DAO 105:203-210 (2013)  -  DOI: https://doi.org/10.3354/dao02609

Molecular epidemiology of Flavobacterium psychrophilum from Swiss fish farms

Nicole Strepparava1,*, Pierre Nicolas2, Thomas Wahli3, Helmut Segner3, Orlando Petrini1

1Cantonal Institute of Microbiology, Via Mirasole 22a, 6500 Bellinzona, Switzerland
2Institut National de la Recherche Agronomique (INRA), UR1077 Mathématique Informatique et Génome, 78350 Jouy-en-Josas, France
3Centre for Fish and Wildlife Health (FIWI), University of Bern, 3012 Bern, Switzerland

ABSTRACT: 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.


KEY WORDS: F. psychrophilum · BCWD · RTFS · Myxobacteria · Pathology · Clonal complex · Sequence complex · Allele type · MLST · Flavobacteriosis


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Cite this article as: Strepparava N, Nicolas P, Wahli T, Segner H, Petrini O (2013) Molecular epidemiology of Flavobacterium psychrophilum from Swiss fish farms. Dis Aquat Org 105:203-210. https://doi.org/10.3354/dao02609

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