Project Number: 1930-32000-002-00
Project Type: Appropriated

Start Date: Jan 11, 2005
End Date: Jan 10, 2010

Objective:
1. Characterize virulence determinants produced by the rainbow trout pathogens Yersinia ruckeri and Flavobacterium psychrophilum. 2. Identify rainbow trout genes and factors that are critical to expression of innate and acquired immunity against Y. ruckeri and F. psychrophilum. 2a. Molecular identification and sequencing of antibiotic resistance and virulence genes in bacterial pathogens of aquaculture species. 3. Identify water quality factors that influence host susceptibility and pathogen refuge within a recirculating system, and evaluate the use of bacteriophage as a targeted antibacterial strategy in recirculating and serial reuse aquaculture systems.

Approach:
Virulence determinants and antibiotic resistance plasmids of Yersinia ruckeri and Flavobacterium psychrophilum will be identified using molecular genetic approaches. Y. ruckeri virulence factors will be established by screening transposon-induced mutants for attenuation of virulence. For F. psychrophilum, we will completely sequence the genome and target potential virulence genes for mutation. These studies will generate candidates for vaccines and rapid diagnostic assays. Host factors involved in innate and acquired immunity will be identified by bioinformatics and gene expression analyses. The expression of trout immune genes will be measured in vaccinated and challenged fish by RT-PCR and immune gene microarrays. These studies will identify targets for diagnostic assays measuring protective immunity. The impact of organic constituents on host disease susceptibility and microbial growth will be assessed in recirculating aquaculture systems. Pathogen refuges within culture systems will be identified to aid targeted disinfection strategies. These multidisciplinary efforts will define the important parameters governing infectious disease in order to develop effective vaccines, novel biotherapeutics and strategies for maintaining healthier fish rearing conditions for the aquaculture industry.