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In vitro passages impact on virulence of S aprolegnia parasitica to A tlantic salmon, S almo salar L . parr
Author(s) -
Songe M M,
Thoen E,
Evensen Ø,
Skaar I
Publication year - 2014
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/jfd.12175
Subject(s) - subculture (biology) , virulence , salmo , biology , microbiology and biotechnology , saprolegnia , serial passage , in vitro , spore , fish <actinopterygii> , strain (injury) , gene , fishery , genetics , anatomy
The effect of serial in vitro subculturing on three pathogenic strains of S aprolegnia parasitica was investigated. The isolates were passed through A tlantic salmon, S almo salar L . parr, and then re‐isolated as single spore colonies. All strains caused infection. The isolate obtained from diseased fish served as a virulent reference culture and was designated ‘ AP ’ (‘activated through passage’). Successive subculturing was made by obtaining an inoculum from AP to produce the 2nd subculture and then passaged to the 3rd subculture (from the 2nd), until the 15th passage was obtained. Spores used to produce storage cultures were collected at passages 5, 10 and 15. The different passages of each strain were used to artificially infect A tlantic salmon parr. Morphological characterization of growth patterns was performed to observe differences occurring due to serial in vitro subculturing. Two of the strains declined in virulence after 15 successive in vitro subcultures, whereas one did not. This study is the first to investigate attenuation of virulence in S aprolegnia and whether or not isolates of S . parasitica should be passed through the fish host prior to challenge experiments. It reveals that some strains degenerate more rapidly than others when subjected to successive in vitro subculturing on glucose–yeast extract.