Vibrio Alginolyticus Research Articles

Enhancement of immunity and disease resistance in Litopenaeus vannamei through injection of tyramine formulated with polyethylene glycol

This study investigates the prolonged effect of immune disease resistance in Litopenaeus vannamei through the administration of tyramine (TA) formulated with polyethylene glycol (PEG). Facing the challenges of intensive farming, environmental stress, and global climate changes, innovative approaches to improve shrimp health are essential. The research focuses on the role of biogenic amines in stress response and immune regulation, demonstrating that TA, especially when combined with PEG, significantly prolongs immunity and resistance against Vibrio alginolyticus. The experimental design included administering TA, PEG, and TA-PEG, followed by evaluations of immunity, lactate and glucose levels, and immune-related gene expressions. Results showed notable prolonged effects in total hemocyte count, phenoloxidase activity, and phagocytic activity in the TA-PEG group, indicating enhanced immune activation period. Additionally, the expression of prophenoloxidase system-related genes was significantly upregulated in the TA-PEG group. Furthermore, the TA-PEG group exhibited a significantly higher survival rate in a susceptibility test against V. alginolyticus. The results of this study confirm that the combined use of PEG can effectively extend the immunostimulatory duration of TA.

Isolation and Characterization of a Novel Phage against Vibrio alginolyticus Belonging to a New Genus.

Vibrio alginolyticus causes substantial economic losses in the aquaculture industry. With the rise of multidrug-resistant Vibrio strains, phages present a promising solution. Here, a novel lytic Vibrio phage, vB_ValC_RH2G (RH2G), that efficiently infects the pathogenic strain V. alginolyticus ATCC 17749T, was isolated from mixed wastewater from an aquatic market in Xiamen, China. Transmission electron microscopy revealed that RH2G has the morphology of Siphoviruses, featuring an icosahedral head (73 ± 2 nm diameter) and long noncontractile tail (142 ± 4 nm). A one-step growth experiment showed that RH2G had a short latent period (10 min) and a burst size of 48 phage particles per infected cell. Additionally, RH2G was highly species-specific and was relatively stable at 4-55 °C and pH 4-10. A genomic analysis showed that RH2G has a 116,749 bp double-stranded DNA genome with 43.76% GC content. The intergenomic similarity between the genome sequence of RH2G and other phages recorded in the GenBank database was below 38.8%, suggesting that RH2G represents a new genus. RH2G did not exhibit any virulence or resistance genes. Its rapid lysis capacity, lytic activity, environmental resilience, and genetic safety suggested that RH2G may be a safe candidate for phage therapy in combatting vibriosis in aquaculture settings.

Graphitic carbon nitride loaded with FeOOH quantum dots for synergistic photocatalysis-Fenton inactivation of pathogenic marine bacteria: Mechanisms and coupling coefficients

Sustainable and environmental benign technologies for inactivation of pathogenic marine bacteria in ballast water remains a challenge. Herein, graphitic carbon nitride (g-C3N4) loaded with FeOOH quantum dots (QDs) were fabricated and a synergistic photocatalysis-Fenton system was established, which inactivated Vibrio alginolyticus (7 log) in ballast water within 30 min under visible light irradiation. The bacterial inactivation rate constant in the coupling system was 26.5 and 6.6 times higher than traditional photocatalysis and Fenton system, respectively, exhibiting 88.8 % of synergistic coupling coefficient. The bactericidal efficiency remained consistent across varying pH levels, allowing direct application of this method in alkaline marine conditions. Free radicals including OH and O2− were proved to be the predominant contributors in the coupling system. The loading of FeOOH QDs could upshift conduction band potential of g-C3N4, thus photogenerated electrons were more easily trapped by O2 to enhance the separation of charge carriers. The photogenerated electrons also accelerated the faster circulation of Fe(III)/Fe(II), which further inhibited electron-hole recombination. Furthermore, bacterial inactivation mechanisms were elucidated by examining total protein changes, intracellular ROSs level and enzyme activities. This work offers innovative approaches for marine bacterial inactivation and ballast water disinfection, which can also find applications in other environmental-related fields.

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.

Biological characteristics of bacteriophage vB_Va_ZX-1 and its therapeutic effect on Chinese mitten crab infected by Vibrio alginolyticus

Intensive aquaculture practices have exacerbated the outbreak of diseases, notably Vibriosis caused by Vibrio alginolyticus (Va). Bacteriophage (Phage) therapy is regarded as a promising alternative to antibiotics. Herein, a Va phage named vB_Va_ZX-1, isolated from the sewage, was shown as a typical morphology of a short-tailed phage by transmission electron microscopy (TEM). The biological characteristics experiment revealed that vB_Va_ZX-1 exhibited a latency period of 15 min, a burst size of 81 PFU/cell, and a broad stability across diverse environments. In addition, genomic bioinformatics analysis revealed that vB_Va_ZX-1 is a novel phage belonging to the genus Kaohsiungvirus within the Autographiviridae family. Its genome consists of a double-stranded DNA spanning 43,533-bp and exhibits a GC content of 43.42%. A total of forty-seven hypothetical open reading frames in vB_Va_ZX-1 genome were predicted, encoding proteins involved in DNA replication, metabolism, packaging, structural components, and host lysis. Notably, no antibiotic resistance genes or virulence factors were detected. Furthermore, in vivo assessment demonstrated that phage treatment protected Chinese mitten crab larvae from Vp24 infection, with a survival rate of up to 90% after 7 days, compared to the rapid mortality of untreated controls within 3 days. Additionally, vB_Va_ZX-1, as a natural bio-antimicrobial agent, significantly reduced the quantity of Vibrio alginolyticus by 90% compared to the control when used as a spray on the surface of salmon slices. In conclusion, vB_Va_ZX-1 holds potential as a novel antimicrobial agent.

Pollution by Agricultural Pesticides and Coliform Bacteria of Two Coastal Ecosystems in Sinaloa, Mexico and a Simple, Economic System for their Reduction

In agricultural valleys of coastal areas of Sinaloa State, Mexico, intensive agriculture has been developed with a high input of agrochemicals, particularly pesticides. This has resulted in an increase of coastal water pollution, which receives discharges from agricultural drains, channels, etc. Consequently, seafood extracted from these water bodies does not guarantee the safety required for human consumption. Therefore, during the dry and rainy seasons, February–June 2022 and July–September 2023 respectively, the amount and type of pesticides and coliform bacteria in water, sediments, as well as in clams and oysters (Anadara spp., Crassostrea, spp.) were evaluated in Altata bay and Ceuta bay, located in central part of Sinaloa, since they receive discharges from the agricultural valleys of Navolato and Culiacán; In addition, some pathogenic bacteria, such as Salmonella Spp., Vibrio ssp., etc., were determined to know the risk of mollusks consumption. Results indicated that pesticide pollution was from moderate to very high. Methoxychlor was the most frequent pesticide found, with values up to 509.607 μg/g-oyster tissue and 39.79 μg/L of water. The fecal coliform values in water ranged from 28 NMP/100 ml in March 2022 to 3609 NMP/100 ml in August 2023, while the total coliforms in mollusks were 136 NMP/g-tissue in clams in March, up to 9600 NMP/g in oysters in September, exceeding the permissible levels established in Mexican normativity. In some bivalve samples, pathogenic bacteria were found, such as Enterobacter agglomerans, Klebsiella pneumoniae, Vibrio alginolyticus, Aeromonas caviae, Listonella anguillarum, Pseudomonas mendocina, Pseudomonas aeruginosa, and Acinetobacter iwoffi. Finally, to reduce the pollutants amount in mollusks, a simple system was implemented, placing the mollusks in aquariums and using a pump (which circulates the aquariums water through filters), and small amounts of chlorine were added as a bactericidal agent. This treatment, by three weeks, decreased between 40% to 70% of the pesticides and coliform bacteria, respectively, improving the safety degree of mollusks and then risk to public health.

Autochthonous probiotic bacteria improve intestinal pathology and histomorphology, expression of immune and growth-related genes and resistance against Vibrio alginolyticus in Asian seabass (Lates calcarifer).

The study isolated two strains of intestinal autochthonous bacteria Lactiplantibacillus plantarum1 (MH155966.1) (L1) and Lactiplantibacillus plantarum2 (MH105076.1) (L2) from the Choobdeh Abadan region. The aim of this study was to investigate the effects of different strains of probiotic bacteria on the growth performance, digestive enzyme activity, histopathologic and histomorphometric characterization of the intestine, expression of immune and growth related genes, and evaluate Lates calcarifer resistance against Vibrio alginolyticus. To achieve this, for each treatment 60 L. calcarifer juveniles (75 ± 12g) were randomly distributed in three fiberglass tanks (300L) and fed for 45 days. The treatments were established as Diet 1 (control diet); L1 (diet with Lb. plantarum isolated 1); L2 (diet with Lb. plantarum isolated 2) with a bacterial concentration of 1 × 109 CFU/g. Nine fish from each treatment were sampled and examined, after euthanasia. The fish were placed 2cm from the beginning of the intestine for microscopic sampling of villi height, villi width and thickness of the epithelium, with 3 treatments: The result showed differences in the mean values of total weight were found at the end of the experiment. After 45 days of culture, the fish fed with L1 had higher (P < 0.05) growth performance than the other treatment groups. But at the end of the trial, in L2, the digestive enzyme activities were higher (P < 0.05) than the other treatment groups. The fishes fed diets supplemented with the L2 group, like the digestive enzyme activities test, presented an increase in the thickness of the epithelium of the intestine, and villus height, and villus width were greatest in L2. Fish feeding with L1 and L2 probiotics induced higher transcription levels of interleukin-10 (IL-10), granulocyte-macrophage colony-forming cells (GMCFC), epidermal growth factor (EGF), and Transforming Growth Factor Beta (TGF-β) genes in the gut, which may correlate with better immune and hematological parameters in these groups. The results of the challenge test revealed that the percentage of survival was significantly higher in L1 (76.2%) and L2 (80.95%) treatments than in the control (P < 0.05). These results indicate that host-derived probiotics (Lb. plantarum) have significant potential as important probiotics to enhance nutrient utilization, Digestive enzymes, and metabolism by increasing the gut surface area of Lates calcarifer juveniles at 45 days of culture.

Energy reserves and gut microbiota of marine mussels under combined exposure to pathogens and predation risk

In recent years, environmental issues such as eutrophication have led to proliferation of pathogenic bacteria and deterioration of aquaculture environmental water quality. However, the impact of pathogenic bacteria on the mussel-predator food chain in the marine environment is not yet fully understood. In this experiment, mussels were cultured with crabs (Charybdis japonica) for 14 days. Then crabs were retained or removed and pathogenic bacteria (Vibrio alginolyticus) was added and mussels were cultured for 3 days. C. japonica and V. alginolyticus were used as two stressors to explore their effects on energy content and gut microbiota of Mytilus coruscus. The metabolic parameters (protein, carbohydrate and lipid contents) of the gills and digestive glands, and the gut microbiota of the mussels were measured. The study found that presence of predation risk significantly increased the content of protein but decreased carbohydrate and lipid contents in the gills at 14th day. After 17 days of exposure, the presence of predation risk significantly reduced protein content but significantly increased lipid content in gills of mussel. The protein content in digestive gland was significantly increased, but the lipid content was significantly decreased. The presence of predation risk and pathogens had interactive effect on the protein content in the digestive glands of mussels. The presence of V. alginolyticus and predation risk affected the community structure, species richness, and diversity of gut microbiota. The most abundant phyla noted were Bacteroidota, Proteobacteria, and Firmicutes, and the most abundant genus noted were Prevotella, Klebsiella and Dialister. Alpha diversity analysis and beta diversity analysis revealed that the presence of V. alginolyticus and predation risk altered the microbial community structure. V. alginolyticus plays a positive role in the harmful microbiota of gut microbiota. The proportion of Bacteroidota and Proteobacteria in intestinal bacteria increased significantly. Linear discriminant analysis effect size (LEfSe) showed that the biomarkers in each group are significantly different at the genus level. Significant correlations between metabolic parameters (protein content and carbohydrate content) and the level of KEGG function prediction (amino acid metabolism and carbohydrate metabolism) were observed in gills and digestive glands. This study highlights the priority of energy responses in mussels under dual predator-pathogen pressure, and also highlights the complexity of predator-pathogen interactions. A better understanding of their impact on the gut microbiota and health of marine mussels will help support the sustainability of mussel aquaculture production.

Otitis by Vibrio Alginolyticus: An Emerging Entity without a Defined Seasonal Pattern: Contaminated Water Exposure or Persistent Colonization?

A significant change in the seasonal patterns of ear infections has been observed due to the modification of aquatic leisure habits, also altering the etiology of the most frequently causing otitis in its various forms of presentation. This work aims to become the largest series documenting ear infections by this bacterium, carrying out a characterization and considering the possibility that the mechanism of action occurs both through contact with contaminated waters and colonization of the middle ear.

Isolation and Characterization of a Novel Vibrio Phage vB_ValA_R15Z.

Vibrio phages have emerged as a potential alternative to antibiotic therapy for treating Vibrio infections. In this study, a lytic Vibrio phage, vB_ValA_R15Z against Vibrio alginolyticus ATCC 17749T, was isolated from an aquatic water sample collected in Xiamen, China. The phage had an icosahedral head (diameter 69 ± 2nm) and a short, non-contractile tail measuring 16 ± 2nm. The genome of vB_ValA_R15Z was found to be a double-stranded DNA consisting of 43, 552bp, containing 54 coding sequences (CDSs) associated with phage packaging, structure, DNA metabolism, lysis and additional functions. The BLASTN results indicated that vB_ValA_R15Z shared less than 90.18% similarity with known phages recorded in the NCBI GenBank database, suggesting that vB_ValA_R15Z was a novel Vibrio phage. Furthermore, phylogenetic analysis revealed that vB_ValA_R15Z belongs to the genus Kaohsiungvirus. In addition, a typical lytic mechanism (holin-endolysim) was found in the genome of vB_ValA_R15Z, while no antibiotic resistance- or virulence factor-related gene was detected. Overall, the study provides valuable insights into the isolation and characterization of vB_ValA_R15Z, highlighting its potential as an effective phage therapy option for combating Vibrio alginolyticus infections.

Characteristics and pathogenicity of Vibrio alginolyticus SWS causing high mortality in mud crab (Scylla serrata) aquaculture in Hong Kong.

Vibrio alginolyticus is a Gram-negative, rod-shaped bacterium belonging to the family of Vibrionaceae, a common pathogen in aquaculture animals, However, studies on its impact on Scylla serrata (mud crabs) are limited. In this study, we isolated V. alginolyticus SWS from dead mud crab during a disease outbreak in a Hong Kong aquaculture farm, which caused up to 70% mortality during summer. Experimental infection and histopathology were used to investigate the pathogenicity of V. alginolyticus SWS in S. serrata and validate Koch's postulates. Comprehensive whole-genome analysis and phylogenetic analysis antimicrobial susceptibility testing, and biochemical characterization were also performed. Our findings showed that V. alginolyticus SWS caused high mortality (75%) in S. serrata with infected individuals exhibiting inactivity, loss of appetite, decolored and darkened hepatopancreas, gills, and opaque muscle in the claw. Histopathological analysis revealed tissue damage and degeneration in the hepatopancreas, gills, and claw muscle suggesting direct and indirect impacts of V. alginolyticus SWS infection. This study provides a comprehensive characterization of V. alginolyticus SWS as an emerging pathogen in S. serrata aquaculture. Our findings underscore the importance of ongoing surveillance, early detection, and the development of targeted disease management strategies to mitigate the economic impact of vibriosis outbreaks in mud crab aquaculture.

Antibacterial activity and virulence attenuation of peptides-zinc nanocomposite against Vibrio alginolyticus

Vibrio alginolyticus (V. alginolyticus) is a common foodborne pathogen that poses a serious threat to food safety, therefore it urgently needs to be effectively controlled. In this study, a novel peptides-zinc nanocomposite (P@ZnNP) with antibacterial activity was fabricated from crimson sapper scales peptides (CSSP). The effect of P@ZnNP on V. alginolyticus was expected from the antibacterial and anti-virulence properties, as well as corresponding mechanism. The minimum inhibitory concentration (MIC) and time-killing curve data showed that P@ZnNP with a concentration of 0.23 mg/mL exhibited significant antibacterial activity against V. alginolyticus. The analysis of the antibacterial mechanism of planktonic V. alginolyticus illustrated that it acted through membrane damage. The virulence related results revealed that the motility, biofilm formation, extracellular polysaccharide production, and alkaline serine protease synthesis of V. alginolyticus were significantly inhibited. Furthermore, in fresh shrimp models, P@ZnNP could reduce bacterial abundance and attenuate virulence. Given these findings, it is believed that P@ZnNP has the potential to become an antibacterial agent against V. alginolyticus in the food industry.

Correction for Gao et al., "Identification of the Regulon of AphB and Its Essential Roles in LuxR and Exotoxin Asp Expression in the Pathogen Vibrio alginolyticus".

Correction for Gao et al., "Identification of the Regulon of AphB and Its Essential Roles in LuxR and Exotoxin Asp Expression in the Pathogen Vibrio alginolyticus".

Prevalence, antibiotic susceptibility, and genomic analysis of Vibrio alginolyticus isolated from seafood and freshwater products in China.

This study characterized Vibrio alginolyticus isolated from seafood and freshwater products in China (2020). In total, 122 (95.31%) V. alginolyticus isolates were resistant to at least 1 antibiotic category, and 2 (1.56%) isolates were resistant to at least 3 antibiotic categories and belong to multi-drug resistance (MDR) isolates. A high prevalence rate was observed to be blaCARB (98.04%) encoding beta-lactam resistance, followed by tet (97.06%) encoding tetracycline resistance and fos (4.90%) encoding resistance to fosfomycin. Among the 57 V. alginolyticus isolates, the commonest virulence genes were type III secretion system translocated gene vopD, vopB, and vcrH (54.4%, 31/57), type III secretion system regulated gene tyeA (54.39%), followed by vscI and vscF (50.88%) encoded type III secretion system inner rod protein and needle protein, respectively. Multilocus sequence typing (MLST) showed considerable genetic diversity, with 34 distinct sequence types (STs) identified among 55 isolates. ST421 (n = 5), ST166 (n = 4), ST523 (n = 3), ST516 (n = 3), and ST507 (n = 3) were dominant STs among 55 V. alginolyticus isolates. These findings highlight the widespread occurrence of V. alginolyticus in both freshwater and seafood products, underscoring the critical need for vigilant monitoring of these bacteria. Such measures are essential for ensuring effective food safety management and safeguarding public health.

Application of Natural Antibacterial Plants in the Extraction of Uranium from Seawater.

Marine biofouling directly affects the performance and efficiency of uranium (U(VI)) extraction from seawater. Compared to traditional chemical methods, natural plant extracts are generally biodegradable and nontoxic, making them an environmentally friendly alternative to synthetic chemicals in solving the marine biofouling problem. The effectiveness of natural antibacterial plants (i.e., pine needle, peppermint, Acorus gramineus Soland, Cacumen platycladi, and wormwood) in solving the marine biofouling problem was evaluated in this work. Experimental results showed that natural antibacterial plants could kill Vibrio alginolyticus in solution and effectively solve the marine biofouling problem of U(VI) extraction. To improve the adsorption capacity of natural plants for U(VI) in seawater, poly(vinylphosphonic acid) (PVPA) was modified on natural antibacterial plant surfaces by irradiation grafting technology. PVPA and natural antibacterial plants work as active sites and base materials for the U(VI) extraction material, respectively. The recovery performance of PVPA/pine needle for U(VI) was preliminarily studied. Results show that the adsorption of U(VI) on PVPA/pine needle follows pseudo-second-order and Langmuir models, and the maximum adsorption capacity is 111 mg/g at 298 K and pH 8.2.

Vibrio alginolyticus PEPCK Mediates Florfenicol Resistance through Lysine Succinylation Modification.

Protein succinylation modification is a common post-translational modification (PTM) that plays an important role in bacterial metabolic regulation. In this study, quantitative analysis was conducted on the succinylated proteome of wild-type and florfenicol-resistant Vibrio alginolyticus to investigate the mechanism of succinylation regulating antibiotic resistance. Bioinformatic analysis showed that the differentially succinylated proteins were mainly enriched in energy metabolism, and it was found that the succinylation level of phosphoenolpyruvate carboxyl kinase (PEPCK) was highly expressed in the florfenicol-resistant strain. Site-directed mutagenesis was used to mutate the lysine (K) at the succinylation site of PEPCK to glutamic acid (E) and arginine (R), respectively, to investigate the function of lysine succinylation of PEPCK in the florfenicol resistance of V. alginolyticus. The detection of site-directed mutagenesis strain viability under florfenicol revealed that the survival rate of the E mutant was significantly higher than that of the R mutant and wild type, indicating that succinylation modification of PEPCK protein may affect the resistance of V. alginolyticus to florfenicol. This study indicates the important role of PEPCK during V. alginolyticus antibiotic-resistance evolution and provides a theoretical basis for the prevention and control of vibriosis and the development of new antibiotics.

Pan-Genome Provides Insights into Vibrio Evolution and Adaptation to Deep-Sea Hydrothermal Vents.

This study delves into the genomic features of 10 Vibrio strains collected from deep-sea hydrothermal vents in the Pacific Ocean, providing insights into their evolutionary history and ecological adaptations. Through sequencing and pan-genome analysis involving 141 Vibrio species, we found that deep-sea strains exhibit larger genomes with unique gene distributions, suggesting adaptation to the vent environment. The phylogenomic reconstruction of the investigated isolates revealed the presence of 2 main clades: The first is monophyletic, consisting exclusively of Vibrio alginolyticus, while the second forms a monophyletic clade comprising both Vibrio antiquarius and Vibrio diabolicus species, which were previously isolated from deep-sea vents. All strains carry virulence and antibiotic resistance genes related to those found in human pathogenic Vibrio species which may play a wider ecological role other than host infection in these environments. In addition, functional genomic analysis identified genes potentially related to deep-sea survival and stress response, alongside candidate genes encoding for novel antimicrobial agents. Ultimately, the pan-genome we generated represents a valuable resource for future studies investigating the taxonomy, evolution, and ecology of Vibrio species.

Morphologic, cytometric, quantitative transcriptomic and functional characterisation provide insights into the haemocyte immune responses of Pacific abalone (Haliotis discus hannai).

In recent years, the abalone aquaculture industry has been threatened by the bacterial pathogens. The immune responses mechanisms underlying the phagocytosis of haemocytes remain unclear in Haliotis discus hannai. It is necessary to investigate the immune mechanism in response to these bacterial pathogens challenges. In this study, the phagocytic activities of haemocytes in H. discus hannai were examined by flow cytometry combined with electron microscopy and transcriptomic analyses. The results of Vibrio parahaemolyticus, Vibrio alginolyticus and Staphylococcus aureu challenge using electron microscopy showed a process during phagosome formation in haemocytes. The phagocytic rate (PP) of S. aureus was higher than the other five foreign particles, which was about 63%. The PP of Vibrio harveyi was about 43%, the PP peak of V. alginolyticus in haemocyte was 63.7% at 1.5h. After V. parahaemolyticus and V. alginolyticus challenge, acid phosphatase, alkaline phosphatase, total superoxide dismutase, lysozyme, total antioxidant capacity, catalase, nitric oxide synthase and glutathione peroxidase activities in haemocytes were measured at different times, differentially expressed genes (DEGs) were identified by quantitative transcriptomic analysis. The identified DEGs after V. parahaemolyticus challenge included haemagglutinin/amebocyte aggregation factor-like, supervillin-like isoform X4, calmodulin-like and kyphoscoliosis peptidase-like; the identified DEGs after V. alginolyticus challenge included interleukin-6 receptor subunit beta-like, protein turtle homolog B-like, rho GTPase-activating protein 6-like isoform X2, leukocyte surface antigen CD53-like, calponin-1-like, calmodulin-like, troponin C, troponin I-like isoform X4, troponin T-like isoform X18, tumor necrosis factor ligand superfamily member 10-like, rho-related protein racA-like and haemagglutinin/amebocyte aggregation factor-like. Some immune-related KEGG pathways were significantly up-regulated or down-regulated after challenge, including thyroid hormone synthesis, Th17 cell differentiation signalling pathway, focal adhesion, melanogenesis, leukocyte transendothelial migration, inflammatory mediator regulation of TRP channels, ras signalling pathway, rap1 signalling pathway. This study is the first step towards understanding the H. discus hannai immune system by adapting several tools to gastropods and providing a first detailed morpho-functional study of their haemocytes.

Bacillus subtilis 2118 exhibits bactericidal activity due to an inserted fish cDNA library

The probiotic Bacillus subtilis represents an efficient, environmentally friendly biocontrol agent to address the problem of evolving, mutation, and dissemination of multidrug-resistant bacteria. In the current study, B. subtilis 2118 strain was screened based on an insert fragment from a large yellow croaker cDNA library damage effect on the B. subtilis host. The supernatant of B. subtilis 2118 displayed a wide-spectrum antibacterial activity against one Gram+ and five Gram- bacteria, including Staphylococcus aureus, Aeromonas hydrophila, A. veronii, Escherichia coli, Vibrio alginolyticus, and V. parahemolyticus. It was further found that B. subtilis 2118 crude protein displayed bactericidal activity against indicator bacteria S. aureus and A. hydrophila with MIC of 187.50 μg/mL and 375.00 μg/mL, and MBC of both 375.00 μg/mL. The mechanism studies indicated that B. subtilis 2118 crude protein was mainly involved in collapse of cell membrane, cytoplasm agglutinating and outflow, and increasing membrane permeability. Besides these, the crude protein has potential of binding bacterial DNA, and probably interfering protein synthesis or degrading protein. Furthermore, B. subtilis 2118 crude protein maintains stable antibacterial activity even when pH 3–11, temperature 25–100 °C, UV radiation 0–60 min, and different proteases handling. In addition, B. subtilis 2118 crude protein has scarce hemolysis and less cytotoxicity towards 293 T and PCK cells. Taken together, B. subtilis 2118 strain and its crude protein have strong potential as alternative agents for antibiotics in aquaculture.

Technical specifications for a EU-wide baseline survey of antimicrobial resistance in bacteria from aquaculture animals.

The European Commission requested scientific and technical assistance in the preparation of a EU-wide baseline survey of antimicrobial resistance (AMR) in bacteria from aquaculture animals. It is recommended that the survey would aim at estimating the occurrence of AMR in Aeromonas spp. isolated from Atlantic Salmon (Salmo salar), European seabass (Dicentrarchus labrax) and trout (Salmo trutta, Salvelinus fontinalis, Oncorhynchus mykiss) intended to consumption, at harvesting (at farm/slaughter), at the EU level and in addition, at estimating the occurrence and diversity of AMR of Escherichia coli, Enterococcus faecium, Enterococcus faecalis, Vibrio parahaemolyticus and Vibrio alginolyticus in blue mussel (Mytilus edulis) and Mediterranean mussel (Mytilus galloprovincialis) from production areas and at dispatch centres at the EU level. These technical specifications define the target populations, the sample size for the survey, sample collection requirements, the analytical methods (for isolation, identification, phenotypic susceptibility testing and further genotypic analysis of some of the bacteria targeted) and the data reporting requirements. The data to be reported by the EU Member States to support this baseline survey are presented in three data models. The results of the survey should be reported using the EFSA reporting system.