Rudenko, O., Angelucci, C., Kumanan, K., Delisle, E., Carson, J., Morrison, R. N., Hutson, K. S., and Barnes, A. C. (2025) Genomics and serotyping of Tenacibaculum maritimum outbreak isolates from Australia and New Zealand for guided vaccine development and stewardship. Aquaculture, 603. 742418.

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Abstract

Tenacibaculum maritimum is a ubiquitous marine bacterium with a remarkable ability to adhere to and form biofilm structures on abiotic and biotic surfaces including the skin and mucus of various marine fish species. Excessive colonisation of the fish epidermal surface is often associated with tenacibaculosis, a life-threatening skin infection that can progress to ulcerative lesions. Tenacibaculosis causes ongoing losses to finfish aquaculture worldwide, including the Atlantic salmon (Salmo salar) industry in Tasmania, Australia, and the King (Chinook) salmon (Oncorhynchus tshawytscha) industry in New Zealand, with no effective vaccine available. In this study we provide an evidence base for vaccine development by linking genomic analysis with antibody-based serotyping. We assembled and curated thirty-six complete genomes and thirty-six contig-level genomes of isolates from Tasmania and New Zealand, as well as three genomes of the overseas strains – Baxa lyl-1 (contig-level), NCIMB 2158 (complete), and NCIMB 2154^T type strain (complete). Core genome phylogenetic analysis indicated a high degree of geographic endemism and largely independent evolution of T. maritimum in Australia and New Zealand. Two main O-antigen gene cluster (O-AGC) types were identified in each location: type 3–2 was predominant in Tasmania, type 3–0 was predominant in New Zealand, while type 2–1 was the second most abundant type in both Tasmania and New Zealand. O-AGC type 3–2 appears to be endemic to Oceania, and one of the distinct phylogenetic lineages harbouring this O-antigen type (clade C1) appears to be endemic to Tasmania. Somewhat surprisingly, O-AGC types were highly conserved within phylogenetic clades and/or sub-clades. In the case of Tasmania, there was a partial concordance between O-AGC typing and antibody-based serotyping. Importantly, variation in serotyping results within O-AGC type 3–2 isolates was clearly linked to phylogenetic clustering. In the case of New Zealand, antibody serotyping did not distinguish between O-AGC types. We hypothesise this may be due to high amount of a colanic acid (CA) capsule or similar exopolysaccharide and its binding to the LPS core. Stress-inducible CA capsule is critical for biofilm formation in other bacterial species, and here we report for the first time the putative CA exopolysaccharide cluster (K-AGC) in T. maritimum which may aid more rigorous typing and vaccine development.

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