Molecular epidemiology of Flavobacterium psychrophilum from Swiss fish farms

• Published in: Diseases of Aquatic Organisms
• Main Authors: Strepparava, Nicole, Nicolas, Pierre, Wahli, Thomas, Segner, Helmut, Petrini, Orlando
• Other Authors: Cantonal Institute of Microbiology, Unité Mathématique Informatique et Génome (MIG), Institut National de la Recherche Agronomique (INRA), University of Bern, EU EMIDA ERA-NET project PATHOFISH ANR 2010-EMID-006-01, Swiss Federal Veterinary Office (FVO)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: F. psychrophilum; BCWD; RTFS; Myxobacteria; Pathology; Clonal complex; Sequence complex; Allele type; BACTERIAL COLDWATER DISEASE; AYU PLECOGLOSSUS-ALTIVELIS; CYTOPHAGA-PSYCHROPHILA; SEQUENCE; DIVERSITY; EBURST; MLST; Flavobacteriosis; SALMON SALMO-SALAR; POPULATION-STRUCTURE; [MATH]Mathematics [math]; [INFO]Computer Science [cs]; [SDV]Life Sciences [q-bio]; Salmo salar
• Online Access: https://hal.inrae.fr/hal-02651608; https://doi.org/10.3354/dao02609

International audience Bacterial cold water disease (BCWD) and rainbow trout fry syndrome (RTFS) caused by Flavobacterium psychrophilum are 2 of the major diseases causing high fish mortality in salmonid fish farms. The molecular epidemiology of F. psychrophilum is still largely unknown. Multilocus sequence typing (MLST) has been previously used for this pathogen and underscored a correlation between clonal complexes and host fish species. Here we used MLST to study the relationships among 112 F. psychrophilum isolates from rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta fario and S. t. lacustris in Swiss fish farms between 1993 and 2012. The isolates belonged to 27 different sequence types (STs). Most of the Swiss outbreaks were associated with strains belonging to clonal complexes CC-ST2 and CC-ST90, found in both rainbow trout and brown trout and represented by several STs. Eight ST singletons could not be connected to any known clonal complex. Already reported from other parts of Europe and North America, CC-ST2 was the most frequent clonal complex observed, and it caused the majority of outbreaks in Switzerland, with CC-ST90 being the second most important type. In the tightly interconnected Swiss fish farms, no association between clonal complex and host fish was detected, but a temporal evolution of the frequency of some STs was observed. The occurrence of sporadic STs suggests high F. psychrophilum diversity and may reflect the presence of different sequence types in the environment.