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Photobacterium damselae subsp. damselae , an emerging pathogen in Danish rainbow trout, Oncorhynchus mykiss (Walbaum), mariculture
Author(s) -
Pedersen K,
Skall H F,
LassenNielsen A M,
Bjerrum L,
Olesen N J
Publication year - 2009
Publication title -
journal of fish diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 85
eISSN - 1365-2761
pISSN - 0140-7775
DOI - 10.1111/j.1365-2761.2009.01041.x
Subject(s) - rainbow trout , biology , haemolysis , virulence , microbiology and biotechnology , pathogen , photobacterium , bacteria , fishery , vibrio , fish <actinopterygii> , immunology , genetics , gene
A selection of 16 field isolates of Photobacterium damselae from marine rainbow trout farms in Denmark was subjected to phenotypic and genotypic characterization and pathogenicity to fish. All isolates belonged to the subspecies damselae , being positive for haemolysis, motility and urease. There were considerable differences in haemolytic properties, some isolates presenting a broad zone of haemolysis and others only a narrow zone. Pulsed‐field gel electrophoresis revealed a high diversity indicating that P. damselae subsp. damselae is an opportunistic, not clonal pathogen in Danish marine rainbow trout. Virulence of the strains to rainbow trout was highly variable with LD 50 values ranging from 3.9 × 10 3 to 1.5 × 10 8 cfu at 20 °C. The virulence was significantly higher at 20 °C than at 13 °C. The strains with the strongest haemolytic properties were the most virulent suggesting a strong involvement of haemolysin in the pathogenesis. The pathological changes were consistent with a bacterial septicaemia and the haemorrhages were more pronounced than for most other bacterial infections.