V. vulnificus gastroenteritis occurs most commonly after consumption of contaminated raw oysters and can lead to septicemia with a 50% fatality rate. This paper shows that V. vulnificus, among many other species of the genera Vibrionacea expresses sialic acid-like molecules. We found that Lineage I and Lineage II isolates, which are mostly clinical and environmental isolates respectively, encode lineage-specific alleles of the biosynthetic pathway for these sugars. Moreover, Lineage I isolates of mostly clinical origin have on average 40X higher density of expression of these molecules on their surface compared to Lineage II isolates of mostly environmental origin. A high density of sialic acid-like sugars on V. vulnificus may be significant during bloodstream infection by allowing the bacterium to evade innate immune responses.
DMB HPLC analysis of diverse V. vulnificus isolates was carried out, and NulO expression levels were normalized to an internal control monosaccharide (Kdo) that is a part of the conserved core portion of LPS. (A) Raw HPLC data from strains representing the major V. vulnificus lineages (I and II) and common nab allele types (CMCP6 and YJ016). (B) Relative NulO expression levels in lineage I and II strains. (C) V. vulnificus isolates with CM-like alleles of nab genes have significantly higher levels of NulOs than isolates with YJ-like alleles. Most of the “untypeable” isolates do, in fact, express detectable NulOs but at levels that are intermediate compared to those of isolates with YJ-like or CM-like alleles. (B and C) The Mann-Whitney test was used for statistical evaluation (*, P < 0.05; * *, P < 0.01; * * *, P < 0.0001). Note the log scales.