Comparative Genomic Analysis of Virulent Vibrio (Listonella) anguillarum Serotypes Revealed Genetic Diversity and Genomic Signatures in the O-Antigen Biosynthesis Gene Cluster

Proteomics analysis of extracellular vesicles during Vibrio anguillarum infection in lumpfish (Cyclopterus lumpus)

Lumpfish (Cyclopterus lumpus) is a native fish of the North Atlantic Ocean used as sea lice biocontrol in Atlantic salmon farms. Lumpfish also has been used as model for marine infectious diseases and immunity. Lumpfish is susceptible to Vibrio anguillarum infection, and upon infection, lumpfish immunity is activated to preclude the disease progression. Extracellular vesicles (EVs) play an important role in early immune cellular communication. Lumpfish EVs and their potential role in immunity have not been explored. Herein, EVs where isolated from serum of naïve lumpfish and from lumpfish infected with V. anguillarum at 5 and 10 days post infection (dpi). EVs characteristics were studied by electron microscopy and nanoparticle tracking, and protein cargo was analysed by Western blot and proteomic analysis. The isolated EVs showed a spherical shape ranging from ∼30 nm to 300 nm in diameter, but at 5 dpi the size variation was higher. A total of 395 proteins were identified. Upregulated proteins were linked to complement pathway/innate immunity, heme/iron binding, defense response to bacterium, apoptotic signaling pathway, and actin binding. Downregulated proteins were associated with ribonucleoprotein/ribosomal protein, transport and translation elongation factor activity, acute phase, protein phosphorylation and apoptotic process. Upon infection V. anguillarum infection, lumpfish EVs cargo was modified, from transporting metabolic proteins to proteins related to immunity. Characterization of peripheral lumpfish EVs protein profile during V. anguillarum infection provided with potential biomarkers repertoire that could be utilised in the development of novel tools to diagnose and control of V. anguillarum infection in finfish aquaculture.

Influence of Vibrio anguillarum culture conditions on the efficacy of bacterin-based vaccines in lumpfish (Cyclopterus lumpus)

Lumpfish (Cyclopterus lumpus) is used as cleaner fish to control sea lice infestations in Atlantic salmon (Salmo salar) farms across the North Atlantic. Vibrio anguillarum, the causative agent of vibriosis, is a recurrent bacterial pathogen affecting lumpfish. Bacterin-based vaccines are frequently used to control vibriosis in finfish, but their efficacy is not always consistent. Culture conditions significantly influence synthesis of bacterial outer membrane and secreted proteins, which are critical antigens, and thus impact the immunogenicity of bacterin-based vaccines. In this study, we assessed the effect of V. anguillarum culture conditions on vaccine efficacy in lumpfish. V. anguillarum was cultured under iron-limited at 15 °C, and iron-rich or iron-limited conditions at 28 °C with 2 % NaCl, and these cultures were used to prepare bacterins. A commercial vaccine was used as positive control, while PBS and PBS adjuvant were negative controls. Lumpfish were intraperitoneally immunized and challenged 12 weeks post-immunization with 10-100 times the LD50 dose of V. anguillarum. Bacterins prepared from V. anguillarum grown under iron-limited conditions at 28 °C with 2 % NaCl and mixed with adjuvant conferred the highest protection compared to other preparations and commercial vaccines. In contrast, bacterins derived from V. anguillarum cultured under iron-limited conditions at 15 °C conferred the lowest protection. Reverse vaccinology and transcriptomic analyses of V. anguillarum grown under optimal immunogenic conditions revealed 323 upregulated genes, of which 211 were high-antigenicity proteins suitable for subunit vaccines. This study provides critical knowledge for effective vaccine formulation against V. anguillarum and identifies potential antigens for subunit vaccine development.

Revealing antimicrobial resistance profile and associated factors of Vibrio vulnificus isolated from clinical, environmental, and seafood samples across asia: A systematic review and meta-analysis

The escalating antimicrobial resistance (AMR) in highly virulent Vibrio vulnificus poses a significant public health concern in Asia. Profiling the antibiogram of this pathogen is crucial for revealing its complex AMR patterns and guiding the selection of appropriate medications. Although previous studies have provided valuable insights regarding V. vulnificus AMR, they are constrained by limited sample diversity, inconsistent methodologies, and insufficient regional data. Moreover, no systematic attempt has been made to synthesize V. vulnificus AMR data across various sources and regions in Asia. A systematic review and meta-analysis are thus conducted in this study to assess the current AMR status of V. vulnificus isolated from clinical, environmental, and seafood samples. By synthesizing data from 32 articles across 13 Asian countries, a broader antibiogram has been provided, covering 13 major antimicrobial groups against V. vulnificus. Subgroup and regression analyses were also performed using study-level and country-specific covariates to explore the associated risk factors. The findings revealed low AMR rates for tetracyclines (4.89 %), quinolones (1.85 %), nitrofurans (0.86 %), and phenicols (0.61 %), highlighting their potential as primary treatment options. Conversely, high AMR rates were detected for lincosamides (80.32 %), polypeptides (64.42 %), and glycopeptides (56.14 %), necessitating careful consideration for their clinical use. For study-level covariates, subgroup and meta-regression analyses revealed that variations in the type of antimicrobial (R 2  = 26.5 %, p < 0.0001), country (R 2  = 18.33 %, p < 0.0001), and pathogen source (R 2  = 10.46 %, p = 0.0007) significantly contributed to between-study heterogeneity in the detected AMR rates across studies. Moreover, the analyses of country-specific covariates indicated that antimicrobial consumption (AMC) in healthcare systems (R 2  = 29.3, p = 0.06) and the country's gross domestic product (GDP) (R 2  = 28.59, p = 0.06) affected the variations in AMR rates across countries to some extent. Consideration of study-level and country-specific covariates is thus recommended for future research to effectively mitigate the threat of V. vulnificus AMR across Asia and reduce its pervasive impact on public health.

Systematic analysis of ocular features and responses of cultured spotted wolffish (Anarhichas minor)

A better understanding of unique anatomical and functional features of the visual systems of teleost fish could provide key knowledge on how these systems influence the health and survival of these animals in both wild and culture environments. We took a systematic approach to assess some of the visual systems of spotted wolffish (Anarhichas minor), a species of increasing importance in North Atlantic aquaculture initiatives. The lumpfish (Cyclopterus lumpus) was included in these studies in a comparative manner to provide reference. Histology, light and electron microscopy were used to study the spatial distribution and occurrence of cone photoreceptor cells and the nature of the retinal tissues, while immunohistochemistry was used to explore the expression patterns of two photoreceptor markers, XAP-1 and XAP-2, in both species. A marine bacterial infection paradigm in lumpfish was used to assess how host-pathogen responses might impact the expression of these photoreceptor markers in these animals. We define a basic photoreceptor mosaic and present an ultrastructural to macroscopic geographical configuration of the retinal pigment tissues in both animals. Photoreceptor markers XAP-1 and XAP-2 have novel distribution patterns in spotted wolffish and lumpfish retinas, and exogenous pathogenic influences can affect the normal expression pattern of XAP-1 in lumpfish. Live tank-side ophthalmoscopy and spectral domain optical coherence tomography (SD-OCT) revealed that normal cultured spotted wolffish display novel variations in the shape of the retinal tissue. These two complementary imaging findings suggest that spotted wolffish harbour unique ocular features not yet described in marine teleosts and that visual function might involve specific retinal tissue shape dynamics in these animals. Finally, extensive endogenous biofluorescence is present in the retinal tissues of both animals, which raises questions about how these animals might use retinal tissue in novel ways for visual perception and/or communication. This work advances fundamental knowledge on the visual systems of two economically important but now threatened North Atlantic teleosts and provides a basic foundation for further research on the visual systems of these animals in health versus disease settings. This work could also be useful for understanding and optimizing the health and welfare of lumpfish and spotted wolffish in aquaculture towards a one health or integrative perspective.

The effects of Pediococcus acidilactici MA18/5M on growth performance, gut integrity, and immune response using in vitro and in vivo Pacific salmonid models

Microbial management is central to aquaculture's efficiency. Pediococcus acidilactici MA18/5M has shown promising results promoting growth, modulation of the immune response, and disease resistance in many fishes. However, the mechanisms through which this strain confers health benefits in fish are poorly understood, particularly in Pacific salmonid models. Briefly, the aims of this study were to i) assess the protective effects of P. acidilactici MA18/5M by examining gut barrier function and the expression of tight junction (TJ) and immune genes in vitro and in vivo, and ii) to determine the protective effects of this strain against a common saltwater pathogen, Vibrio anguillarum J382. An in vitro model of the salmonid gut was employed utilizing the cell line RTgutGC. Barrier formation and integrity assessed by TEER measurements in RTgutGC, showed a significant decrease in resistance in cells exposed only to V. anguillarum J382 for 24 h, but pre-treatment with P. acidilactici MA18/5M for 48 h mitigated these effects. While P. acidilactici MA18/5M did not significantly upregulate tight junction and immune molecules, pre-treatment with this strain protected against pathogen-induced insults to the gut barrier. In particular, the expression of ocldn was significantly induced by V. anguillarum J382, suggesting that this molecule might play a role in the host response against this pathogen. To corroborate these observations in live fish, the effects of P. acidilactici MA18/5M was evaluated in Chinook salmon reared in real aquaculture conditions. Supplementation with P. acidilactici MA18/5M had no effect on Chinook salmon growth parameters after 10 weeks. Interestingly, histopathological results did not show alterations associated with P. acidilactici MA18/5M supplementation, indicating that this strain is safe to be used in the industry. Finally, the expression pattern of transcripts encoding TJ and immune genes in all the treatments suggest that variation in expression is more likely to be due to developmental processes rather than P. acidilactici MA18/5M supplementation. Overall, our results showed that P. acidilactici MA18/5M is a safe strain for use in fish production, however, to assess the effects on growth and immune response previously observed in other salmonid species, an assessment in adult fish is needed.

Comparative Genomic Analysis of a Novel Vibrio sp. Isolated from an Ulcer Disease Event in Atlantic Salmon (Salmo salar)

Ulcer diseases are a recalcitrant issue at Atlantic salmon (Salmo salar) aquaculture cage-sites across the North Atlantic region. Classical ulcerative outbreaks (also called winter ulcer disease) refer to a skin infection caused by Moritella viscosa. However, several bacterial species are frequently isolated from ulcer disease events, and it is unclear if other undescribed pathogens are implicated in ulcer disease in Atlantic salmon. Although different polyvalent vaccines are used against M. viscosa, ulcerative outbreaks are continuously reported in Atlantic salmon in Canada. This study analyzed the phenotypical and genomic characteristics of Vibrio sp. J383 isolated from internal organs of vaccinated farmed Atlantic salmon displaying clinical signs of ulcer disease. Infection assays conducted on vaccinated farmed Atlantic salmon and revealed that Vibrio sp. J383 causes a low level of mortalities when administered intracelomic at doses ranging from 10⁷-10⁸ CFU/dose. Vibrio sp. J383 persisted in the blood of infected fish for at least 8 weeks at 10 and 12 °C. Clinical signs of this disease were greatest 12 °C, but no mortality and bacteremia were observed at 16 °C. The Vibrio sp. J383 genome (5,902,734 bp) has two chromosomes of 3,633,265 bp and 2,068,312 bp, respectively, and one large plasmid of 201,166 bp. Phylogenetic and comparative analyses indicated that Vibrio sp. J383 is related to V. splendidus, with 93% identity. Furthermore, the phenotypic analysis showed that there were significant differences between Vibrio sp. J383 and other Vibrio spp, suggesting J383 is a novel Vibrio species adapted to cold temperatures.