title: Multilocus variable-number tandem-repeat genotyping of Renibacterium salmoninarum, a bacterium causing bacterial kidney disease in salmonid fish.
abstract: BACKGROUND
  Bacterial kidney disease (BKD), caused by Renibacterium salmoninarum, is a bacterial disease of fish, which is both geographically widespread and difficult to control. Previously, application of various molecular typing methods has failed to reliably discriminate between R. salmoninarum isolates originating from different host species and geographic areas. The current study aimed to utilize multilocus variable number tandem repeats (VNTR) to investigate inter-strain variation of R. salmoninarum to establish whether host-specific populations exist in Atlantic salmon and rainbow trout respectively. Such information would be valuable in risk assessment of transmission of R. salmoninarum in a multispecies aquaculture environment.
  
  
  RESULTS
  The present analysis utilizing sixteen VNTRs distinguished 17 different haplotypes amongst 41 R. salmoninarum isolates originating from Atlantic salmon and rainbow trout in Scotland, Norway and the US. The VNTR typing system revealed two well supported groups of R. salmoninarum haplotypes. The first group included R. salmoninarum isolates originating from both Atlantic salmon and rainbow trout circulating in Scottish and Norwegian aquaculture, in addition to the type strain ATCC33209T originating from Chinook salmon in North America. The second group comprised isolates found exclusively in Atlantic salmon, of mainly wild origin, including isolates NCIB1114 and NCIB1116 associated with the original Dee disease in Scotland.
  
  
  CONCLUSIONS
  The present study confirmed that VNTR analysis can be successfully applied to discriminate R. salmoninarum strains. There was no clear distinction between isolates originating from Atlantic salmon and rainbow trout as several haplotypes in group 1 clustered together R. salmoninarum isolates from both species. These findings indicate a potential exchange of pathogens between Atlantic salmon and rainbow trout in Scottish and Norwegian aquaculture during the last 20 years. In a scenario of expansion of rainbow trout farming into the marine environment, appropriate biosecurity measures to minimize disease occurrence are advised. The present results also suggest that R. salmoninarum isolates circulating in European aquaculture over the last 20 years are genetically distant to the wild strains originally causing BKD in the rivers Dee and Spey.
authors: Marine Scotland Science, Victoria Road, P,O, Box 101, Aberdeen AB11 9DB, UK. Iveta.Matejusova@scotland.gsi.gov.uk.
authors: Iveta
authors: I
authors: Matejusova
authors: Nicola
authors: N
authors: Bain
authors: Duncan J
authors: DJ
authors: Colquhoun
authors: Edward J
authors: EJ
authors: Feil
authors: Una
authors: U
authors: McCarthy
authors: Darryl
authors: D
authors: McLennan
authors: Michael
authors: M
authors: Snow
authors: David
authors: D
authors: Verner-Jeffreys
authors: I Stuart
authors: IS
authors: Wallace
authors: Sarah J
authors: SJ
authors: Weir
authors: Malcolm
authors: M
authors: Hall
mesh_terms: D000818:Animals; D017756:Aquaculture; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005393:Fish Diseases / Q000382:microbiology*; D014644:Genetic Variation; D005838:Genotype; D007674:Kidney Diseases / Q000382:microbiology / Q000662:veterinary*; D008835:Micrococcaceae / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D018598:Minisatellite Repeats; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D058889:Molecular Typing / Q000379:methods*; D009664:Norway; D012487:Salmonidae; D012606:Scotland; D017422:Sequence Analysis, DNA; D014481:United States
chemical_list: D004269:DNA, Bacterial