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Research Project: Integrated Research to Improve On-Farm Animal Health in Salmonid Aquaculture

Location: Cool and Cold Water Aquaculture Research

Title: Biogeography of the fish pathogen Aeromonas salmonicida inferred by vapA genotyping

item GULLA, SNORRE - Norwegian Veterinary Institute
item BAYLISS, SION - University Of Bath
item BJÖRNSDÓTTIR, BRYNDÍS - Icelandic Food Research Institute (MATÍS OHF)
item DALSGAARD, INGER - Technical University Of Denmark
item HAENEN, OLGA - Wageningen University And Research Center
item JANSSON, EVA - Uppsala University
item MCCARTHY, UNA - Marine Scotland
item SCHOLZ, FELIX - Fish Vet Group (IRELAND)
item VERCAUTEREN, MAAIKE - Ghent University
item VERNER-JEFFREYS, DAVID - Centre For Environment, Fisheries And Aquaculture Science (CEFAS)
item Welch, Timothy - Tim
item WIKLUND, TOM - Abo Akademi University
item COLQUHOUN, DUNCAN - University Of Bergen

Submitted to: FEMS Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2019
Publication Date: 4/12/2019
Citation: Gulla, S., Bayliss, S., Björnsdóttir, B., Dalsgaard, I., Haenen, O., Jansson, E., Mccarthy, U., Scholz, F., Vercauteren, M., Verner-Jeffreys, D., Welch, T.J., Wiklund, T., Colquhoun, D.J. 2019. Biogeography of the fish pathogen Aeromonas salmonicida inferred by vapA genotyping. FEMS Microbiology Letters. 366(7).

Interpretive Summary: Aeromonas salmonicida is a bacterial pathogen that causes significant disease loss in nearly all species of cultivated fish. Recently a simple A. salmonicida typing scheme was introduced based on DNA sequence variation in the vapA gene. In this work, we perform a comprehensive survey of A. salmonicida strains collected over a 59-year period from 50 fish species in 26 countries to study the biogeography of A. salmonicida and the link between the vapA gene and fish host. The results showed a strong correlation between vapA-type and host independent of the geographic source of the bacterial strain, suggesting a biological basis for the observed host/strain relationship.

Technical Abstract: A recently described typing system based on sequence variation in the vapA gene, encoding the A-layer surface protein array, allows unambiguous subtyping of Aeromonas salmonicida. In the present study we compile A-layer typing results from a total of 675 A. salmonicida isolates, recovered over a 59-year period from 50 different fish species in 26 countries. Nine novel A-layer types (15 - 23) are identified, several of which display a strong predilection towards certain fish hosts. A-layer typing and whole genome phylogeny of a subset of isolates resulted in compatible tree topologies, indicating the utility of vapA as a phylogenetic as well as epizootiological marker in A. salmonicida. A Microreact project ( has been created, allowing public access to the vapA analyses and relevant metadata. The results generated provide valuable insights into the global population structure of A. salmonicida, particularly in relation to its observed host spectrum.