Publications by authors named "Duncan J Colquhoun"

Thirteen bacterial isolates of were sequenced and assembled. The strains were isolated from four disease outbreaks in farmed marine fish in Norway. Eight isolates were from (lumpfish), and five were from (turbot).

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The present study was undertaken to address the recent spate of pasteurellosis outbreaks among sea-farmed Atlantic salmon () in Norway and Scotland, coinciding with sporadic disease episodes in lumpfish () used for delousing purposes in salmon farms. Genome assemblies from 86 bacterial isolates cultured from diseased salmon or lumpfish confirmed them all as members of the family, with phylogenetic reconstruction dividing them into two distinct branches sharing <88% average nucleotide identity. These branches therefore constitute two separate species, namely and the as-yet invalidly named "".

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Chlamydiae like Chlamydia trachomatis and Chlamydia psittaci are well-known human and animal pathogens. Yet, the chlamydiae are a much larger group of evolutionary ancient obligate intracellular bacteria that includes predominantly symbionts of protists and diverse animals. This makes them ideal model organisms to study evolutionary transitions from symbionts in microbial eukaryotes to pathogens of humans.

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While both virulent and putatively avirulent Yersinia ruckeri strains exist in aquaculture environments, the relationship between the distribution of virulence-associated factors and de facto pathogenicity in fish remains poorly understood. Pan-genome analysis of 18 complete genomes, representing established virulent and putatively avirulent lineages of Y. ruckeri, revealed the presence of a number of accessory genetic determinants.

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A Multi-Locus Variable number of tandem repeat Analysis (MLVA) genotyping scheme was developed for the epidemiological study of Moritella viscosa, which causes 'winter ulcer' predominantly in sea-reared Atlantic salmon (Salmo salar L.). The assay involves multiplex PCR amplification of six Variable Number of Tandem Repeat (VNTR) loci, followed by capillary electrophoresis and data interpretation.

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Tenacibaculum piscium, a gram-negative bacterium isolated from the skin ulcers of sea-farmed fish, has only been described in Norway. In the present study, we examined 16 Chilean Tenacibaculum isolates recovered from different organs in moribund and dead Atlantic salmon (Salmo salar), Rainbow trout (Oncorhynchus mykiss) and Coho salmon (Oncorhynchus kisutch) cultured at different fish farms between 2014 and 2018. The present study applied biochemical, phenotypic, fatty acid and whole-genome sequence-based analyses to confirm the taxonomic status of the Chilean isolates.

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Although a number of genetically diverse Yersinia ruckeri strains are present in Norwegian aquaculture environments, most if not all outbreaks of yersiniosis in Atlantic salmon in Norway are associated with a single specific genetic lineage of serotype O1, termed clonal complex 1. To investigate the presence and spread of virulent and putatively avirulent strains in Norwegian salmon farms, PCR assays specific for Y. ruckeri (species level) and Y.

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Draft genome sequences of 23 sp. strains that were isolated from Cyclopterus lumpus (lumpfish) were investigated to elucidate possible routes of transmission between Salmo salar (Atlantic salmon) and lumpfish.

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Non-motile strains of Yersinia ruckeri, known as Y. ruckeri biotype 2, now dominate amongst clinical isolates retrieved from rainbow trout internationally. Due to an acute increase in the number of yersiniosis cases in Norway in recent years, followed by introduction of widespread intraperitoneal vaccination against the disease, an investigation on the prevalence of Y.

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The bacterium Pseudomonas anguilliseptica has in recent years emerged as a serious threat to production of lumpfish in Norway. Little is known about the population structure of this bacterium despite its association with disease in a wide range of different fish species throughout the world. The phylogenetic relationships between 53 isolates, primarily derived from diseased lumpfish, but including a number of reference strains from diverse geographical origins and fish species, were reconstructed by Multi-Locus Sequence Analysis (MLSA) using nine housekeeping genes (rpoB, atpD, gyrB, rpoD, ileS, aroE, carA, glnS and recA).

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Pasteurellosis in farmed lumpsuckers, , has emerged as a serious disease in Norwegian aquaculture in recent years. Genomic characterization of the causative agent is essential in understanding the biology of the bacteria involved and in devising an efficient preventive strategy. The genomes of two clinical isolates were sequenced (≈2.

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Results of previous multilocus sequence and whole-genome-based analyses have suggested that a homogeneous group of isolates belonging to the genus , represented by strain TNO020 and associated with skin ulcer development in sea-farmed fish, represents an as-yet-undescribed species. Comparative whole-genome analysis performed in the present study clustered five isolates, including TNO020, in a distinct lineage within the genus . Phenotypic differences, high intra-cluster average nucleotide identity (ANI) values and low ANI values with other species support the proposal of a novel species, for which we propose the name sp.

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is a fastidious facultative intracellular bacterial pathogen that causes 'piscine francisellosis', a serious disease affecting both marine and fresh water farmed and wild fish worldwide. Currently two subspecies are recognized, i.e.

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This study examined the uptake, tissue distribution and elimination of the antibacterial agents oxolinic acid and flumequine in lumpfish ( L.) by use of LC-MS/MS following a single oral administration of 25 mg/kg fish given in feed. Lumpfish are increasingly used as cleaner fish for removal of sea lice on commercially farmed salmon.

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Various agents including Ca. Piscichlamydia salmonis, Ca. Branchiomonas cysticola, Desmozoon lepeophtherii, Paramoeba perurans and salmon gill poxvirus may be associated with complex gill disease in Atlantic salmon.

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Yersinia ruckeri is an important pathogen of farmed salmonids worldwide, but simple tools suitable for epizootiological investigations (infection tracing, etc.) of this bacterium have been lacking. A Multi-Locus Variable-number tandem-repeat Analysis (MLVA) assay was therefore developed as an easily accessible and unambiguous tool for high-resolution genotyping of recovered isolates.

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A recently described typing system based on sequence variation in the virulence array protein (vapA) gene, encoding the A-layer surface protein array, allows unambiguous subtyping of Aeromonas salmonicida. In the present study, we compile A-layer typing results from a total of 675 A. salmonicida isolates, recovered over a 59-year period from 50 different fish species in 26 countries.

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The present study was conducted to explore the occurrence of Flavobacteriaceae in wild Nile Tilapia Oreochromis niloticus (n = 108) collected from Lake Victoria and farmed Nile Tilapia (n = 187) collected from 12 ponds in the Morogoro region of Tanzania. The size of the ponds surveyed ranged from 130 to 150 m . Pond parameters and fish morphometric data were recorded during sampling.

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A multilocus variable-number tandem-repeat analysis (MLVA) assay was developed for epizootiological study of the internationally significant fish pathogen , which causes yersiniosis in salmonids. The assay involves amplification of 10 variable-number tandem-repeat (VNTR) loci in two five-plex PCRs, followed by capillary electrophoresis. A collection of 484 isolates, originating from various biological sources and collected from four continents over 7 decades, was analyzed.

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We performed RNA sequencing, identified components of the immune system and mapped early immune responses of lumpfish (Cyclopterus lumpus) leukocytes following in vitro exposure to the pathogenic bacterium Vibrio anguillarum O1. This is the first characterization of immune molecules in lumpfish at the gene level. In silico analyses revealed that genes encoding proteins involved in pathogen recognition, cell signaling and cytokines in mammals and teleosts are conserved in lumpfish.

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subsp. () is the causative agent of piscine francisellosis, an emerging infectious disease in Asia and Latin America. In this study two outbreaks of francisellosis were diagnosed in the UK on the basis of histopathology, electron microscopy, PCR, bacterial isolation and fulfillment of Koch's postulates.

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Secretion of extracellular vesicles (EVs) is a common feature of both eukaryotic and prokaryotic cells. Isolated EVs have been shown to contain different types of molecules, including proteins and nucleic acids, and are reported to be key players in intercellular communication. Little is known, however, of EV secretion in fish, or the effect of infection on EV release and content.

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So-called 'cleaner fish', including various wrasse (Labridae) species, have become increasingly popular in Norwegian salmon farming in recent years for biocontrol of the salmon louse Lepeophtheirus salmonis. Cleaner fish mortalities in salmon farms are, however, often high. Various bacterial agents are frequently associated with episodes of increased cleaner fish mortality, and Vibrio tapetis is regularly cultured from diseased wrasse.

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Skin ulcer development in sea-reared salmonids, commonly associated with Tenacibaculum spp., is a significant fish welfare- and economical problem in Norwegian aquaculture. A collection of 89 Tenacibaculum isolates was subjected to multilocus sequence analysis (MLSA).

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