Taxonomic group: bacteria / Proteobacteria (Phylum: Proteobacteria)
Host organism: Salmo salar; Gadus morhua
Associated disease: hemorrhagic septicemia [ICD11: MA15.Y ]
 
NCBI PubMed ID: 30165113
Publication DOI: 10.1016/j.micpath.2018.08.058
Journal NLM ID: 8606191
Publisher: Academic Press
Correspondence: S.F. Norstebo <simen.foyn.norstebonmbu.no>
Institutions: Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine, Norwegian University of Life Sciences, PO Box 8146 Dep, 0033, Oslo, Norway, Department of Mechanical, Electronic and Chemical Engineering, Oslo and Akershus University College of Applied Sciences, PO Box 4 St. Olavs Plass, 0130, Oslo, Norway

Aliivibrio salmonicida is the causative agent of cold-water vibriosis, a hemorrhagic septicemia of salmonid fish. The bacterium has been shown to rapidly enter the fish bloodstream, and proliferation in blood is seen after a period of latency. Although the pathogenesis of the disease is largely unknown, shedding of high quantities of outer-membrane complex VS-P1, consisting of LPS and a protein moiety, has been suggested to act as decoy and contribute to immunomodulation. To investigate the role of LPS in the pathogenesis, we constructed O-antigen deficient mutants by knocking out the gene encoding O-antigen ligase waaL. As this gene exists in two copies in the Al. salmonicida genome, we constructed single and double in-frame deletion mutants to explore potential effects of copy number variation. Our results demonstrate that the LPS structure of Al. salmonicida is essential for virulence in Atlantic salmon. As the loss of O-antigen did not influence invasive properties of the bacterium, the role of LPS in virulence applies to later stages of the pathogenesis. One copy of waaL was sufficient for O-antigen ligation and virulence in experimental models. However, as a non-significant decrease in mortality was observed after immersion challenge with a waaL single mutant, it is tempting to suggest that multiple copies of the gene are beneficial to the bacterium at lower challenge doses. The loss of O-antigen was not found to affect serum survival in vitro, but quantification of bacteria in blood following immersion challenge suggested a role in in vivo survival. Furthermore, fish challenged with the waaL double mutant induced a more transient immune response than fish challenged with the wild type strain. Whether the reduction in virulence following the loss of waaL is caused by altered immunomodulative properties or impaired survival remains unclear. However, our data demonstrate that LPS is crucial for development of disease.

Lipopolysaccharide, Pathogenesis, O-antigen, Atlantic salmon, Aliivibrio salmonicida, Cold-water vibriosis

Structure type: oligomer
Location inside paper: p.323, fig.1A
The structure in this paper was incorrect:

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Compound class: core oligosaccharide
Contained glycoepitopes: IEDB_120354,IEDB_123890,IEDB_130650,IEDB_136105,IEDB_137777,IEDB_142488,IEDB_144998,IEDB_146664,IEDB_2189046,IEDB_2189047,IEDB_225177,IEDB_885823,IEDB_983931,SB_192
 
Methods: virulence assays, SDS-PAGE, DNA techniques, cytokine analysis, RT-PCR, RNA extraction
Comments, role: structure core region of LPS from ref. Edebrink et al., 1996 DOI:10.1016/0008-6215(96)00076-6; configuration of 8eLeg was revised to D-glycero-D-galacto in [Carbohydr Res 2001,331:233-237; doi 10.1016/S0008-6215(01)00041-6].
 
NCBI Taxonomy refs (TaxIDs): 40269
Show glycosyltransferases
 

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