly growing and acid-fast bacteria, subsequently identified as Mycobacterium salmoniphilum, were detected in moribund and newly dead market-sized fish during a period of increased mortality in an Atlantic salmon, Salmo salar, farm in western Norway. Isolates cultured from diseased fish were phenotypically consistent with Mycobacterium sp. previously isolated from Atlantic salmon [MT 1890 (= NCIMB13533), MT1892, MT1900 and MT1901] in the Shetland Isles, Scotland. Partial sequences of 16S rDNA, ribosomal RNA internal transcribed spacer (ITS1), 65-kDa heat-shock protein (Hsp65) and β subunit of RNA polymerase (rpoB) revealed 97-99% similarity with M. salmoniphilum type strain ATCC 13758(T) . The source of infection was not confirmed. Koch's postulates were fulfilled following experimental challenge of Atlantic salmon with field isolate NVI6598 (FJ616988). Mortality was recorded in experimentally infected fish; however, the infection remained subclinical in the majority of affected fish over the 131-day challenge period.
authors.affiliation: National Veterinary Institute, Oslo, Norway. adam.zerihun@vetinst.no
authors.forename: M A
authors.initials: MA
authors.lastname: Zerihun
authors.forename: H
authors.initials: H
authors.lastname: Nilsen
authors.forename: S
authors.initials: S
authors.lastname: Hodneland
authors.forename: D J
authors.initials: DJ
authors.lastname: Colquhoun
mesh_terms: D000818:Animals; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D005393:Fish Diseases / Q000382:microbiology* / Q000401:mortality / Q000473:pathology*; D005398:Fisheries; D005798:Genes, Bacterial / Q000235:genetics; D008969:Molecular Sequence Data; D009161:Mycobacterium / Q000145:classification / Q000235:genetics*; D009164:Mycobacterium Infections / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D020317:Salmo salar; D016415:Sequence Alignment
chemical_list: D021903:DNA, Ribosomal Spacer; D012336:RNA, Ribosomal, 16S