title: Prevalence, geographic distribution and phenotypic differences of Piscirickettsia salmonis EM-90-like isolates.
abstract: Early reports accounted for two main genotypes of Piscirickettsia salmonis, a fish pathogen and causative agent of piscirickettsiosis, placing the single isolate EM-90 apart from the prototypic LF-89 and related isolates. In this study, we provide evidence that, contrary to what has been supposed, the EM-90-like isolates are highly prevalent and disseminated across Chilean marine farms. Molecular analysis of 507 P. salmonis field isolates derived from main rearing areas, diverse hosts and collected over 6 years, revealed that nearly 50% of the entire collection were indeed typed as EM-90-like. Interestingly, these isolates showed a marked host preference, being recovered exclusively from Atlantic salmon (Salmo salar) samples. Although both strains produce undistinguishable pathological outcomes, differences regarding growth kinetics and susceptibility to the antibiotics and bactericidal action of serum could be identified. In sum, our results allow to conclude that the EM-90-like isolates represent an epidemiologically relevant group in the current situation of piscirickettsiosis. Based on the consistency between genotype and phenotype exhibited by this strain, we point out the need for genotypic studies that may be as important for the Chilean salmon industry as the continuous surveillance of antimicrobial susceptibility patterns.
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: J
authors.initials: J
authors.lastname: Saavedra
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: N
authors.initials: N
authors.lastname: Hernandez
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: A
authors.initials: A
authors.lastname: Osses
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: A
authors.initials: A
authors.lastname: Castillo
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: A
authors.initials: A
authors.lastname: Cancino
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: H
authors.initials: H
authors.lastname: Grothusen
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: E
authors.initials: E
authors.lastname: Navas
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: P
authors.initials: P
authors.lastname: Henriquez
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: H
authors.initials: H
authors.lastname: Bohle
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: F
authors.initials: F
authors.lastname: Bustamante
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: P
authors.initials: P
authors.lastname: Bustos
authors.affiliation: Laboratorio de Diagnóstico y Biotecnología, ADL Diagnostic Chile Ltda, Puerto Montt, Chile.
authors.forename: M
authors.initials: M
authors.lastname: Mancilla
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002677:Chile / Q000453:epidemiology; D024881:Drug Resistance, Bacterial; D005393:Fish Diseases / Q000453:epidemiology* / Q000382:microbiology; D005838:Genotype; D017683:Oncorhynchus; D053522:Piscirickettsia / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D044225:Piscirickettsiaceae Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D015995:Prevalence; D020317:Salmo salar; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents
keywords: 
  Piscirickettsia salmonis
  ; EM-90; antibiotic resistance; epidemiology; genotype