In vitro passages impact on virulence of Saprolegnia parasitica to Atlantic salmon, Salmo salar L. parr. Issue 9 (30th September 2013)

• Record Type: Journal Article
• Authors: Songe, M M; Thoen, E; Evensen, Ø; Skaar, I
• Is Part Of: Journal of fish diseases. Volume 37:Issue 9(2014:Sep.)
• Page Start: 825
• Page End: 834
• Publication Date: 2013-09-30
• Subjects: Fishes -- Diseases -- Periodicals; 639.3
• DOI: 10.1111/jfd.12175
• Languages: English
• ISSNs: 0140-7775

Abstract

<abstract abstract-type="main" id="jfd12175-abs-0001"> <title>Abstract</title> <p>The effect of serial <italic>in vitro</italic> subculturing on three pathogenic strains of <italic>Saprolegnia parasitica</italic> was investigated. The isolates were passed through Atlantic salmon, <italic>Salmo salar </italic>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 Atlantic salmon parr. Morphological characterization of growth patterns was performed to observe differences occurring due to serial <italic>in vitro</italic> subculturing. Two of the strains declined in virulence after 15 successive <italic>in vitro</italic> subcultures, whereas one did not. This study is the first to investigate attenuation of virulence in <italic>Saprolegnia</italic> and whether or not isolates of <italic>S. parasitica</italic> 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 <italic>in vitro</italic> subculturing on glucose–yeast extract.</p> </abstract>