Genetic variation among F lavobacterium psychrophilum isolates from wild and farmed salmonids in N orway and C hile

Aims To aim of the study was to describe the genetic relationship between isolates of F lavobacterium psychrophilum with a main emphasis of samples from C hile and N orway. The isolates have been obtained from farmed salmonids in N orway and C hile, and from wild salmonids in N orway, but isolates from N orth A merica and E uropean countries are also included in the analysis. Methods and Results The study is based on phylogenetic analysis of 16 S r RNA and seven housekeeping genes ( HG ), gyr B , atp A , dna K , trp B , fum C , mur G and tuf , and the use of a multilocus sequence typing ( MLST ) system, based on nucleotide polymorphism in the HG , as an alternative to the phylogenies. The variation within the selected genes was limited, and the phylogenetic analysis gave little resolution between the isolates. The MLST gave a much better resolution resulting in 53 sequence types where the same sequences types could be found in C hile, N orth A merica and E uropean countries, and in different host species. Conclusions Multilocus sequence typing give a relatively good separation of different isolates of F l. psychrophilum and show that there are no distinct geographical or host‐specific isolates in the studied material from C hile, N orth A merica and E urope. Nor was it possible to separate between isolates from ulcers and systemic infections vs isolates from the surface of healthy salmonids. Significance and Impact of the Study This study shows a wide geographical distribution of F l. psychrophilum, indicating that the bacterium has a large potential for transmission over long distances, and between different salmonid hosts species. This knowledge will be important for future management of salmonids diseases connected to F l. psychrophilum .