Vibriosis Outbreaks in Aquaculture: Addressing Environmental and Public Health Concerns and Preventive Therapies Using Gilthead Seabream Farming as a Model System

Fire in the belly: Stress and antibiotics induce dysbiosis and inflammation in the gut of common carp

Fish are exposed to numerous stressors which negatively affect their immune response and increase infection susceptibility. The risk of bacterial infections results in the excessive and preventive use of antibiotics. Therefore, we aimed to study how antibiotic treatment and restraint stress will affect the stress response, microbiota composition, gut morphology, and inflammatory reaction in common carp. Both restraint stress and antibiotic treatment increased cortisol level. Moreover, antibiotics induced dysbiosis in fish gut, manifested by a decrease in the total abundance of bacteria, and a shift in bacteria diversity, including a reduced number of Aeromonas, Bacteroides, Barnesiellaceae, Cetobacterium and Shewanella and an increased abundance of Flavobacterium. To a lesser extent, stress modified gut microbiota, as it decreased bacteria number and slightly changed the microbiota composition by decreasing Cetobacterium abundance and increasing Vibrio abundance. Microbiota of the antibiotic-treated and stressed fish shifted from the beneficial bacterial genera - Cetobacterium and Bacteroides, to the increased presence of unfavorable bacteria such as Brevinema, Flavobacterium and Desulfovibrionaceae. Stress and antibiotic-induced changes in the gut microbiota were related to the changes in the gut morphology when the higher abundance of goblet and rodlet cells and increased secretion activity of goblet cells were observed. Moreover, up-regulation of the expression of genes encoding pro-inflammatory mediators and cytokines involved in the Th17 immune response was present in the gut of the antibiotic-treated and stressed fish. We conclude that in carp antibiotics and stress alter the abundance and composition of the microbiota and induce Th17-dependent inflammatory reaction in the gut. Moreover, our results strongly suggest the interplay of the stress axis and the brain-gut-microbiota axis.

Probiotic spore-based antigen delivery: a novel oral vaccine strategy against Vibrio infections in aquaculture

BACKGROUND

Vibriosis is a deadly illness caused by various species of the Vibrio genus. Due to its high incidence in aquaculture plants, vibriosis is responsible for significant economic losses. Currently, anti-vibriosis treatments rely on antibiotics. However, the global rise in antibiotic resistance necessitates the development of alternative approaches. Novel vaccines and effective probiotics have been proposed as potential alternative to antibiotics in fighting bacterial infections. Here we propose a combined vaccine/probiotic strategy based on the use of probiotic bacterial spores for the oral delivery of Vibrio antigens. Spores of various species of the Bacillus genus are widely used as probiotics and have been shown to efficiently display antigens in a non-recombinant way.

RESULTS

Spores of various probiotic strains were analyzed to assess their effectiveness in displaying a heterologous model protein, and B. megaterium MV30 was identified as the most efficient strain. MV30 spores were then used to display two antigens of Vibrio harveyi, the entire Hsp33 protein of 33 kDa and a 239 amino acids fragment of OmpK (OmpK21/260), identified as the most immunogenic part of the protein. While Hsp33 is a stable protein, OmpK21/260 is unstable at conditions mimicking those encountered in an aquaculture plant and the interaction with MV30 spores reduced such instability. The protective ability of the combined probiotic/vaccination strategy was assayed on Medaka fish (Oryzias latipes), as a model. In a challenge experiment with a virulent strain of Vibrio harveyi, a protective effect was observed with MV30 spores alone and such effect was significantly increased when the same spores displayed either one of the two antigens.

CONCLUSION

Our results support the use of probiotics and oral vaccines as a valid alternative to antibiotics and point to the application of probiotic spore-based antigen delivery as a novel strategy to fight pathogenic infections.

Evaluation of a hydrogel platform for encapsulated multivalent Vibrio antigen delivery to enhance immune responses and disease protection against vibriosis in Asian seabass (Lates calcarifer)

This study reports the development and evaluation of a novel multivalent oral hydrogel vaccine designed to protect Asian seabass (Lates calcarifer) against vibriosis caused by multiple Vibrio species. The hydrogel formulation, composed of alginate and bentonite, was engineered to encapsulate three Vibrio pathogens (V. harveyi, V. vulnificus, and P. damsela), and subsequently freeze-dried to yield stable, dry hydrogel beads. Although the process achieved a relatively low yield (approximately 10 %), the dry beads maintained their structural integrity, retained antigenic components with 2.4 ± 1.6 × 107 DNA copies of total cell antigens/mg dry beads, and resisted acidic degradation, ensuring antigen preservation during simulated gastric exposure. Physicochemical characterization (FTIR) confirmed that the encapsulation process preserved the structural and functional properties of alginate, bentonite, and bacterial antigens without introducing new chemical bonds. Scanning electron microscopy (SEM) revealed a porous, sponge-like internal architecture that supported antigen entrapment and controlled release. Under simulated gastric conditions (pH 2.0), the hydrogel exhibited remarkable stability for up to 8 h, preventing antigen loss. Upon transitioning to intestinal conditions (pH 7.2), the matrix gradually disintegrated, releasing the antigens in a controlled manner for up to 8 h. Oral vaccination trials demonstrated enhanced immune responses in Asian seabass. Fish receiving the multivalent Vibrio antigen-containing hydrogel vaccine (Hg-mVibrioAg) displayed elevated serum-specific IgM titers against all three Vibrio species, with significantly higher and more sustained antibody levels following a 7-day and 14-day vaccination regimen. Increased lysozyme and bactericidal activity further supported improved innate defense mechanisms. Subsequent pathogen challenge tests confirmed that vaccinated fish, particularly those following the 7-day and 14-day regimens, exhibited significantly higher survival rates and robust protection. Concurrently, immune-related gene expression in the head kidney, peripheral blood leukocytes, gills, and intestines was upregulated, indicating a broad immune activation associated with specific IgM responses. No significant alterations in blood biochemistry or tissue histology were observed, highlighting the vaccine's biocompatibility. Additionally, these findings underscore the potential of this multivalent oral hydrogel vaccine as a promising, safe, and effective prophylactic strategy against Vibrio infections in Asian seabass aquaculture.

Identification and characterization of Vibrio anguillarum (GA strain) isolated from Obscure Pufferfish Takifugu obscurus

OBJECTIVE

Aquaculture has faced significant challenges due to the emergence of various pathogens affecting fish species. One such species, the Obscure Pufferfish Takifugu obscurus, has experienced high mortality rates due to an outbreak of disease on a fishery farm in Shanghai.

METHODS

The pathogen responsible for this outbreak was isolated and identified as Vibrio anguillarum (GA strain) using a combination of morphological, biochemical, and whole-genome single-nucleotide polymorphism-based phylogenetic analyses. Pathogenicity tests confirmed that the GA strain could cause disease in healthy Obscure Pufferfish, inducing overt hemorrhagic symptoms. Histopathological analysis was performed to assess whether tissue damage had occurred. Whole-genome sequencing revealed that the GA strain possessed 235 virulence genes and two drug resistance-related genes: cyclic AMP receptor protein (CRP) and regulator of secondary metabolites A (rsmA). Testing via PCR further confirmed the presence of 10 common virulence genes.

RESULTS

Antibiotic susceptibility testing showed that the GA strain was highly sensitive to antibiotics such as tetracycline, doxycycline, minocycline, and compound sulfamethoxazole and was resistant to cefradine, cefazolin, penicillin, and vancomycin.

CONCLUSIONS

To the best of our knowledge, this is the first study to report V. anguillarum as the pathogen responsible for this disease in Obscure Pufferfish. The isolate exhibited strong virulence and multidrug resistance. The findings lay the foundation for further disease control in Obscure Pufferfish and the investigation of the epidemiological mechanisms of V. anguillarum.

Glutamicibacter sp. ZY1 antagonizes pathogenic Vibrio parahaemolyticus via iron competition

Probiotics are prior agents for treating bacterial infection with advantages of inhibiting pathogenic bacteria and improving immune responses of hosts, thus increasing the survival rate of cultured animals. In this study, one Vibrio parahaemolyticus YDE17 pathogenic to shrimp and its antagonist Glutamicibacter sp. ZY1 were screened, and ZY1 showed stable inhibitory effects on diverse Vibrio spp., especially V. parahaemolyticus. ZY1 secreted inhibitory substances into supernatant, and the activity of inhibitory substances did not change after being treated under different temperatures, proteinase K, and pH (6-10), which indicated that the inhibitory substances might be small molecules, which led us to trace the siderophore production. The siderophore production of YDE17 co-incubated with the cell-free supernatant of ZY1 was greater than that of YDE17 alone, which indicated that the cell-free supernatant of ZY1 created iron-limiting conditions for YDE17. This finding was confirmed by iron supplementation assays, in which the inhibitory activity of the cell-free supernatant of ZY1 on YDE17 as well as the siderophore production of YDE17 decreased in the presence of FeCl3. The effect of iron on inhibition was further confirmed by in vivo infection. The relative percent survival of ZY1 to shrimp challenged by YDE17 was 83.3%, but the survival rates of shrimp challenged with YDE17/ZY1/FeCl3 were similar to that of YDE17, both of which were significantly lower than the 70% survival rate of shrimps simultaneously challenged by ZY1/YDE17. Our study offers a new probiotic resource to control vibriosis, which works through iron competition with the opportunistic pathogens of Vibrio spp.IMPORTANCEBacteria belonging to Vibrio spp., especially Vibrio parahaemolyticus, are important opportunistic pathogens infecting a wide range of hosts including fish, shrimp, shellfish, and crab. Antibiotics are effective but show the disadvantages of antibiotic generation, microecology destruction, and biological toxicology; thus, new treatments of Vibrio infection are urgently recommended. In our present study, Glutamicibacter sp. ZY1, belonging to the phylum Actinomycetes, was selected and showed high inhibitory activity to inhibit V. parahaemolyticus pathogenic to shrimp. Glutamicibacter sp. ZY1 antagonized V. parahaemolyticus YDE17 through producing siderophore to compete for iron, based on the results of both in vitro and in vivo experiments under different iron levels. This study offers a new strategy to control Vibrio infection in aquaculture.

A suite of ddPCR assays targeting microbial pathogens for improved management of shellfish aquaculture

The shellfish aquaculture industry is one of the fastest-growing sectors of global food production, but it is currently facing major challenges stemming from microbial pathogens. This study presents an optimized and validated suite of droplet digital PCR (ddPCR) assays using water samples proximal to oyster farms in North Carolina to quantify pathogens relevant to the aquaculture industry. Two of the molecular assays enable the quantification of the pathogens, Vibrio parahaemolyticus and Perkinsus marinus, that threaten human health and oyster performance, respectively. This work also introduces two ddPCR assays that enable the simultaneous quantification of at least nine ecologically relevant Vibrio spp. using only two sets of primers and probes targeting the glycosyl hydrolase family 18 (GH18) domain of the chiA gene in Vibrio bacteria. The entire suite of assays was applied to single assessments at 12 sites, revealing heterogeneity in microbial pathogen concentrations across the coastal landscape and variability of abundances within individual estuarine river systems. Additionally, a longitudinal study conducted at a demonstration lease elucidated unique temporal trends for all microbial targets. Notably, when concentrations of Vibrio spp. quantified using the two assays targeting the chiA gene reached their maximum, the daily probability of mortality increased, suggesting a role for other ecologically pertinent Vibrio spp. in the progression of mortality that would otherwise be missed. This study highlights the utility of ddPCR for the advancement of shellfish management by offering insights into the spaciotemporal dynamics of microbial pathogens.

IMPORTANCE

Climate change is drastically altering the environment and changing the abundance and geographical distribution of marine pathogens. These microbial species put additional pressure on the aquaculture industry by acting as sources of disease for animals important to the food industry as well as for humans upon consumption of contaminated food. To address growing concerns, high-resolution monitoring of pathogens can offer insights for effective management in a critical industry. Validated in the field, the suite of molecular droplet digital PCR assays presented here improves upon current methods, enabling the simultaneous quantification of several targets. This technology makes it possible to track pathogens as they move through the environment and reveals changes in abundance that may inform adjustments to farming practices aimed at mitigating negative outcomes. Additionally, this work presents a unique approach to molecular assay design that unveils potential drivers of ecological shifts and emerging etiologies of disease more efficiently.

Evaluation of immune responses and protection in Asian seabass (Lates calcarifer Bloch, 1790) against Vibrio vulnificus using immersion and oral nanoemulsion vaccines

Vaccination is an important strategy in aquaculture for enhancing disease resistance and ensuring the health and productivity of cultured fish. This study investigated the distinct systemic and mucosal immune responses elicited by immersion (ImV) and oral (OrV) nanoemulsion vaccines encapsulating Vibrio vulnificus in Asian seabass (Lates calcarifer). Two vaccination methods, ImV and OrV, were administered to separate groups of Asian seabass, followed by challenges with V. vulnificus via immersion and intraperitoneal (i.p.) injection administration. Immune responses were assessed by measuring specific IgM antibodies, lysozyme activity, bactericidal activity, and immune-related gene expression across multiple organs, including serum, head kidney, liver, gills, skin, and intestine. The results demonstrate that the OrV group had a significantly increased level of specific IgM antibody in their serum, head kidney and liver compared to the immersion vaccine group and control, with the OrV group maintaining higher antibody levels post-immersion and injection challenge. In mucosal tissues, the ImV group elicited stronger IgM responses in the gills and skin, whereas the OrV group enhanced antibody responses in the liver and intestine. Lysozyme and bactericidal activities varied by organ and vaccination route, indicating differential activation of innate immune defenses. Additionally, immune-related gene expression was upregulated in a tissue-specific manner, reflecting the targeted activation of adaptive and innate immune mechanisms by each vaccine type. Both vaccination strategies significantly improved survival and relative percent survival (RPS), with ImV offering stronger protection against immersion challenges, while OrV provided strong protection in systemic (injection) challenges. These findings suggest that ImV and OrV groups induced distinct immune responses in Asian seabass, with immersion vaccination primarily enhancing mucosal immunity at barrier surfaces and oral vaccination promoting systemic and intestinal mucosal immunity. The integration of both vaccination strategies could provide synergistic protection, enhancing vaccine efficacy against V. vulnificus and other pathogens, thereby optimizing disease prevention and fish health management in aquaculture settings.

Vibrio plasmids harboring vhv gene associated with shrimp translucent post-larvae disease: Coexistence of two types of T4SS and multiple transposons

Translucent post-larvae disease (TPD), known as "glass post-larvae disease" is an emerging threat characterized by high mortality rates and severe economic losses. The pathogenesis of TPD has been linked to the Vibrio high virulent (vhv) gene by virulent strains of V. parahaemolyticus. This study presents a comparative genomic analysis of 16 Vibrio plasmids carrying the vhv gene, associated with TPD in shrimp. Specifically, the analysis identified secretion systems and transposons within these plasmids, revealing that all 16 harbor the Type IV Secretion System (T4SS), with distinct T4SS_typeT and T4SS_typeF gene clusters in seven and nine plasmids, respectively. And it was found that the two types of plasmids can coexist within a single bacterial strain. A diverse array of transposons, classified into seven families, was also identified. The study unveils the genetic intricacies of two plasmid types carrying the vhv gene, which are implicated in TPD pathogenesis. The findings underscore the importance of these plasmids' classification based on their secretion systems and highlight their genetic diversity and the presence of transposons, key factors in bacterial adaptability and virulence. This understanding is crucial for developing strategies to mitigate TPD's impact on shrimp aquaculture and ensure food safety.

Occurrence of Vibrio spp. and Pseudomonas spp. Isolates of Nodipecten nodosus (Linnaeus, 1758) and Water from a Mariculture Farm in Angra dos Reis, Brazil

Bivalve mollusks face a crisis due to infectious diseases, resulting in high mortality and economic losses. The need for continuous monitoring to prevent contamination from sewage and rainwater in aquaculture is evident. The recent mass mortality of scallops in Ilha Grande Bay (IGB), Rio de Janeiro's largest scallop producer, due to environmental contaminants underscores the need for further research. This study aims to investigate the recent collapse of the scallop population and assess the human impact by analyzing the circulation of pathogens.

MATERIALS AND METHODS

Mollusks were collected from three sites in Ilha Grande Bay (IGB), a region known for its significant scallop production, and from scallop farms in Angra dos Reis, RJ. A total of 216 gill and adductor tissue samples from lion's foot scallops were analyzed. Bacterial contamination was identified using MALDI-TOF, while antimicrobial susceptibility and carbapenem production were assessed via disk diffusion tests.

RESULTS

Mollusks were contaminated with V. alginolyticus, V. fluvialis, V. harveyi, Pseudomonas putida, and Pseudomonas monteilii. All isolates were sensitive to meropenem, but P. putida showed higher resistance to ciprofloxacin.

CONCLUSIONS

The presence of these pathogenic and resistant bacteria in scallop adductor tissues is a concern for the aquaculture industry and a significant public health risk. The potential for these bacteria to enter the human food chain through consuming contaminated seafood or recreational activities such as bathing is a serious issue that needs to be addressed.

Homologous relationship between FabG involved in fatty acid biosynthesis and SDR on chromosome II in the multi-chromosome pathogen Vibrio anguillarum

Vibrio anguillarum threatens fish and larval farming industries and human health worldwide. The identification of bacterial adaptation and responses to stress due to environmental changes is vital for establishing a response strategy for pathogenic Vibrio. Previously, short-chain dehydrogenase/reductase (SDR) was identified on chromosome II of the multichromosomal V. anguillarum. In this study, a comparison of SDR and the enzyme FabG-1b (encoded on chromosome I and responsible for the β-ketoacyl acyl carrier protein (ACP) reductase in fatty acid biosynthesis (FAS II)) showed that the amino acid sequence homology was only 33.2%; however, the core of functionality, which includes the NAD(P)-binding domain and the conserved region of the active site, the topologies predicted using sequence-based homology modeling, and the quaternary homotetramer-type structures showed a significant similarity. FabG-1b was specific to the substrates fluorinated and halogenated aliphatic ketones, aromatic ketones, and aromatic β-ketoesters and SDR toward non-fluorinated and non-halogenated aliphatic ketones, aromatic ketones, and non-aromatic β-ketoesters. This complementary catalytic efficiencies of the two enzymes on various substrates conclusively supports the hypothesis that the two enzymes are likely homologs. This is the first study to report potential paralogous enzymes FabG-1b and SDR in Vibrio. This information improves our understanding of bacterial FAS for establishing strategies to overcome infectious diseases caused by pathogenic strains and identify targets for developing new antibacterial agents.

Development and Characterization of Fluorescent Protein-Tagged Vibrio harveyi Strains as a Versatile Tool for Studying Infection Dynamics and Strain Interactions

Fluorescent protein-tagged bacterial strains are widely used tools for studying host-pathogen interactions and microbial dynamics. In this study, we developed and characterized Vibrio harveyi strains genetically modified to express green fluorescent protein (GFP) and red fluorescent protein (RFP). These strains were constructed using triparental mating and evaluated for phenotypic, genomic, and virulence attributes. Genomic analyses revealed strain-specific variations, including mutations in key regulatory and metabolic genes, such as luxO and transketolase. While plasmid acquisition imposed metabolic costs, resulting in altered growth and antibiotic sensitivities in certain transconjugants, others demonstrated robust phenotypic stability. Virulence assays using gilthead seabream larvae revealed that most tagged strains retained moderate pathogenicity, with visualization of co-infections highlighting the potential for studying strain-specific interactions. Furthermore, fluorescent microscopy confirmed the successful colonization and localization of tagged bacteria within host tissues. These findings underscore the utility of GFP- and RFP-tagged Vibrio harveyi as versatile tools for infection dynamics, offering a foundation for future research on strain interactions and pathogen-host relationships.

Marine microbes suppressed Vibrio and enhanced biological performance of euryhaline rotifer, Brachionus plicatilis

The excessive use of antibiotics in mariculture has surpassed permitted levels, leading to their release into surrounding waters and accumulation in cultured organisms, which poses risks to human health and highlighting the urgent need for alternatives to reduce antibiotic use. Therefore, the present study aimed to test four microbes including Debaryomyces hansenii, Ruegeria mobilis, Lactobacillus plantarum and Bacillus subtilis, on lowering Vibrio, promoting population increase and survival of Brachionus plicatilis. The digestive enzymes activity including α-amylase, lipase and protease, microbial retention and biochemical composition of rotifers were analyzed. Rotifers with a density of 50 ind/mL were distributed into five treatments (four experimental and a control, quadruplicate, repeated thrice). Each microbe's concentration of 108CFU/mL-1 was applied to the culture condition. L. plantarum and B. subtilis decreased Vibrio and increased the population and survival of rotifers, due to successful colonization, resulting in better nutritional utilization and retention in these groups. Higher enzymatic activity and microbial retention were observed in B. subtilis group. The present findings demonstrate that L. plantarum and B. subtilis could be promising microbes for culture of B. plicatilis to lower Vibrio and ensure higher yields. Identifying a sustainable approach to inhibit Vibrio while enhancing rotifers' performance as the primary food source for marine larviculture is undoubtedly essential.

Microbial Interactions in Rearing Systems for Marine Fish Larvae

This article reviews the scientific literature discussing the microbial interactions between water microbiota, live food microbiota, fish larvae immune system and gut microbiota, and biofilm microbial communities in rearing systems for marine fish larvae. Fish gut microbiota is the first line of defense against opportunistic pathogens, and marine fish larvae are vulnerable to high mortalities during the first weeks after hatching. The bacterial colonization of fish larvae is a dynamic process influenced by environmental and host-related factors. The bacteria transferred to larvae from the eggs can influence the composition of the gut microbiota in the early stages of fish. Fish larvae ingest free-living microorganisms present in the water, as marine fish larvae drink water for osmoregulation. In marine aquaculture systems, the conventional feeding-rearing protocol consists of zooplankton (rotifers, Artemia, and copepods). These live food organisms are filter-feeders. Once transferred to a new environment, they quickly adopt the microflora of the surrounding water. So, the water microbiota is similar to the microbiota of the live food at the time of ingestion of live food by the larvae. In aquaculture rearing systems, bacterial biofilms may harbor opportunistic pathogenic bacteria and serve as a reservoir for those microbes, which may colonize the water column. The methods applied for the study of fish larvae microbiota were reviewed.

Understanding the transfer and persistence of antimicrobial resistance in aquaculture using a model teleost gut system

BACKGROUND

The development, progression, and dissemination of antimicrobial resistance (AMR) are determined by interlinked human, animal, and environmental drivers, which pose severe risks to human and livestock health. Conjugative plasmid transfer drives the rapid dissemination of AMR among bacteria. In addition to the judicious use and implementation of stewardship programs, mitigating the spread of antibiotic resistance requires an understanding of the dynamics of AMR transfer among microbial communities, as well as the role of various microbial taxa as potential reservoirs that promote long-term AMR persistence. Here, we employed Hi-C, a high-throughput, culture-free technique, combined with qPCR, to monitor carriage and transfer of a multidrug-resistent (MDR) plasmid within an Atlantic salmon in vitro gut model during florfenicol treatment, a benzenesulfonyl antibiotic widely deployed in fin-fish aquaculture.

RESULTS

Microbial communities from the pyloric ceaca of three healthy adult farmed salmon were inoculated into three bioreactors simulating the teleost gut, which were developed for the SalmoSim gut system. The model system was then inoculated with the Escherichia coli strain ATCC 25922 carrying the plasmid pM07-1 and treated with florfenicol at a concentration of 150 mg/L in fish feed media for 5 days prior to the washout/recovery phase. Hi-C and metagenomic sequencing identified numerous transfer events, including those involving gram-negative and gram-positive taxa, and, crucially, the transfer and persistence of the plasmid continued once florfenicol treatment was withdrawn.

CONCLUSIONS

Our findings highlight the role of the commensal teleost gut flora as a reservoir for AMR even once antimicrobial selective pressure has been withdrawn. Our system also provides a model to study how different treatment regimens and interventions may be deployed to mitigate AMR persistence.

Exploring single cell microbial protein as a sustainable fishmeal alternative in yellowtail kingfish (Seriola lalandi) diets: impacts on health and gut microbiome

BACKGROUND

With the global expansion of aquaculture and the increasing demand for fish meal, identifying appropriate and sustainable alternative protein sources for aquafeeds has become essential. Single-cell protein (SCP), derived from methanotrophic bacteria, presents a promising alternative by converting methane into protein, potentially addressing both the need for alternative protein sources and reducing industrial greenhouse gas emissions. This study aimed to evaluate the effects of different levels of SCP inclusion (0%, 25%, 50%, and 75% fish meal replacement) on the health, gene expression, and gut microbiome of yellowtail kingfish (YTK, Seriola lalandi) following a 35-day growth trial.

RESULTS

The study found that SCP inclusion at the highest level of fishmeal replacement (75%) induced a mild inflammatory response in the hindgut of the fish. However, micromorphological assessments of the hindgut, serum biochemistry, and gene expression analyses revealed no significant detrimental effects from SCP replacement. Notably, there were indications of improved lipid digestibility with SCP. Furthermore, SCP inclusion significantly enhanced microbial richness and altered the composition of the gut microbiome, introducing beneficial bacterial taxa that may contribute to improved gut health and resilience.

CONCLUSIONS

This study highlights SCP as a viable and sustainable alternative to fish meal in YTK diets. The findings suggest that SCP can be included in YTK diets without adverse health effects at moderate levels and may even offer benefits in terms of lipid digestibility and gut microbiome diversity. These results contribute to the advancement of more sustainable aquaculture practices.

Comprehensive study of Biginelli's compounds show antibacterial activity against Vibrio parahaemolyticus of two strains: In vitro and computational approaches

This study addresses the critical challenges faced by global aquatic industries such as overfishing, habitat destruction, pollution, climate change, and unsustainable aquaculture practices. It focuses on developing effective solutions by synthesizing potent inhibitors against Vibrio parahaemolyticus of two strains namely: MTCC-451 (A) and Vp-S14 (B). Biginelli's compounds (B1-4) were identified as promising inhibitors with confirmed antibacterial activity through in silico and in vitro studies. Then virtual screening through ADMET, best correlation with regard to QSAR studies, the docking analysis is used to determine, the ligand B1 would be more favorable comparable with others for conducting bacterial studies and DFT calculations show that the optimized structure of ligand B1 has the best FMO values, MEP values and appropriate electronic structural state. This research study is very helpful and matches for "Antibacterial analysis". A total of 99 Biginelli compounds were selected for virtual screening including 2D-QSAR, ADME/T, molecular docking, and DFT calculations. The virtual screened compounds were synthesized then for biological studies. The four highlighted compounds (B1-4) with favorable ADME properties and strong binding affinities compared to gentamicin in both ADME and docking analysis respectively. Further analysis via DFT provided structural insights and active site identification. In vitro assays against pathogenic Vp strains demonstrated significant bactericidal activity, with MIC values of 1.25 mg/ml (MTCC-451) and 1 mg/ml (Vp-S14).

Net cage aquaculture alters the co-occurrence network and functions of bacterial communities in offshore areas

A better understanding of bacterial communities and the factors that drive them is essential to maintain their functions and services. As an ecosystem closely linked to human activities, the health of offshore aquaculture depends on the diversity and functions of bacteria in its environment. However, little attention has been paid to the vertical interface of the offshore aquaculture areas with shellfish net cages. In this study, high-throughput sequencing was used to analyze bacterial communities in different water layers of a net cage scallop farm in the offshore area of Northeast of China. Based on the results, an increased richness of bacterial communities was observed in the water adjacent to the net cages. Meanwhile, apparently different bacterial community compositions were observed among the water layers, with an enrichment of Cyanobacteria, Bacteroidota, and Firmicutes in the water layers above, parallel to, and below the net cages, respectively. According to the predicted functions, the bacterial communities of the water layers above, parallel to, and below the net cages were identified as phototrophy-, chemoheterotrophy-, and nitrogen respiration-dominated. Furthermore, network analysis revealed a complex but unstable bacterial community in the water layer containing the net cage. Finally, partial least squares path modelling revealed that the net cage aquaculture directly influenced the environmental variables and bacterial richness, which further induced the variations in bacterial community composition, and ultimately affected their ecological functions. These results provide a basic understanding of bacterial communities in net cage scallop farms and highlight the effects of offshore aquaculture on variations in ecological functions.

Global landscape of Vibrio parahaemolyticus research: a bibliometric analysis

Vibrio parahaemolyticus poses a notable threat to marine ecosystems and can cause infections and disease outbreaks in seafood species, which can affect humans upon consumption. The global impacts of such infections and outbreaks on human and animal health led to a growing number of studies from various countries discussing the prevention, control, treatment, and overall implications of V. parahaemolyticus. Hence, this study aims to retrieve relevant studies on V. parahaemolyticus using a bibliometric analysis to understand current research status, trends, and hotspots regarding this bacteria. Relevant literature was searched across the Scopus database, and the data were subsequently analyzed using Biblioshiny software. In addition, a manual examination was conducted to identify the hosts of V. parahaemolyticus and diseases caused by the bacteria. Overall, 7,096 records were obtained from Scopus from 1963 to 2023. A bibliometric analysis identified 17,220 authors, with China emerging as the global leader. The analysis also highlighted significant keywords such as "Vibrio parahaemolyticus," "Litopenaeus vannamei," and "innate immunity," suggesting a focus on the impact of V. parahaemolyticus on L. vannamei, specifically emphasizing the shrimp's innate immune responses. Host-disease interaction network also uncovered 53 interactions between hosts and diseases involving L. vannamei or Penaeus vannamei as the primary host, with acute hepatopancreas necrosis disease (AHPND) emerging as the most prevalent among them. This study can enhance our understanding of infections caused by V. parahaemolyticus and contribute to the development of effective strategies for their prevention and management.

Highlighting antibiotic-free aquaculture by using marine microbes as a sustainable method to suppress Vibrio and enhance the performance of brine shrimp (Artemia franciscana)

Brine shrimp nauplii are widely used as live food in fish and shellfish aquaculture but they may transmit pathogenic Vibrio to the target species causing significant economic loss. Heavy usage of antibiotics is expensive and environmentally damaging. Use of natural microbes as probiotics for disease management is a more sustainable strategy. In this study the abilities of four marine microbes-Debaryomyces hansenii, Ruegeria mobilis, Lactobacillus plantarum and Bacillus subtilis-to suppress Vibrio spp. and promote growth performance and survival of brine shrimp (Artemia franciscana) were investigated. Nauplii (Instar II) were exposed to 108 CFU mL-1 of one of the four microbes; a control without added microbes was included for comparison. The nauplii were fed daily with the microalga Nannochloropsis oculata. Population change, survival, weight gain, length gain, enzyme activity, microbial retention and body biochemical composition of the brine shrimp were measured. The results showed that B. subtilis and L. plantarum significantly decreased the body loading of Vibrio spp. in A. franciscana. Survival rate, weight gain and length gain of (A) franciscana all increased in L. plantarum and (B) subtilis treatments, but the growth performance in the D. hansenii and R. mobilis treatments was less consistent. Higher lipase and protease activities and lower body ash content in the brine shrimp were observed in the B. subtilis and L. plantarum treatments (P < 0.05). The abundance of B. subtilis in the brine shrimp was relatively stable even after 8 days of starvation. These findings demonstrate that B. subtilis was the most promising probiotic among the tested species, especially for long-term application without the need for repeated inoculation.

Microbial diversity and community structure of microalgae (Nannochloropsis oculata) and rotifer (Brachionus plicatilis) in aquaculture by 16S rRNA amplicon-based sequencing

Live cultures, including Nannochloropsis oculata and Brachionus plicatilis, are essential in aquaculture due to its economic and nutritional value for commercial fish species. Pathogens and probiotics can be introduced to aquaculture systems by live feed, with variations in abundance influenced by environmental physicochemical parameters. To investigate this, amplicon sequencing of the V3-V4 region of the 16S rRNA was conducted using Illumina MiSeq to elucidate bacterial abundances and their variations in response to changes in physicochemical parameters in live feed cultures. Results revealed that pathogens like, Tenacibaculum, predominantly found in rotifer cultures, was inhibited under dissolved oxygen levels of 6.87-8.19 mg/L and pH levels of 8.63-9.23. Winogradskyella, mainly present on day 1 of the microalgae culture, thrived under these same conditions. Potential probiotics were also analyzed. Phaeodactylibacter, primarily found on day 1 of microalgae cultures, was favored by dissolved oxygen levels of 7.11-7.68 mg/L and pH levels of 8.63-9.23 but was inhibited by nitrite levels of 0.46-0.5 mg/L. Overall, dissolved oxygen was the key parameter modulating microbial diversity. This study shows that optimizing environmental parameters can enhance culture health by promoting probiotics and reducing harmful bacteria.

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.

Advances in Vibrio-related infection management: an integrated technology approach for aquaculture and human health

Vibrio species pose significant threats worldwide, causing mortalities in aquaculture and infections in humans. Global warming and the emergence of worldwide strains of Vibrio diseases are increasing day by day. Control of Vibrio species requires effective monitoring, diagnosis, and treatment strategies at the global scale. Despite current efforts based on chemical, biological, and mechanical means, Vibrio control management faces limitations due to complicated implementation processes. This review explores the intricacies and challenges of Vibrio-related diseases, including accurate and cost-effective diagnosis and effective control. The global burden due to emerging Vibrio species further complicates management strategies. We propose an innovative integrated technology model that harnesses cutting-edge technologies to address these obstacles. The proposed model incorporates advanced tools, such as biosensing technologies, the Internet of Things (IoT), remote sensing devices, cloud computing, and machine learning. This model offers invaluable insights and supports better decision-making by integrating real-time ecological data and biological phenotype signatures. A major advantage of our approach lies in leveraging cloud-based analytics programs, efficiently extracting meaningful information from vast and complex datasets. Collaborating with data and clinical professionals ensures logical and customized solutions tailored to each unique situation. Aquaculture biotechnology that prioritizes sustainability may have a large impact on human health and the seafood industry. Our review underscores the importance of adopting this model, revolutionizing the prognosis and management of Vibrio-related infections, even under complex circumstances. Furthermore, this model has promising implications for aquaculture and public health, addressing the United Nations Sustainable Development Goals and their development agenda.

Oleic acid enriched diet affects the metabolome composition of the hybrid grouper infected with vibriosis

This study focuses in investigating the fatty acid contents of surviving infected hybrid grouper fed with oleic acid immunostimulant. After a 6-week feeding trial, Epinephelus fuscoguttatus × Epinephelus lanceolatus fingerlings were infected with Vibrio vulnificus. One week after bacterial challenge, fish oil was extracted from body tissue of surviving infected fingerlings using the Soxhlet extraction method. The extracted samples were then sent for GC-MS analysis. The raw GC-MS data were analyzed using software programs and databases (i.e., MetaboAnalyst, SIMCA-P, NIST Library, and KEGG). A total of 39 metabolites were putatively identified, with 18 metabolites derived from the fatty acid group. Our further analysis revealed that most metabolites were highly abundant in the oleic acid dietary samples, including oleic acid (4.56%), 5,8,11-eicosatrienoic acid (3.45%), n-hexadecenoic acid (3.34%), cis-erucic acid (2.76%), and 9-octadecenoic acid (2.5%). Worthy of note, we observed a greater abundance of α-linoleic acid (15.57%) in the control diet samples than in the oleic acid diet samples (14.59%) with no significant difference in their results. The results obtained from this study revealed that surviving infected hybrid grouper expressed more immune-related fatty acids due to the effect of oleic acid immunostimulant. Therefore, in this study, we propose oleic acid as a potential immunostimulant in enhancing fish immunity in aquaculture industry.

Expression and Immune Response Profiles in Nile Tilapia (Oreochromis niloticus) and European Sea Bass (Dicentrarchus labrax) During Pathogen Challenge and Infection

Nile tilapia (Oreochromis niloticus) and European sea bass (Dicentrarchus labrax) are economically significant species in Mediterranean countries, serving essential roles in the aquaculture industry due to high market demand and nutritional value. They experience substantial losses from bacterial pathogens Vibrio anguillarum and Streptococcus iniae, particularly at the onset of the summer season. The immune mechanisms involved in fish infections by V. anguillarum and S. iniae remain poorly understood. This study investigated their impact through experiments with control and V. anguillarum- and S. iniae-infected groups for each species. Blood samples were collected at 1, 3, and 7 days post bacterial injection to assess biochemical and immunological parameters, including enzyme activities (AST and ALT), oxidative markers (SOD, GPX, CAT, and MDA), and leukocyte counts. Further analyses included phagocyte activity, lysozyme activity, IgM levels, and complement C3 and C4 levels. Muscle tissues were sampled at 1, 3, and 7 days post injection to assess mRNA expression levels of 18 immune-relevant genes. The focus was on cytokines and immune-related genes, including pro-inflammatory cytokines (TNF-α, TNF-β, IL-2, IL-6, IL-8, IL-12, and IFN-γ), major histocompatibility complex components (MHC-IIα and MHC-IIβ), cytokine receptors (CXCL-10 and CD4-L2), antimicrobial peptides (Pleurocidin and β-defensin), immune regulatory peptides (Thymosin β12, Leap 2, and Lysozyme g), and Galectins (Galectin-8 and Galectin-9). β-actin was used as the housekeeping gene for normalization. Significant species-specific responses were observed in N. Tilapia and E. Sea Bass when infected with V. anguillarum and S. iniae, highlighting differences in biochemical, immune, and gene expression profiles. Notably, in N. Tilapia, AST levels significantly increased by day 7 during S. iniae infection, reaching 45.00 ± 3.00 (p < 0.05), indicating late-stage acute stress or tissue damage. Conversely, E. Sea Bass exhibited a significant rise in ALT levels by day 7 in the S. iniae group, peaking at 33.5 ± 3.20 (p < 0.05), suggesting liver distress or a systemic inflammatory response. On the immunological front, N. Tilapia showed significant increases in respiratory burst activity on day 1 for both pathogens, with values of 0.28 ± 0.03 for V. anguillarum and 0.25 ± 0.02 for S. iniae (p < 0.05), indicating robust initial immune activation. Finally, the gene expression analysis revealed a pronounced peak of TNF-α in E. Sea Bass by day 7 post V. anguillarum infection with a fold change of 6.120, suggesting a strong species-specific pro-inflammatory response strategy. Understanding these responses provides critical insights for enhancing disease management and productivity in aquaculture operations.

Insights into the DNA methylation of Portunus trituberculatus in response to Vibrio parahaemolyticus infection

Vibrio parahaemolyticus is the main pathogen causing acute hepatopancreatic necrotic disease in crustaceans. To elucidate the epigenetic regulatory mechanism of crustacean resistance to V. parahaemolyticus infection, we conducted artificial infection studies on Portunus trituberculatus. The results showed that the mortality rate reached the highest at 12 h of artificial infection, which was 23.69 %. At 72 h after V parahaemolyticus infection, the expression level of DNA demethylase (ten-eleven-translocation protein) Tet was significantly decreased, the expression of DNA methyltransferase Dnmt3B fluctuated significantly. Based on the differential expression levels of Tet and Dnmt3B. We depict for DNA methylation profiles of the whole genome of P. trituberculatus at single-base resolution by using whole-genome bisulfite sequencing (WGBS) on hemolymph tissues. The overall DNA methylation level was low at 2.16 % in P. trituberculatus hemolymph. A total of 2590 differentially methylated regions (DMRs) were identified, of which 1329 were hypermethylated and 1261 were hypomethylated, and 1389 genes were annotated in these DMRs. Differently methylated genes (DMGs) were significantly enriched in ribosomes (KO03010), protein kinases (KO01001), cell cycle (HSA04110), endocrine resistance (HSA01522) and FoxO signaling pathway (KO04068). Finally, we selected six differentially methylated genes for quantitative analysis. The results showed that DNA methylation not only has a negative regulatory effect on gene expression, but also has a positive regulatory effect. These results indicated that DNA methylation in the regulation of genes involved in immune responses contributes to the resistance of P. trituberculatus to V. parahaemolyticus, which is valuable for understanding how crustaceans regulate the innate immune system to defend against bacterial infections.

RpoS sigma factor mediates adaptation and virulence in Vibrio mimicus

The alternative sigma factor RpoS functions as a regulator of stress and virulence response in numerous bacterial species. Vibrio mimicus is a critical opportunistic pathogen causing huge losses to aquaculture. However, the exact role of RpoS in V. mimicus remains unclear. In this study, rpoS deletion mutant of V. mimicus was constructed through allelic exchange and the phenotypic and transcriptional changes were investigated to determine the function of RpoS. The abilities of growth, motility, biofilm production, hemolytic activity and pathogenicity were significantly impaired in ΔrpoS strain. Stationary-phase cells of ΔrpoS strain showed lower tolerance to H2O2, heat, ethanol, and starvation stress than the wild-type strain. Transcriptome analyses revealed the involvement of rpoS in various cellular processes, notably bacterial-type flagellum synthesis and assembly, membrane synthesis and assembly and response to various stimuli. Phenotypic and RNA-seq analysis revealed that RpoS is required for biofilm formation, stress resistance, and pathogenicity in V. mimicus. Furthermore, β-galactosidase activity showed that rpoS is essential for optimal transcription of the flgK, fliA, cheA, mcpH mRNA. These results offer significant insight into the function and regulatory network of rpoS/RpoS, thereby improving our understanding and facilitating selection of molecular targets for future prevention strategies against V. mimicus.

Exploring Condition-Specific Variability in the Ureteral Stent Microbiome

(1) Background: Indwelling ureteral stents are commonly used urological devices to maintain ureteral patency, yet they have been associated with complications such as infections. Some studies have shown that bacteria adhere to and create an antimicrobial-resistant biofilm on stents. One factor that may impact biofilm formation is the original condition informing stent placement, such as kidney stones and renal allografts. Both kidney stones and renal allografts are independently associated with infection, yet the differential stent microbiomes of these populations remain poorly characterized. Our objective was to characterize these microbiomes in order to inform urological health practice and help prevent ureteral stent-associated infections. (2) Methods: Stents were collected from kidney stone and renal transplant recipients undergoing routine cystoscopic stent removal. Microbial DNA was extracted from stents and analyzed using 16S Next Generation Sequencing. Descriptive statistics, alpha diversity, and beta diversity methods were used for statistical analysis. (3) Results: The microbiome of ureteral stents in kidney stone and transplant patients is composed of unique species, each with different biofilm-forming abilities. (4) Conclusions: Our findings demonstrate that the microbiome of stents differs based on preceding condition. It is important to conduct future studies that explore this microbiome further to understand what type of stent-associated infection someone may develop based on their initial condition.

The early life microbiome of giant grouper (Epinephelus lanceolatus) larvae in a commercial hatchery is influenced by microorganisms in feed

Fish health, growth and disease is intricately linked to its associated microbiome. Understanding the influence, source and ultimately managing the microbiome, particularly for vulnerable early life-stages, has been identified as one of the key requirements to improving farmed fish production. One tropical fish species of aquaculture importance farmed throughout the Asia-Pacific region is the giant grouper (Epinephelus lanceolatus). Variability in the health and survival of E. lanceolatus larvae is partially dependent on exposure to and development of its early microbiome. Here, we examined the development in the microbiome of commercially reared giant grouper larvae, its surrounding environment, and that from live food sources to understand the type of bacterial species larvae are exposed to, and where some of the sources of bacteria may originate. We show that species richness and microbial diversity of the larval microbiome significantly increased in the first 4 days after hatching, with the community composition continuing to shift over the initial 10 days in the hatchery facility. The dominant larval bacterial taxa appeared to be predominantly derived from live cultured microalgae and rotifer feeds and included Marixanthomonas, Candidatus Hepatincola, Meridianimaribacter and Vibrio. In contrast, a commercial probiotic added as part of the hatchery's operating procedure failed to establish in the larvae microbiome. Microbial source tracking indicated that feed was the largest influence on the composition of the giant grouper larvae microbiome (up to 55.9%), supporting attempts to modulate fish microbiomes in commercial hatcheries through improved diets. The marked abundances of Vibrio (up to 21.7% of 16S rRNA gene copies in larvae) highlights a need for rigorous quality control of feed material.

Application of Nanostructures in Biology and Medicine

At present, nanomaterials are used in a wide range of applications in all spheres of civil needs, including energy, medicine, and industry [...].

Molecular characterization and gene expression of pattern recognition receptors in brown-marbled grouper (Epinephelus fuscoguttatus) fingerlings responding to vibriosis infection

The pathogen recognition system involves receptors and genes that play a crucial role in activating innate immune response in brown-marbled grouper (Epinephelus fuscoguttatus) as a control agent against various infections including vibriosis. Here, we report the molecular cloning of partial open reading frames, sequences characterization, and expression profiles of Pattern Recognition Receptors (PRRs) in brown-marbled grouper. The PRRs, namely pglyrp5, tlr5, ctlD, and ctlE in brown-marbled grouper, possess conserved domains and showed shared evolutionary relationships with other fishes, humans, mammals, birds, reptilians, amphibians, and insects. In infection experiments, up to 50% mortality was found in brown-marbled grouper fingerlings infected with Vibrio alginolyticus compared to 27% mortality infected Vibrio parahaemolyticus and 100% survival of control groups. It is also demonstrated that all four PRRs had higher expression in samples infected with V. alginolyticus compared to V. parahaemolyticus. This PRRs gene expression analysis revealed that all four PRRs expressed rapidly at 4-h post-inoculation even though the Vibrio count was only detected earliest at 12-h post-inoculation in samples. The highest expression recorded was from V. alginolyticus inoculated fish spleen with up to 73-fold change for pglyrp5 gene, followed by 14 to 38-fold expression for the same treatment in spleen, head kidney, and blood samples for other PRRs, namely tlr5, ctlD, and ctlE genes. Meanwhile less than a 10% increase in expression of all four genes was detected in spleen, head kidney, and blood samples inoculated with V. parahaemolyticus. These findings indicated that pglyrp5, tlr5, ctlD, and ctlE play important roles in the early immune response to vibriosis infected, brown-marbled grouper fingerlings.

Current approaches to genetic modification of marine bacteria and considerations for improved transformation efficiency

Marine bacteria play vital roles in symbiosis, biogeochemical cycles and produce novel bioactive compounds and enzymes of interest for the pharmaceutical, biofuel and biotechnology industries. At present, investigations into marine bacterial functions and their products are primarily based on phenotypic observations, -omic type approaches and heterologous gene expression. To advance our understanding of marine bacteria and harness their full potential for industry application, it is critical that we have the appropriate tools and resources to genetically manipulate them in situ. However, current genetic tools that are largely designed for model organisms such as E. coli, produce low transformation efficiencies or have no transfer ability in marine bacteria. To improve genetic manipulation applications for marine bacteria, we need to improve transformation methods such as conjugation and electroporation in addition to identifying more marine broad host range plasmids. In this review, we aim to outline the reported methods of transformation for marine bacteria and discuss the considerations for each approach in the context of improving efficiency. In addition, we further discuss marine plasmids and future research areas including CRISPR tools and their potential applications for marine bacteria.

Whole-genome sequencing of Pseudoalteromonas piscicida 2515 revealed its antibacterial potency against Vibrio anguillarum: a preliminary invitro study

Pseudoalteromonas piscicida 2515, isolated from Litopenaeus vannamei culture water, is a potential marine probiotic with broad anti-Vibrio properties. However, genomic information on P. piscicida 2515 is scarce. In this study, the general genomic characteristics and probiotic properties of the P. piscicida 2515 strain were analysed. In addition, we determined the antibacterial mechanism of this bacterial strain by scanning electron microscopy (SEM). The results indicated that the whole-genome sequence of P. piscicida 2515 contained one chromosome and one plasmid, including a total length of 5,541,406 bp with a G + C content of 43.24%, and 4679 protein-coding genes were predicted. Various adhesion-related genes, amino acid and vitamin metabolism and biosynthesis genes, and stress-responsive genes were found with genome mining tools. The presence of genes encoding chitin, bromocyclic peptides, lantibiotics, and sactipeptides showed the strong antibacterial activity of the P. piscicida 2515 strain. Moreover, in coculture with Vibrio anguillarum, P. piscicida 2515 displayed vesicle/pilus-like structures located on its surface that possibly participated in its bactericidal activity, representing an antibacterial mechanism. Additionally, 16 haemolytic genes and 3 antibiotic resistance genes, including tetracycline, fluoroquinolone, and carbapenem were annotated, but virulence genes encoding enterotoxin FM (entFM), cereulide (ces), and cytotoxin K were not detected. Further tests should be conducted to confirm the safety characteristics of P. piscicida 2515, including long-term toxicology tests, ecotoxicological assessment, and antibiotic resistance transfer risk assessment. Our results here revealed a new understanding of the probiotic properties and antibacterial mechanism of P. piscicida 2515, in addition to theoretical information for its application in aquaculture.

Bacteriophages to control Vibrio alginolyticus in live feeds prior to their administration in larviculture

AIMS

This study aimed to evaluate the efficiency of two phages [VB_VaC_TDDLMA (phage TDD) and VB_VaC_SRILMA (phage SRI)] alone and in a cocktail to control Vibrio alginolyticus in brine shrimp before their administration in larviculture.

METHODS AND RESULTS

Phages were isolated from seawater samples and characterized by host spectrum, growth parameters, adsorption rate, genomic analysis, and inactivation efficiency. Both phages belong to the Caudoviricetes class and lack known virulence or antibiotic-resistance genes. They exhibit specificity, infecting only their host, V. alginolyticus CECT 521. Preliminary experiments in a culture medium showed that phage TDD (reduction of 5.8 log CFU ml-1 after 10 h) outperformed phage SRI (reduction of 4.6 log CFU ml-1 after 6 h) and the cocktail TDD/SRI (reduction of 5.2 log CFU ml-1 after 8 h). In artificial marine water experiments with Artemia franciscana, both single phage suspensions and the phage cocktail, effectively inactivated V. alginolyticus in culture water (reduction of 4.3, 2.1, and 1.9 log CFU ml-1 for phages TDD, SRI, and the phage cocktail, respectively, after 12 h) and in A. franciscana (reduction of 51.6%, 87.3%, and 85.3% for phages TDD, SRI, and the phage cocktail, respectively, after 24 h). The two phages and the phage cocktail did not affect A. franciscana natural microbiota or other Vibrio species in the brine shrimp.

CONCLUSIONS

The results suggest that phages can safely and effectively control V. alginolyticus in A. franciscana prior to its administration in larviculture.

Harnessing the intragenomic variability of rRNA operons to improve differentiation of Vibrio species

Although the 16S rRNA gene is frequently used as a phylogenetic marker in analysis of environmental DNA, this marker often fails to distinguish closely related species, including those in the genus Vibrio. Here, we investigate whether inclusion and analysis of 23S rRNA sequence can help overcome the intrinsic weaknesses of 16S rRNA analyses for the differentiation of Vibrio species. We construct a maximum likelihood 16S rRNA gene tree to assess the use of this gene to identify clades of Vibrio species. Within the 16S rRNA tree, we identify the putative informative bases responsible for polyphyly, and demonstrate the association of these positions with tree topology. We demonstrate that concatenation of 16S and 23S rRNA genes increases the number of informative nucleotide positions, thereby overcoming ambiguities in 16S rRNA-based phylogenetic reconstructions. Finally, we experimentally demonstrate that this approach considerably improves the differentiation and identification of Vibrio species in environmental samples.

An In-Depth Study on the Inhibition of Quorum Sensing by Bacillus velezensis D-18: Its Significant Impact on Vibrio Biofilm Formation in Aquaculture

Amid growing concerns about antibiotic resistance, innovative strategies are imperative in addressing bacterial infections in aquaculture. Quorum quenching (QQ), the enzymatic inhibition of quorum sensing (QS), has emerged as a promising solution. This study delves into the QQ capabilities of the probiotic strain Bacillus velezensis D-18 and its products, particularly in Vibrio anguillarum 507 communication and biofilm formation. Chromobacterium violaceum MK was used as a biomarker in this study, and the results confirmed that B. velezensis D-18 effectively inhibits QS. Further exploration into the QQ mechanism revealed the presence of lactonase activity by B. velezensis D-18 that degraded both long- and short-chain acyl homoserine lactones (AHLs). PCR analysis demonstrated the presence of a homologous lactonase-producing gene, ytnP, in the genome of B. velezensis D-18. The study evaluated the impact of B. velezensis D-18 on V. anguillarum 507 growth and biofilm formation. The probiotic not only controls the biofilm formation of V. anguillarum but also significantly restrains pathogen growth. Therefore, B. velezensis D-18 demonstrates substantial potential for preventing V. anguillarum diseases in aquaculture through its QQ capacity. The ability to disrupt bacterial communication and control biofilm formation positions B. velezensis D-18 as a promising eco-friendly alternative to conventional antibiotics in managing bacterial diseases in aquaculture.

Screening of Microalgae for Bioactivity with Antiviral, Antibacterial, Anti-Inflammatory and Anti-Cancer Assays

Marine microalgae are a rich reservoir of natural compounds, including bioactives. Nonetheless, these organisms remain fairly unexplored despite their potential biotechnological applications. Culture collections with diverse taxonomic groups and lifestyles are a good source to unlock this potential and discover new molecules for multiple applications such as the treatment of human pathologies or the production of aquaculture species. In the present work extracts from thirty-three strains (including twenty dinoflagellates, four diatoms and nine strains from seven other algal classes), cultivated under identical conditions, were examined for their antiviral, antibacterial, anti-inflammatory and anti-cancer activities. Among these, antiviral and anti-inflammatory activities were detected in a few strains while the antibacterial tests showed positive results in most assays. In turn, most trials did not show any anti-cancer activity. Significant differences were observed between species within the same class, in particular dinoflagellates, which were better represented in this study. These preliminary findings pave the way for an in-depth characterization of the extracts with highest signals in each test, the identification of the compounds responsible for the biological activities found and a further screening of the CCVIEO culture collection.

Antagonistic activity of Phaeobacter piscinae against the emerging fish pathogen Vibrio crassostreae in aquaculture feed algae

Aquaculture provides a rich resource of high-quality protein; however, the production is challenged by emerging pathogens such as Vibrio crassostreae. While probiotic bacteria have been proposed as a sustainable solution to reduce pathogen load in aquaculture, their application requires a comprehensive assessment across the aquaculture food chain. The purpose of this study was to determine the antagonistic effect of the potential probiotic bacterium Phaeobacter piscinae against the emerging fish pathogen V. crassostreae in aquaculture feed algae that can be an entry point for pathogens in fish and shellfish aquaculture. P. piscinae strain S26 produces the antibacterial compound tropodithietic acid (TDA). In a plate-based assay, P. piscinae S26 was equally to more effective than the well-studied Phaeobacter inhibens DSM17395 in its inhibition of the fish pathogens Vibrio anguillarum 90-11-286 and V. crassostreae DMC-1. When co-cultured with the microalgae Tetraselmis suecica and Isochrysis galbana, P. piscinae S26 reduced the maximum cell density of V. crassostreae DMC-1 by 2 log and 3-4 log fold, respectively. A TDA-deficient mutant of P. piscinae S26 inhibited V. crassostreae DMC-1 to a lesser extent than the wild type, suggesting that the antagonistic effect involves TDA and other factors. TDA is the prime antagonistic agent of the inhibition of V. anguillarum 90-11-286. Comparative genomics of V. anguillarum 90-11-286 and V. crassostreae DMC-1 revealed that V. crassostreae DMC-1 carries a greater arsenal of antibiotic resistance genes potentially contributing to the reduced effect of TDA. In conclusion, P. piscinae S26 is a promising new candidate for inhibition of emerging pathogens such as V. crassostreae DMC-1 in algal feed systems and could contribute to a more sustainable aquaculture industry.IMPORTANCEThe globally important production of fish and shellfish in aquaculture is challenged by disease outbreaks caused by pathogens such as Vibrio crassostreae. These outbreaks not only lead to substantial economic loss and environmental damage, but treatment with antibiotics can also lead to antibiotic resistance affecting human health. Here, we evaluated the potential of probiotic bacteria, specifically the newly identified strain Phaeobacter piscinae S26, to counteract these threats in a sustainable manner. Through a systematic assessment of the antagonistic effect of P. piscinae S26 against V. crassostreae DMC-1, particularly within the context of algal feed systems, the study demonstrates the effectiveness of P. piscinae S26 as probiotic and thereby provides a strategic pathway for addressing disease outbreaks in aquaculture. This finding has the potential of significantly contributing to the long-term stability of the industry, highlighting the potential of probiotics as an efficient and environmentally conscious approach to safeguarding aquaculture productivity against the adverse impact of pathogens.

In Vitro Profiling of Potential Fish Probiotics, Enterococcus hirae Strains, Isolated from Jade Perch, and Safety Properties Assessed Using Whole Genome Sequencing

The demands of intensified aquaculture production and escalating disease prevalence underscore the need for efficacious probiotic strategies to enhance fish health. This study focused on isolating and characterising potential probiotics from the gut microbiota of the emerging aquaculture species jade perch (Scortum barcoo). Eighty-seven lactic acid bacteria and 149 other bacteria were isolated from the digestive tract of five adult jade perch. The screening revealed that 24 Enterococcus hirae isolates inhibited the freshwater pathogens Aeromonas sobria and Streptococcus iniae. Co-incubating E. hirae with the host gut suspensions demonstrated a two- to five-fold increase in the size of growth inhibition zones compared to the results when using gut suspensions from tilapia (a non-host), indicating host-specificity. Genome analysis of the lead isolate, E. hirae R44, predicted the presence of antimicrobial compounds like enterolysin A, class II lanthipeptide, and terpenes, which underlay its antibacterial attributes. Isolate R44 exhibited desirable probiotic characteristics, including survival at pH values within the range of 3 to 12, bile tolerance, antioxidant activity, ampicillin sensitivity, and absence of transferable antimicrobial resistance genes and virulence factors commonly associated with hospital Enterococcus strains (IS16, hylEfm, and esp). This study offers a foundation for sourcing host-adapted probiotics from underexplored aquaculture species. Characterisation of novel probiotics like E. hirae R44 can expedite the development of disease mitigation strategies to support aquaculture intensification.

Unravelling the genomic secrets of bacterial fish pathogens: a roadmap to aquaculture sustainability

In the field of aquaculture, bacterial pathogens pose significant challenges to fish health and production. Advancements in genomic technologies have revolutionized our understanding of bacterial fish pathogens and their interactions with their host species. This review explores the application of genomic approaches in the identification, classification, and characterization of bacterial fish pathogens. Through an extensive analysis of the literature, we have compiled valuable data on 79 bacterial fish pathogens spanning 13 different phyla, encompassing their whole genome sequences. By leveraging high-throughput sequencing techniques, researchers have gained valuable insights into the genomic makeup of these pathogens, enabling a deeper understanding of their virulence factors and mechanisms of host interaction. Furthermore, genomic approaches have facilitated the discovery of potential vaccine and drug targets, opening up new avenues for the development of effective interventions against fish pathogens. Additionally, the utilization of genomics in fish disease resistance and control in aquaculture has shown promising results, enabling the identification of genetic markers associated with disease resistance traits. This review highlights the significant contributions of genomics to the field of fish pathogen research and underscores its potential for improving disease management strategies and enhancing the sustainability of aquaculture practices.

Transcriptome analysis reveals tissue-specific responses of Mytilus unguiculatus to Vibrio alginolyticus infection

Mytilus unguiculatus is an important economic bivalve species with wide consumption and aquaculture value. Disease is one of the primary limiting factors in mussel aquaculture, thus understanding the response of different tissues of M. unguiculatus to pathogens is crucial for disease prevention and control. In this study, we investigated the physiological and transcriptomic responses of the gills, adductor muscle, and mantle of M. unguiculatus infected with Vibrio alginolyticus. The results showed that V. alginolyticus infection caused inflammation and tissue structure changes in the gill, adductor muscle and mantle of M. unguiculatus. Meanwhile, the activities of superoxide dismutase and catalase in the three tissues increased, while the total antioxidant capacity decreased, suggesting that M. unguiculatus have an activated defense mechanism against infection-induced oxidative stress, despite a compromised total antioxidant capacity. Transcriptomic studies reveal that infected M. unguiculatus exhibits upregulation of endocytosis, lysosome activity, cellular apoptosis, and immune-related signaling pathways, indicating that M. unguiculatus responds to pathogen invasion by upregulating efferocytosis. Compared with the gill and adductor muscle, the mantle had a higher level of mytimycin, mytilin and myticin, and the three tissues also increased the expression of mytimycin to cope with the invasion of pathogens. In addition, the analysis of genes related to taste transduction pathways and muscle contraction and relaxation found that after infection with V. alginolyticus, M. unguiculatus may reduce appetite by inhibiting taste transduction in the gill, while improving muscle contraction of the adductor muscle and keeping the shell closed, to resist further invasion of pathogens and reduce the risk of pathogen transmission in the population.

Marine diseases and the Anthropocene: Understanding microbial pathogenesis in a rapidly changing world

Healthy marine ecosystems are paramount for Earth's biodiversity and are key to sustaining the global economy and human health. The effects of anthropogenic activity represent a pervasive threat to the productivity of marine ecosystems, with intensifying environmental stressors such as climate change and pollution driving the occurrence and severity of microbial diseases that can devastate marine ecosystems and jeopardise food security. Despite the potentially catastrophic outcomes of marine diseases, our understanding of host-pathogen interactions remains an understudied aspect of both microbiology and environmental research, especially when compared to the depth of information available for human and agricultural systems. Here, we identify three avenues of research in which we can advance our understanding of marine disease in the context of global change, and make positive steps towards safeguarding marine communities for future generations.

Oxidative stress, gene expression and histopathology of cultured gilthead sea bream (Sparus aurata) naturally co-infected with Ergasilus sieboldi and Vibrio alginolyticus

BACKGROUND

Parasitic and bacterial co-infections have been associated with increasing fish mortalities and severe economic losses in aquaculture through the past three decades. The aim of this study was to evaluate the oxidative stress, histopathology, and immune gene expression profile of gilthead sea bream (Sparus aurata) co-infected with Ergasilus sieboldi and Vibrio alginolyticus.

RESULTS

Vibrio alginolyticus and Ergasilus sieboldi were identified using 16 S rRNA and 28 S rRNA sequencing, respectively. The collagenase virulence gene was found in all Vibrio alginolyticus isolates, and the multiple antimicrobial resistance index ranged from 0.286 to 0.857. Oxidant-antioxidant parameters in the gills, skin, and muscles of naturally infected fish revealed increased lipid peroxidation levels and a decrease in catalase and glutathione antioxidant activities. Moreover, naturally co-infected gilthead sea bream exhibited substantial up-regulation of il-1β, tnf-α, and cyp1a1. Ergasilus sieboldi encircled gill lamellae with its second antennae, exhibited severe gill architectural deformation with extensive eosinophilic granular cell infiltration. Vibrio alginolyticus infection caused skin and muscle necrosis in gilthead sea bream.

CONCLUSION

This study described some details about the gill, skin and muscle tissue defense mechanisms of gilthead sea bream against Ergasilus sieboldi and Vibrio alginolyticus co-infections. The prevalence of co-infections was 100%, and no resistant fish were detected. These co-infections imbalance the health status of the fish by hampering the oxidant-antioxidant mechanisms and proinflammatory/inflammatory immune genes to a more detrimental side. Our results suggest that simultaneous screening for bacterial and parasitic pathogens should be considered.

Vibrio alginolyticus growth kinetics and the metabolic effects of iron

IMPORTANCE

Transmission of V. alginolyticus occurs opportunistically through direct seawater exposure and is a function of its abundance in the environment. Like other Vibrio spp., V. alginolyticus are considered conditionally rare taxa in marine waters, with populations capable of forming large, short-lived blooms under specific environmental conditions, which remain poorly defined. Prior research has established the importance of temperature and salinity as the major determinants of Vibrio geographical and temporal range. However, bloom formation can be strongly influenced by other factors that may be more episodic and localized, such as changes in iron availability. Here we confirm the broad temperature and salinity tolerance of V. alginolyticus and demonstrate the importance of iron supplementation as a key factor for growth in the absence of thermal or osmotic stress. The results of this research highlight the importance of episodic iron input as a crucial metric to consider for the assessment of V. alginolyticus risk.

In Vitro Efficacy of Isobutyl Cyanoacrylate Nanoparticles against Fish Bacterial Pathogens and Selection Preference by Rainbow Trout (Oncorhynchus mykiss)

The upsurge in havoc being wreaked by antibiotic-resistant bacteria has led to an urgent need for efficacious alternatives to antibiotics. This study assessed the antibacterial efficacy of two isobutyl cyanoacrylate nanoparticles (iBCA-NPs), D6O and NP30, against major bacterial pathogens of fish. In vivo tests on rainbow trout were preceded by in vitro tests of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). NP30 exhibited higher efficacy than D60, but both iBCA-NPs demonstrated dose-dependent and species-specific in vitro antibacterial properties against the bacterial isolates. Generally, Gram-negative bacteria were more resistant to the iBCA-NPs. Streptococcus iniae, Tenacibaculum maritimum, and Photobacterium damselae were particularly sensitive to both iBCA-NPs. Administered to rainbow trout at 3571.4 mg (iBCA-NP)/kg feed, the iBCA-NPs produced a relative gain rate and survival rates comparable to the control (p > 0.05). The condition factor and the hepatosomatic and viscerosomatic indices of fish were indifferentiable (p > 0.05) between the iBCA-NP groups and the control. The iBCA-NPs caused no alteration in stress, oxidative stress (superoxide dismutase, SOD), plasma complement titer, or lysozyme activity. This study presents the first report of antibacterial activity of iBCA-NPs against Gram-negative bacteria. The results of this study suggest that D60 and NP30 may contribute to reducing the amounts of antibiotics and chemotherapeutic agents used in aquaculture.

Aeromonashydrophila infection in tilapia triggers changes in the microbiota composition of fish internal organs

Aeromonas hydrophila is a major pathogenic species that causes mass mortality in various freshwater fish species including hybrid tilapia, the main fish species in Israeli aquaculture. Our hypothesis was that A. hydrophila infection may cause changes in the microbiota composition of fish internal organs, and therefore we aimed to study the effect of A. hydrophila infection by injection or by net handling on the microbiota compositions of fish intestine, spleen, and liver. Significant differences in the microbiota composition were found between the internal organs of the diseased and the healthy fish in both experimental setups. Fusobacteriota was the most dominant phylum in the microbiota of healthy fish (∼70%, liver). Cetobacterium was the most abundant genus and relatively more abundant in healthy, compared to diseased fish. When A. hydrophila was inoculated by injection, it was the only pathogenic genus in the spleen and liver of the diseased fish. However, in the handling experiment, Vibrio was also detected in the diseased fish, demonstrating coinfection interactions. Based on these experiments, we conclude that indeed, A. hydrophila infection in tilapia causes changes in the microbiota composition of fish internal organs, and that fish net handling may trigger bacterial infection in freshwater aquaculture.

Insights into molecular aspects of pathogenesis and disease management in acute hepatopancreatic necrosis disease (AHPND): An updated review

Shrimp aquaculture is a rapidly growing sector that makes a significant economic contribution. However, the aquaculture industry is confronted with significant challenges, and infectious diseases, notably Acute Hepatopancreatic Necrosis Disease (AHPND), have emerged as severe threat. AHPND is caused by pathogens carrying the pVA-1 plasmid, which expresses the PirAB toxin, and it has wreaked havoc in shrimp aquaculture, imposing substantial economic burdens. To address this issue, it is crucial to delve into shrimp's immune responses. Therefore, this comprehensive review offers an in-depth examination of AHPND outbreaks, encompassing various facets such as environmental factors, host susceptibility, and the mechanisms employed by the pathogens. Traditional approaches to combat AHPND, primarily relying on chemicals and antibiotics, have raised concerns related to antibiotic resistance and have demonstrated limited success in disease control. Hence this review spotlights recent advancements in molecular diagnostics, therapeutic agents, and research related to shrimp immunity. Understanding these developments is crucial in the ongoing battle against AHPND. In conclusion, this review underscores the pressing need to comprehend the underlying mechanisms of AHPND pathogenesis and emphasizes the importance of developing comprehensive and effective solutions to combat this devastating disease, which continues to threaten the sustainability of shrimp farming.

Tools to Enumerate and Predict Distribution Patterns of Environmental Vibrio vulnificus and Vibrio parahaemolyticus

Vibrio vulnificus (Vv) and Vibrio parahaemolyticus (Vp) are water- and foodborne bacteria that can cause several distinct human diseases, collectively called vibriosis. The success of oyster aquaculture is negatively impacted by high Vibrio abundances. Myriad environmental factors affect the distribution of pathogenic Vibrio, including temperature, salinity, eutrophication, extreme weather events, and plankton loads, including harmful algal blooms. In this paper, we synthesize the current understanding of ecological drivers of Vv and Vp and provide a summary of various tools used to enumerate Vv and Vp in a variety of environments and environmental samples. We also highlight the limitations and benefits of each of the measurement tools and propose example alternative tools for more specific enumeration of pathogenic Vv and Vp. Improvement of molecular methods can tighten better predictive models that are potentially important for mitigation in more controlled environments such as aquaculture.

Comprehensive study on the effect of dietary leucine supplementation on intestinal physiology, TOR signaling and microbiota in juvenile turbot (Scophthalmus maximus L.)

Intestinal damage and inflammation are major health and welfare issues in aquaculture. Considerable efforts have been devoted to enhancing intestinal health, with a specific emphasis on dietary additives. Branch chain amino acids, particularly leucine, have been reported to enhance growth performance in various studies. However, few studies have focused on the effect of leucine on the intestinal function and its underlying molecular mechanism is far from fully illuminated. In the present study, we comprehensively evaluated the effect of dietary leucine supplementation on intestinal physiology, signaling transduction and microbiota in fish. Juvenile turbot (Scophthalmus maximus L.) (10.13 ± 0.01g) were fed with control diet (Con diet) and leucine supplementation diet (Leu diet) for 10 weeks. The findings revealed significant improvements in intestinal morphology and function in the turbot fed with Leu diet. Leucine supplementation also resulted in a significant increase in mRNA expression levels of mucosal barrier genes, indicating enhanced intestinal integrity. The transcriptional levels of pro-inflammatory factors il-1β, tnf-α and irf-1 was decreased in response to leucine supplementation. Conversely, the level of anti-inflammatory factors tgf-β, il-10 and nf-κb were up-regulated by leucine supplementation. Dietary leucine supplementation led to an increase in intestinal complement (C3 and C4) and immunoglobulin M (IgM) levels, along with elevated antioxidant activity. Moreover, dietary leucine supplementation significantly enhanced the postprandial phosphorylation level of the target of rapamycin (TOR) signaling pathway in the intestine. Finally, intestinal bacterial richness and diversity were modified and intestinal bacterial composition was re-shaped by leucine supplementation. Overall, these results provide new insights into the beneficial role of leucine supplementation in promoting intestinal health in turbot, offering potential implications for the use of leucine as a nutritional supplement in aquaculture practices.

Management and Mitigation of Vibriosis in Aquaculture: Nanoparticles as Promising Alternatives

Vibriosis is one of the most common diseases in marine aquaculture, caused by bacteria belonging to the genus Vibrio, that has been affecting many species of economically significant aquatic organisms around the world. The prevention of vibriosis in aquaculture is difficult, and the various treatments for vibriosis have their limitations. Therefore, there is an imperative need to find new alternatives. This review is based on the studies on vibriosis, specifically on the various treatments and their limitations, as well as the application of nanoparticles in aquaculture. One of the promising nanoparticles is graphene oxide (GO), which has been used in various applications, particularly in biological applications such as biosensors, drug delivery, and potential treatment for infectious diseases. GO has been shown to have anti-bacterial properties against both Gram-positive and Gram-negative bacteria, but no research has been published that emphasizes its impact on Vibrio spp. The review aims to explore the potential use of GO for treatment against vibriosis.

Hepcidin and piscidin modulation and antibacterial response in gilthead seabream (Sparus aurata) infected with Vibrio harveyi

Vibriosis is an infectious disease that generates large economic losses in Mediterranean aquaculture. Vibrio harveyi is one of the marine bacteria causing this disease, it is widespread in the Mediterranean Sea and causes ulcers on the skin of the fish it infects. In addition, the skin is a route of entry and colonization of this pathogen. In this study, one group of fish was injected intraperitoneally with phosphate buffered saline (control group) and another with V. harveyi (infected group). At 4 h after injection, samples of skin mucus, blood, skin, head kidney, liver, and spleen were collected to study the immune response generated. Liver histology showed notable alterations in hepatocyte morphology, such as increased vacuolization. Bactericidal activity was measured in skin mucus and serum against V. harveyi and V. anguillarum, different changes in this activity were recorded depending on the bacteria target and sample (skin mucus or serum) used. Gene expression of genes encoding hepcidins and piscidins (antimicrobial peptides) was performed in the mentioned organs. The results indicated a different expression according to the type of AMP and the tissue studied. Hepcidin appeared involved in all tissues studied while piscidins were in the spleen. In this study we have integrated hepcidin-piscidin modulation with the effects of infection on skin mucosa, serum and hepatocyte morphology. Knowing the changes produced in all these parameters improves the understanding of the infection in the first hours in sea bream and could have applications in the diagnosis or treatment of vibriosis in fish farms.