Reproducible methods for experimental infection with Flavobacterium psychrophilum in rainbow trout Oncorhynchus mykiss

[摘要] ABSTRACT: Experiments were done in order to achieve a reproducible method that can be used to infect rainbow trout Oncorhynchus mykiss with Flavobacterium psychrophilum, the causal agent of coldwater disease and rainbow trout fry syndrome.The main method investigated was intraperitoneal injection, and this method was tested using isolates with different elastin-degrading profiles and representing different serotypes. Injecting trout, average weight 1 g, with 10⁴ CFU(colony-forming units) per fish caused cumulative mortalities around 60 to 70%. The virulent strains belonged to certain serotypes and degraded elastin. The intraperitoneal injection challenge method could be used on larger fish, but the infection dosewas 10⁷ CFU per fish before mortalities occurred. Bath infection and bath infection in combination with formalin treatment (stress) seemed to be reproducible methods that could be used as alternatives to the intraperitoneal method, although themortalities among infected trout were lower. The results of investigated methods were influenced by parameters such as the challenge isolate, number of fish in the tank affecting the infection pressure, origin of fish and weight of fish.

[学科分类] 生物科学（综合）

[关键词] Flavobacterium psychrophilum;Experimental infection;Intraperitoneal challenge;Bath challenge;Stress + bath challenge;Cohabitation challenge;Rainbow trout