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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED APPROACHES FOR IMPROVING AQUATIC ANIMAL HEALTH IN COOL AND COLD WATER AQUACULTURE

Location: Cool and Cold Water Aquaculture Research

Title: Identification of O-Antigen biosynthetic genes specific to Serovar 01 Yersinia Ruckeri: Role in virulence and protective immunity

Authors
item Welch, Timothy
item Lapatra, Scott -

Submitted to: Annual Eastern Fish Health Workshop
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2014
Publication Date: April 28, 2014
Citation: Welch, T.J., Lapatra, S. 2014. Identification of O-Antigen biosynthetic genes specific to Serovar 01 Yersinia Ruckeri: Role in virulence and protective immunity [abstract]. Annual Eastern Fish Health Workshop. A65.

Technical Abstract: Yersinia ruckeri is the etiologic agent of enteric redmouth disease, a hemorrhagic septicemia that primarily affects farmed rainbow trout (Oncorhynchus mykiss, Walbaum). Y. ruckeri strains comprise several O-serotypes; however the vast majority of outbreaks are caused by serotype O1 isolates of this pathogen. In this study we used genome sequencing to identify a large cluster of O-antigen biosynthetic genes specific to serotype O1 Y. ruckeri strains. This cluster consisted of genes encoding proteins predicted to function in O-antigen and LPS biosynthesis including proteins predicted to function in the biosynthesis of Legionamic acid, a nonulosonic acid know to be part of the O-polysaccharide repeat of O1 Y. ruckeri. Mutation of one of the identified nonulosonic acid biosynthesis genes (nab2) resulted in loss of LPS synthesis and loss of both serum resistance and virulence in a rainbow trout challenge model. Vaccination with bacterin vaccines derived from the nab2 mutant and its wild type parent strain was done in rainbow trout and susceptibility to Y. ruckeri was evaluated post-vaccination. Significant protection against challenge with Y. ruckeri was only observed in fish vaccinated with the wild type strain indicating that the presence of LPS is required to mount a protective response against Y. ruckeri challenge.

Last Modified: 9/22/2014
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