title: Phenotypic and genetic characterization of Piscirickettsia salmonis from Chilean and Canadian salmonids.
abstract: BACKGROUND
  The study presents the phenotypic and genetic characterization of selected P. salmonis isolates from Atlantic salmon and rainbow trout suffering from SRS (salmonid rickettsial septicemia) in Chile and in Canada. The phenotypic characterization of the P. salmonis isolates were based on growth on different agar media (including a newly developed medium), different growth temperatures, antibiotics susceptibility and biochemical tests.
  
  
  RESULTS
  This is the first study differentiating Chilean P. salmonis isolates into two separate genetic groups. Genotyping, based on 16S rRNA-ITS and concatenated housekeeping genes grouped the selected isolates into two clades, constituted by the Chilean strains, while the Canadian isolates form a branch in the phylogenetic tree. The latter consisted of two isolates that were different in both genetic and phenotypic characteristics. The phylogenies and the MLST do not reflect the origin of the isolates with respect to host species. The isolates included were heterogeneous in phenotypic tests.
  
  
  CONCLUSIONS
  The genotyping methods developed in this study provided a tool for separation of P. salmonis isolates into distinct clades. The SRS outbreaks in Chile are caused by minimum two different genetic groups of P. salmonis. This heterogeneity should be considered in future development of vaccines against this bacterium in Chile. Two different strains of P. salmonis, in regards to genetic and phenotypic characteristics, can occur in the same contemporary outbreak of SRS.
authors.affiliation: Fish Diseases Research Group, Department of Biology, University of Bergen, P.O. 7803, N-5020, Bergen, Norway.
authors.forename: Alexander
authors.initials: A
authors.lastname: Otterlei
authors.affiliation: Cermaq Group AS, Dronning Eufemias gate 16, P.O. Box 144 Sentrum, N-0102, Oslo, Norway.
authors.forename: Øyvind J
authors.initials: ØJ
authors.lastname: Brevik
authors.affiliation: Fish Diseases Research Group, Department of Biology, University of Bergen, P.O. 7803, N-5020, Bergen, Norway.
authors.forename: Daniel
authors.initials: D
authors.lastname: Jensen
authors.affiliation: Cermaq Group AS, Dronning Eufemias gate 16, P.O. Box 144 Sentrum, N-0102, Oslo, Norway.
authors.forename: Henrik
authors.initials: H
authors.lastname: Duesund
authors.affiliation: MSD Animal Health, Thormølensgt. 55, 5008, Bergen, Norway.
authors.forename: Ingunn
authors.initials: I
authors.lastname: Sommerset
authors.affiliation: MSD Animal Health, Thormølensgt. 55, 5008, Bergen, Norway.
authors.forename: Petter
authors.initials: P
authors.lastname: Frost
authors.affiliation: Cermaq Chile, Diego Portales 2000, piso 10, Puerto Montt, Chile.
authors.forename: Julio
authors.initials: J
authors.lastname: Mendoza
authors.affiliation: Cermaq Canada, 203 - 919 Island Highway, Campbell River, BC, V9W 2C2, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: McKenzie
authors.affiliation: Fish Diseases Research Group, Department of Biology, University of Bergen, P.O. 7803, N-5020, Bergen, Norway.
authors.forename: Are
authors.initials: A
authors.lastname: Nylund
authors.affiliation: Cermaq Group AS, Dronning Eufemias gate 16, P.O. Box 144 Sentrum, N-0102, Oslo, Norway. Patricia.Apablaza@cermaq.com.
authors.forename: Patricia
authors.initials: P
authors.lastname: Apablaza
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002170:Canada; D002677:Chile; D003470:Culture Media; D014644:Genetic Variation; D005838:Genotype; D008826:Microbial Sensitivity Tests; D017686:Oncorhynchus mykiss / Q000382:microbiology; D010802:Phylogeny; D053522:Piscirickettsia / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013696:Temperature
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D012336:RNA, Ribosomal, 16S
keywords: 16S rDNA-ITS; Genotyping; Housekeeping genes; MLST; P. salmonis; Phenotyping; Phylogeny