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ARS Home » Northeast Area » Leetown, West Virginia » Cool and Cold Water Aquaculture Research » Research » Publications at this Location » Publication #305804
Title: Identification Of O-antigen biosynthetic genes specific to Serovar 01 Yersinia Ruckeri: Role in virulence and protective immunity

Author
item Welch, Timothy - Tim
item LAPATRA, SCOTT - Clear Springs Foods, Inc

Submitted to: International Aquatic Animal Health Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2014
Publication Date: 9/4/2014
Citation: Welch, T.J., Lapatra, S.E. 2014. Identification Of O-antigen biosynthetic genes specific to Serovar 01 Yersinia Ruckeri: Role in virulence and protective immunity [abstract]. International Aquatic Animal Health Symposium Proceedings. Paper No. 32F.

Interpretive Summary:

Technical Abstract: Yersinia ruckeri, the etiologic agent of enteric redmouth disease, causes a hemorrhagic septicemia that primarily affects farmed rainbow trout (Oncorhynchus mykiss, Walbaum). Y. ruckeri strains comprise several O-serotypes; however the majority of outbreaks are caused by serotype O1 isolates of this pathogen. Here, 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 known to be part of the O-polysaccharide repeat of O1 Y. ruckeri. Targeted mutation of one of the identified nonulosonic acid biosynthesis genes (nab2) resulted in loss of LPS synthesis and loss of cross reactivity with anti-O1 serotyping antisera. This loss of LPS biosynthesis was also shown to cause a dramatic reduction in serum resistance and a complete loss of virulence in a rainbow trout challenge model. Vaccination of rainbow trout with bacterin vaccines derived from the nab2 mutant and its wild type parent strain followed by IP injection challenge demonstrated that the LPS component of the bacterin vaccine is required to elicit a protective response. A similar protective response was observed when fish were vaccinated with purified LPS thus showing that LPS alone is sufficient to elicit a protective response. We also present a PCR-based serotyping method that can be used to identify serotype O1 Y. ruckeri strains.