title: Microevolution of Renibacterium salmoninarum: evidence for intercontinental dissemination associated with fish movements.
abstract: Renibacterium salmoninarum is the causative agent of bacterial kidney disease, a major pathogen of salmonid fish species worldwide. Very low levels of intra-species genetic diversity have hampered efforts to understand the transmission dynamics and recent evolutionary history of this Gram-positive bacterium. We exploited recent advances in the next-generation sequencing technology to generate genome-wide single-nucleotide polymorphism (SNP) data from 68 diverse R. salmoninarum isolates representing broad geographical and temporal ranges and different host species. Phylogenetic analysis robustly delineated two lineages (lineage 1 and lineage 2); futhermore, dating analysis estimated that the time to the most recent ancestor of all the isolates is 1239 years ago (95% credible interval (CI) 444-2720 years ago). Our data reveal the intercontinental spread of lineage 1 over the last century, concurrent with anthropogenic movement of live fish, feed and ova for aquaculture purposes and stocking of recreational fisheries, whilst lineage 2 appears to have been endemic in wild Eastern Atlantic salmonid stocks before commercial activity. The high resolution of the SNP-based analyses allowed us to separate closely related isolates linked to neighboring fish farms, indicating that they formed part of single outbreaks. We were able to demonstrate that the main lineage 1 subgroup of R. salmoninarum isolated from Norway and the UK likely represent an introduction to these areas ~40 years ago. This study demonstrates the promise of this technology for analysis of micro and medium scale evolutionary relationships in veterinary and environmental microorganisms, as well as human pathogens.
authors.affiliation: EpiCentre, Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway.
authors.forename: Ola
authors.initials: O
authors.lastname: Brynildsrud
authors.affiliation: Department of Biology and Biochemistry, University of Bath, Bath, UK.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Feil
authors.affiliation: EpiCentre, Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway.
authors.forename: Jon
authors.initials: J
authors.lastname: Bohlin
authors.affiliation: Department of Biology and Biochemistry, University of Bath, Bath, UK.
authors.forename: Santiago
authors.initials: S
authors.lastname: Castillo-Ramirez
authors.affiliation: Section for Bacteriology, Department of Laboratory Services, Norwegian Veterinary Institute, Oslo, Norway.
authors.forename: Duncan
authors.initials: D
authors.lastname: Colquhoun
authors.affiliation: Marine Scotland Science, Aberdeen, Scotland, UK.
authors.forename: Una
authors.initials: U
authors.lastname: McCarthy
authors.affiliation: Marine Scotland Science, Aberdeen, Scotland, UK.
authors.forename: Iveta M
authors.initials: IM
authors.lastname: Matejusova
authors.affiliation: NOAA, Northwest Fisheries Science Center, Seattle, WA, USA.
authors.forename: Linda D
authors.initials: LD
authors.lastname: Rhodes
authors.affiliation: USDA, National Centre for Cool and Coldwater Aquaculture, Leetown, WV, USA.
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Wiens
authors.affiliation: Cefas Weymouth Laboratory, The Nothe, Weymouth, UK.
authors.forename: David W
authors.initials: DW
authors.lastname: Verner-Jeffreys
mesh_terms: D000193:Actinomycetales Infections / Q000382:microbiology*; D000818:Animals; D004269:DNA, Bacterial / Q000235:genetics; D005393:Fish Diseases / Q000382:microbiology*; D008835:Micrococcaceae / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D009664:Norway; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011157:Population Dynamics; D012487:Salmonidae / Q000382:microbiology* / Q000502:physiology*; D013995:Time
chemical_list: D004269:DNA, Bacterial