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Simple Summary: This study investigates the set of proteins that comprise a Vibrio ordalii strain Vo-LM-18 and its outer membrane vesicles (OMVs), which are involved in the pathogen's interaction with fish hosts, especially salmonids. Vibrio ordalii is a major cause of vibriosis, a disease that results in significant mortality in fish farms, a relevant industry in Chile. By analyzing the proteins expressed by both the bacteria and their OMVs, this research identifies key proteins linked to virulence, iron uptake, and cellular communication. The findings suggest that OMVs carry virulence factors that could aid in the pathogen's ability to infect and persist in fish. These vesicles may also contribute to the pathogen's survival in harsh environments, such as during host immune responses. This study provides new insights into bacterial pathogenesis and highlights potential targets for developing treatments or vaccines to combat infections in aquaculture. Vibrio ordalii is the causative agent of atypical vibriosis in salmonids cultured in Chile. While extensive research provides insights into V. ordalii through phenotypic, antigenic, and genetic typing, as well as various virulence mechanisms, proteomic characterization remains largely unexplored. This study aimed to advance the proteomic knowledge of Chilean V. ordalii Vo-LM-18 and its OMVs, which have known virulence. Using Nano-UHPLC-LC-MS/MS, we identified 2242 proteins and 1755 proteins in its OMVs. Of these, 644 unique proteins were detected in V. ordalii Vo-LM-18, namely 156 unique proteins in its OMVs and 1596 shared proteins. The major categories for the OMVs were like those in the bacteria (i.e., cytoplasmic and cytoplasmic membrane proteins). Functional annotation identified 37 biological pathways in V. ordalii Vo-LM-18 and 28 in its OMVs. Proteins associated with transport, transcription, and virulence were predominant in both. Evident differences in protein expression were found. OMVs expressed a higher number of virulence-associated proteins, including those related to iron- and heme-uptake mechanisms. Notable pathways in the bacteria included flagellum assembly, heme group-associated proteins, and protein biosynthesis. This proteomic analysis is the first to detect the RTX toxin in a V. ordalii strain (Vo-LM-18) and its vesicles. Our results highlight the crucial role of OMVs in the pathogenesis and adaptation of V. ordalii, suggesting use as potential diagnostic biomarkers and therapeutic targets for bacterial infections. [ABSTRACT FROM AUTHOR]

This paper explores how Chesapeake-based watermen and seafood processors may experience occupational harm from microbial hazards like Vibrio spp. Fishing industry research primarily focuses on musculoskeletal injury, even though microbial hazards present risks to Total Worker Health® that clinicians should consider. This paper provides qualitative insights to address that gap. Commercial fishing is a dangerous profession with known hazards for musculoskeletal injuries, yet minimal examination of microbiological or attendant psychosocial hazards from water- and food-borne pathogens like Vibrio vulnificus and V. parahaemolyticus exists. Improving knowledge of Vibrio -related hazards addresses Total Worker Health® concerns for commercial fisheries workers. Methods: Following a grounded theory approach, we conducted semistructured interviews with watermen and related workers who fish and harvest shellfish in the Chesapeake Bay, USA, to investigate risk perceptions and understanding, and compliance with regulations intended to reduce worker and consumer illnesses and injuries from pathogen exposures. Results: Worker and consumer illnesses and injuries, and threat of fishery closures—with regulatory and organizational factors—influence this workforce. Conclusions: Our findings support interventions that promote monitoring, surveillance, and awareness of Vibrio- related risk among watermen, regulatory officials, medical professionals, and the public. [ABSTRACT FROM AUTHOR]

For more than a century, bacterial infections caused by Vibrio spp. have affected various species of mussels around the world, with limited insights into the responses implemented by mussels against these infections. A combination of chemical analyses and carefully selected biological endpoints from haemolymph and tissues can be used to identify the welfare status of mussels and potentially protect aquatic ecosystems from catastrophic health threats. Recent developments in biomarker identification tools, such as omics and bioinformatics, have been successfully applied to evaluate the effect of environmental pollutants and other chemicals on mussels. However, the application of biomarkers to assess mussel health is limited. This review describes the available scientific literature on biomarker research for Vibrio-mussel interactions, and those aspects related to mussel health and disease assessment, grouped as biomarkers of exposure, effects, and susceptibility. From the review, it is clear that when integrated biomarkers are used, they can provide a deeper understanding of the relative health and potential susceptibility of mussels for better management practices. Furthermore, health biomarker data can be used to build resilience in mussels against climate change conditions, strengthen biosecurity management programs, improve farming and processing efficiency, and add value in terms of market-desirable traits. These data hold promise for advancing sustainability efforts within the aquaculture industry. [ABSTRACT FROM AUTHOR]

Abstract Vibrio parahaemolyticus is pathogenic to both humans and marine animals. Antimicrobial-resistant (AMR) bacteria have been reported to cause mortalities in shrimp, with phage therapy presenting an alternative and eco-friendly biocontrol strategy for controlling bacterial diseases. Therefore, this study aimed to isolate and characterize phages for their applicability in lysing Vibrio parahaemolyticus. A novel phage vB_VpaS_BP15 (BP15) belonged to the subfamily Queuovirinae with an icosahedral head measuring 69.11 ± 5.38 nm in length and 65.40 ± 6.89 nm in width, and a non-contractile sheathed tail measuring 139.81 ± 14.79 nm. The one-step growth curve indicated a latent period of 30 min and a burst size of 120 PFUs per cell. Phage BP15 exhibited tolerance to a range of temperatures and pH values. Infection dynamic curves demonstrated that BP15 was highly effective against BCRC12959 at MOIs ranging from 0.01 to 10; even at a low multiplicity of infection (MOI) of 0.001, BP15 still caused growth retention. Phage BP15 possessed a circular double-stranded DNA of 59,584 bp with a G + C content of 46.7% and lacked tRNA genes, virulence genes, and lysogeny genes. These findings highlight the promising potential of phage BP15 as a biocontrol agent against Vibrio parahaemolyticus in Taiwan.

Graphical Abstract Highlight Research • The LD50 (median lethal dose) of Vibrio parahaemolyticus and harveyi in zebrafish was determined to be 1 x 106 CFU/mL, while for V. alginolyticus it was found to be 1 x 105 CFU/mL. • The LAVh vaccine demonstrated cross-protection against various pathogenic strains of Vibrio, leading to an average of 80% survival rate in vaccinated individuals. • The analysis of the LAVh vaccine emphasized its versatility, as it can be quickly deployed and stored as a freeze-dried powder. • The LAVh vaccine can be easily accessible and user-friendly in various aquaculture environments, such as offshore and remote farms. Abstract Vibriosis poses a significant threat to marine teleosts, causing substantial losses in the global aquaculture industry. Previous work in our lab led to the development of a live-attenuated V. harveyi vaccine (LAVh) candidate that targets the serine endoprotease gene with a three-point knockout and has shown promise in protecting against vibriosis. However, further investigation is necessary to evaluate the stability and efficacy of its various storage conditions for broader applications. This study aims to determine how well the three different LAVh vaccine storage (fresh, stale, and freeze-dried LAVh) worked against vibriosis. A total of 1000 adult zebrafish (Danio rerio) (mean weight: 0.20±0.5 g) were divided into four groups. Groups 1, 2, and 3 were intraperitoneally injected with different LAVh vaccine storage (fresh, stale, and freeze-dried, respectively), while Group 4 received 0.01 M phosphate-buffered saline (PBS) and served as the unvaccinated control. Fish were monitored for 21 days post-vaccination for safety, stability, efficacy, and antibody analysis. The results showed that a modest dosage of 1 x 104 CFU/mL of LAVh vaccine from all storage conditions provided 80% survival upon intraperitoneal challenge with pathogenic strains of pathogenic V. harveyi, V. alginolyticus, and V. parahaemolyticus. This dosage induced significant antibody production and conferred cross-protection against different Vibrio spp., indicating the LAVh vaccine’s potential for commercial application. The LAVh vaccine demonstrated high effectiveness and suitability for storage as a freeze-dried powder. This study might offer significant insights into practical strategies for reducing vibriosis, especially in aquaculture settings with limited infrastructure.

ABSTRACT Studies on preventing antimicrobial resistance in aquaculture emphasise the need to responsibly and prudently use antimicrobials, selecting those most effective in controlling and/or reducing mortalities caused by vibriosis. In this study, the distribution of the antimicrobial susceptibility of 28 Vibrio anguillarum isolates from Turkish fish farms was determined using the broth microdilution minimum inhibitory concentration (MIC) test according to the Clinical and Laboratory Standards Institute (CLSI) guideline. The epidemiological cut‐off (COWT) values of the V. anguillarum isolates of florfenicol (FLO), tetracycline (TET), doxycycline (DOX), oxolinic acid (OXO), enrofloxacin (ENR) and trimethoprim/sulfamethoxazole (SXT) were calculated using the normalised resistance interpretation (NRI) and ECOFFinder methods. Isolates were categorised as belonging to the fully susceptible wild‐type (WT) or non‐wild‐type (NWT) populations. Calculated COWT values (in μg mL−1) were ≤ 1.0 for FLO and DOX, ≤ 0.5 for TET, ≤ 0.016 for ENR, ≤ 0.032 for OXO, and ≤ 4.0 for SXT using the NRI analysis. Percentages of V. anguillarum isolates categorised as belonging to the NWT population were small for the antimicrobials FLO (10.7%) and SXT (0%), whereas they were higher for the antimicrobials OXO (39.3%) and ENR (39.3%). This is the first study to estimate the local COWT values for antibiotics used in the control of V. anguillarum isolates recovered from farmed fish in Turkey. [ABSTRACT FROM AUTHOR]

Immunosaccharides such as β-glucans and fructooligosaccharide (FOS) strengthen the host's immune responses. This study examined the influences of three levels of the β-1, 3 glucan-FOS combination on Red tilapia performance. Four diets were prepared: T0 as a control, while T0.5, T1, and T1.5 indicate the addition of β-1, 3 glucan-FOS mixture at 0.5%, 1%, and 1.5%, respectively. Then, 240 red Tilapia (Oreochromis niloticus x O. mossambicus) (weight 6.1 ± 0.07gm) were allocated into four groups, and every group was fed tested diets for 56 days. After the feeding trial, growth parameters, erythrogram profile, liver and kidney function testes, glucose, histopathological analysis, and gene expressions for antioxidants, catalase (CAT) and glutathione peroxidase (GPX) besides growth hormone (GH) and insulin-like growth factor 1 IGF1-related markers were assessed. Red tilapia fed T0.5, T1, and T1.5 exhibited consistent growth, survival rate, and homeostasis compared with the control group. Different supplement concentrations displayed varying levels of responses. The hepatorenal biomarkers (alanine transaminase (ALT = SGPT) and aspartate transaminase (AST = SGOT), alkaline phosphatase (ALP = ALK), urea, and creatinine) and glucose showed a significant reduction in the supplemented groups compared with the control, especially in the T1 and T1.5 groups. The intestinal morphometric study revealed that fish group fed on T1 represented the best result, whereas group T1.5, followed by group T0.5, was moderately treated, compared to the control. The real-time quantitative reverse transcription PCR (qRT-PCR) analysis displayed up-regulated expression of antioxidant and growth-correlated genes in the T1.5 groups. After 56 days, the β-1,3 glucan-FOS fed groups also exhibited an increase in survival rates compared to the control when challenged with a pathogenic Vibrio alginolyticus. Current findings suggest that inclusion of β-1,3 glucan-FOS in diets could enhance red tilapia biochemical parameters, growth, and protection against pathogenic V. alginolyticus infection. [ABSTRACT FROM AUTHOR]

Vibrio vulnificus (Vv) is a bacterial pathogen native to warm and brackish water ecosystems that can cause fatal septicemia (Vv-vibriosis) in humans and various farmed fish species. From a One Health perspective, controlling Vv-vibriosis outbreaks on farms is essential not only for animal but also for human health, as it reduces the risk of Vv transmission to humans. Electrolyzed water (EW) is a sustainable control method, exhibiting transient disinfectant properties due to the formation of hypochlorous acid (HOCl). We hypothesized that EW could effectively reduce Vv populations in aquaculture facilities, preventing outbreak emergence. To test this hypothesis, survival assays in EW were conducted under varying conditions of salinity, pH, and free available chlorine (FAC). The results indicated that an intermediate concentration of FAC had a significant bactericidal effect on Vv populations regardless of the condition and tested strain. Consequently, the strategic use of EW could serve as an eco-friendly preventive and control measure against Vv-vibriosis by significantly decreasing the bacterial load in farm water. [ABSTRACT FROM AUTHOR]

Aim Dermaseptins are one of the main families of antimicrobial peptides (AMPs) derived from the skin secretions of Hylidae frogs. Among them, dermaseptin S4 (DS4) is characterized by its broad-spectrum of activity against bacteria, protozoa, and fungi. In this study, the physicochemical properties of the native peptide DS4 (1–28) and two derivatives [DS4 (1–28)a and DS4 (1–26)a] isolated from the skin of the frog Phyllomedusa sauvagii were investigated and their antimicrobial properties against two marine pathogenic bacteria (Vibrio harveyi and Vibrio anguillarum) were examined. Methods and results The results indicate that the peptide DS4 (1–26)a has high-antibacterial activity against the tested strains and low-hemolytic activity (<30% lysis at the highest tested concentration of 100 µg/mL) compared to the other two peptides tested. In addition, all three peptides affect the membrane and cell wall integrity of both pathogenic bacteria, causing leakage of cell contents, with DS4 (1–26)a having the most severe impact. These skills were corroborated by transmission electron microscopy and by the variation of cations in their binding sites due to the effects caused by the AMPs. Conclusions These results suggest that DS4 and its derivatives, in particular the truncated and amidated peptide DS4 (1–26)a could be effective in the treatment of infections caused by these marine pathogenic bacteria. Future studies are required to validate the use of DS4 in vivo for the prevention of bacterial diseases in fish. [ABSTRACT FROM AUTHOR]

Microalgae Chlorella is widely used as immune-enhancer in aquaculture. To investigate the immunoregulatory mechanisms induced by Chlorella pyrenoidosa, the short-term (15 days) and long-term (60 days) immunostimulatory effects of C. pyrenoidosa on hybrid groupers (E. lanceolatus × E. fuscoguttatus) were examined, revealing that juveniles reared in Chlorella monoculture rearing water (CMW) display better survival upon pathogenic Vibrio harveyii challenge than those otherwise. The findings showed reduced free radical activity and higher antioxidant capacity in fish reared short-term and long-term in CMW. The innate immunity was robustly enhanced in short-term CMW rearing, with more mucus cells covering the gill secondary lamellae and the formation of more melano-macrophage centers (MMCs) in the spleen. CMW mitigated organ damage in V. harveyi challenged fish in both short- and long-term trials, but a higher survival was only observed in fish reared short-term in CMW. Transcriptomic analysis revealed that short-term rearing in CMW regulated the expression of innate immune (IRF4, IL-11, IL12RB2, CK3), anti-inflammatory (SELE, PTGIS, HMOX), apoptosis-inhibitory (NR4A1, NR4A3, CTRP3, BCL3), and proteolytic (UBB, HSP70, HSP90, KDM6B, SCARB2) genes. Elevated oxidative phosphorylation-related gene expressions were stimulated, possibly due to the high metabolic commitment of immune system regulation. The findings extend the understanding and provide valuable insights on the immuno-enhancing properties of CMW. The application of CMW would potentially improve marine larviculture performance.

Lumpfish (Cyclopterus lumpus) have become the predominant cleaner fish species used in North American salmon aquaculture. Vibrio anguillarum is a frequent pathogen of lumpfish in Atlantic Canada, and current vaccines against local isolates conferred low to moderate efficacy. This study evaluated the safety and efficiency of a V. anguillarum autogenous vaccine under controlled and field conditions. Two safety trials were conducted following the Canadian Food Inspection Agency (CFIA) regulations before field trial testing. The first safety trial was a common garden assay, and 250 PIT-tsgged lumpfish were used for five treatments per tank (PBS-negative control, Lab vaccine-positive control, autogenous intraperitoneal (IP) vaccine, autogenous dip vaccine, autogenous dip-IP boosted vaccine) in triplicates. Weight, gross pathology, and IgM titers were evaluated to determine the vaccine's safety. After 10 weeks postvaccination (wpv), lumpfish were bath-challenged with a lethal dose (1.24 x 106 CFU/mL) of V. anguillarum serotype O2. Survival rate, IgM titers, memory immune response, and cross-immune protection were evaluated. The second safety trial was conducted using a double vaccine dose in two groups, PBS and autogenous IP. The gross pathology score indicated a normal immune response without tissue damage, and no mortality nor fish health issues were observed in the immunized animals. The IP route of administration conferred the highest protection against the V. anguillarum challenge. The autogenous vaccine conferred long-term immunity but did not confer cross-protection against V. anguillarum serotype O1. To evaluate the efficiency of the autogenous vaccine under field conditions, 58,976 naïve lumpfish (8-10 g) were IP immunized with either the autogenous vaccine or the commercial Forte micro IV vaccine. After 7 wpv, the lumpfish were equally distributed into eight sea cages and co-cultivated with Atlantic salmon smolts (60,000 per cage). Lumpfish IgM titers, tissue bacterial loads, mortality, and sea lice count on salmon were monitored. The autogenous vaccine and Forte vaccine confer acceptable protection to the lumpfish in sea cages. No significant difference was observed between lumpfish vaccinated with autogenous and commercial vaccines under field conditions. [ABSTRACT FROM AUTHOR]

Vibrio alginolyticus is the causative agent of vibriosis, a common bacterial infection in grouper aquaculture that is associated with the development of haemorrhagic and non‐haemorrhagic ulcerations on the fish. In the present study, comparative proteome analysis was performed on serum samples from Vibrio‐resistant and Vibrio‐susceptible grouper. Samples were analysed using high‐throughput LC‐MS/MS and identified 2770 unique peptides that corresponded to 344 proteins. Subsequent analysis identified 21 proteins that were significantly up‐regulated in the resistant group compared to the control and the susceptible groups. Those proteins are associated with immunostimulatory effects, signalling and binding cascade, metabolism, and maintaining tissue integrity and physiological condition. Besides, potential protein biomarkers related to the immune system were identified, which could be associated with the disease‐resistant phenotype. These data provide insights into the underlying immune mechanism of hybrid groupers upon Vibrio sp. infection. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the effects of black seed (Nigella sativa) and AQUA-IMMUNOPROTECT® on growth, feed utilization, serum constituents, and disease resistance against vibriosis in gilthead sea bream juveniles. The research involved three groups: TC (control) received a basal diet, TSI (received a basal diet with 2% AQUA-IMMUNOPROTECT®), and TNS (received a basal diet with 2% N. sativa). The experiment period extended for 2 months. Results revealed a significant rise in erythrogram (RBCs, HB, and PCV %), leucogram (total differential leucocytic count), serum total protein, and globulin in gilthead sea bream treated with 2% Nigella sativa supplemented diets after an 8-week trial. No substantial variations were found in liver enzymes, urea, uric acid, and creatinine between the groups. Respiratory burst activity was notably greater in the N. sativa group after 2 months of feeding compared to the other groups. In the experimental challenge, the control group experienced higher mortality rates than the other groups following an IP injection of V. harveyi at a dose of 106 CFU per 0.5 ml/fish (106 fish/challenge). Overall, the findings of this research indicate that N. sativa can enhance non-specific immunity and minimize susceptibility and pathogenicity to V. harveyi in gilthead sea bream. [ABSTRACT FROM AUTHOR]

Nowadays, European seabass (Dicentrarchus labrax) aquaculture is undergoing a significant expansion. Nevertheless, the aquaculture industry is plagued by vibriosis. The spatial and temporal dynamics of Vibrio harveyi were studied on a European seabass farm in northern France during seven months of 2022. Concrete specimens were suspended and water was pumped from different depths (0.3 m, 2.15 m and 4 m deep), providing insights into the biofilm and planktonic V. harveyi dynamics. The abundances of V. harveyi, in the biofilm and free-living forms, were positively correlated. The water parameters revealed seasonal fluctuations in temperature, pH, and salinity, with no significant differences observed across the water column. Quantification of V. harveyi revealed no significant differences between depths, but seasonality, with peak abundances observed in August, correlated with temperature increases. Principal component analysis identified temperature as a primary driver, but also additional parameters, such as salinity and pH. Vibriosis occurred during the sampling period, providing valuable insights into the conditions before, during, and after the outbreaks. This study underscores the importance of understanding V. harveyi behaviour in aquaculture, particularly in the context of global warming, for effective disease management and sustainable practices. [ABSTRACT FROM AUTHOR]

Mass fish kills are abrupt events in which a significant number of fish of different ages and species perish in a specific aquatic region. Dramatic waves of mass kills have involved a large variety of economic fish species in both Egyptian fisheries and the aquaculture sector. Several episodes of mass mortalities of various infectious and noninfectious aetiologies have targeted a wide spectrum of freshwater and marine fish in both open-water and captive environments. Kafr El-Sheikh, Sharkia, Dakahlia, Fayoum, Alexandria and Giza were the most affected Egyptian provinces. The Mediterranean basin, Lake Manzala, Lake Mariott, Lake Burullus, River Nile, and some provincial water streams and municipal water drains were all reported to have had one or more episodes of mass kills over the past two decades. These mass kills were mainly attributed to different types / magnitudes of aquatic environmental pollution, which was explicitly aggravated by poor aquaculture / fishing practices. Further, the frequent absence of veterinary guidance has had a great negative impact on providing possible solutions for this disaster in the near future. Ultimately, adopting Good Aquaculture Practice (GAP), competent biosecurity strategies, and regular veterinary supervision will be the most practical solutions that ensure the reliable growth and sustainability of both Egyptian fisheries and aquaculture sectors.

Abstract Vibrio parahaemolyticus is a gram-negative facultative anaerobic bacterium implicated as the causative agent of several shrimp diseases. As part of the effort to provide biocontrol and cost-effective treatments, this research was designed to elucidate the effect of Morinda citrifolia fruit extract on the immunity of Penaeus vannamei postlarvae (PL) to V. parahaemolyticus. The methanol extract of M. citrifolia was vacuum evaporated, and the bioactive compounds were detected using gas chromatography‒mass spectrometry (GC‒MS). Thereafter, P. vannamei PL diets were supplemented with M. citrifolia at different concentrations (0, 10, 20, 30, 40, and 50 mg/g) and administered for 30 days before 24 h of exposure to the bacterium V. parahaemolyticus. A total of 45 bioactive compounds were detected in the methanol extract of M. citrifolia, with cyclononasiloxane and octadecamethyl being the most abundant. The survival of P. vannamei PLs fed the extract supplement was better than that of the control group (7.1–26.7% survival greater than that of the control group) following V. parahaemolyticus infection. Shrimp fed 50 mg/g M. citrifolia had the highest recorded survival. The activities of digestive and antioxidant enzymes as well as hepatopancreatic cells were significantly reduced, except for those of lipase and hepatopancreatic E-cells, which increased following challenge with V. parahaemolyticus. Histological assessment of the hepatopancreas cells revealed reduced cell degeneration following the administration of the plant extracts (expecially those fed 50 mg/g M. citrifolia) compared to that in the control group. Therefore, the enhanced immunity against V. parahaemolyticus infection in P. vannamei could be associated with the improved hepatopancreas health associated with M. citrifolia fruit extract supplementation.

Abstract Background In this study, the protective immunity and immunogenicity of the monovalent and bivalent Streptococcus iniae and Vibrio harveyi vaccine were evaluated in Asian seabass. To analyze immune responses, 1200 Asian seabass with an average weight of 132.6 ± 25.4 g were divided into eight treatments in triplicates (50 fish per tank) as follows: S. iniae immunized by injection (SI), V. harveyi immunized by injection (VI), bivalent S. iniae and V. harveyi (SVI) immunized by injection, S. iniae immunized by immersion (SIM), V. harveyi (VIM) immunized by immersion, bivalent S. iniae and V. harvei (SVIM) immunized by immersion, phosphate-buffered saline (PBS) by injection (PBSI) and control group without vaccine administration (CTRL). Blood and serum samples were taken at the end of the 30th and 60th days. Then the vaccinated groups were challenged with two bacteria (S. iniae) and (V. harveyi) separately and mortality was recorded for 14 days. Results This study reveals that there is no significant difference in the hematological parameters on the 30th and 60th days of the experiment in the vaccine-immunized groups compared to the CTRL group (P > 0.05). Meanwhile, there was no significant difference in the amount of serum albumin level, respiratory burst activity, and serum bactericidal activity in the vaccine-immunized groups compared to the CTRL group on the 30th and 60th days of the experiment (P > 0.05). Total protein on the 60th day (in the VI and SVI groups), globulin on the 30th day (in the VI and SVI groups) and the 60th day (in the VI group) compared to the CTRL and PBSI groups had a significant increase (P

Background: Vibrio parahaemolyticus is a pathogenic bacterium that affects shrimp aquaculture; its infection can lead to severe production losses of up to 90%. On the other hand, plant phenolic compounds have emerged as a promising alternative to combat bacterial infections. The antibacterial and anti-virulence activity of the plant phenolic compounds quercetin, morin, vanillic acid, and protocatechuic acid against two strains of V. parahaemolyticus (Vp124 and Vp320) was evaluated. Methods: The broth microdilution test was carried out to determine phenolic compounds' antibacterial activity. Moreover, the biofilm-forming ability of V. parahaemolyticus strains in the presence of phenolic compounds was determined by total biomass staining assay using the cationic dye crystal violet. The semisolid agar displacement technique was used to observe the effect of phenolic compounds on the swimming-like motility of V. parahaemolyticus. Results: Results showed that phenolic compounds inhibited both strains effectively, with minimum inhibitory concentrations (MICs) ranging from 0.8 to 35.03 mM. Furthermore, at 0.125 – 0.5 × MIC of phenolic compounds, V. parahaemolyticus biofilms biomass was reduced by 63.22 – 92.68%. Also, quercetin and morin inhibited the motility of both strains by 15.86 – 23.64% (Vp124) and 24.28 – 40.71% (Vp320). Conclusions: The results suggest that quercetin, morin, vanillic, and protocatechuic acids may be potential agents for controlling V. parahaemolyticus.

Vibrio alginolyticus and Streptococcus agalactiae are important bacterial pathogens that yielded high losses in Nile tilapia in Egypt. The present study aimed to check the protective efficacy of inactivated whole-cell bivalent vaccines against these pathogens using incomplete Freund's adjuvant and Montanide™ IMS 1312 VG as adjuvants. The antibody titers have been determined at different weeks post-vaccination (WPV). Moreover, the protection levels against the challenged bacterial pathogens have also been examined in relation to the time-dependent protection at different WPV. The results revealed that serum antibodies were generated in all immunized fish at 1st WPV, peaked at 4th WPV, continued, and gradually decreased from 6th WPV to 14th WPV in all vaccinated groups. In addition, vaccines induced significantly higher protection of the immunized tilapia, manifested by higher survival rates. We noticed that the antibody levels and survival rates of the vaccinated fish by a vaccine adjuvanted by Montanide™ IMS 1312 VG were higher than those produced by a vaccine adjuvanted by incomplete Freund's adjuvant at different time points. Moreover, no external clinical signs, visceral adhesions, or internal lesions were recorded in the vaccinated tilapia, demonstrating the safety of the formulated vaccines. According to the aforementioned findings, we could suggest that the prepared bivalent vaccines, using the two adjuvant types, are safe and highly protective and could be utilized as promising candidate vaccines to increase the resistance of Nile tilapia against V. alginolyticus and S. agalactiae infections. Moreover, Montanide™ IMS 1312 VG enhanced the immuno-protectivity and exhibited optimum immune response and earlier protection compared to the vaccine adjuvanted by incomplete Freund's adjuvant, demonstrating its added value during the preparation of tilapia vaccines. [ABSTRACT FROM AUTHOR]

Canarium indicum offers the potential of usage in aquaculture. This study aimed to evaluate the utilization of C. indicum on growth performance, health, and resistance of Asian seabass Lates calcalifer challenged with Vibrio alginolyticus. The study employed a completely randomized design with seven treatments, namely positive control (K+), negative control (K-), vitamin control (KVit), antibiotic control (KAnt), doses of 5 g kg-1 (D05), 10 g kg-1 (D10), and 20 g kg-1 C. indicum (D20). The test feed was prepared with a coating method and fed for 30 days. On the 31st day of rearing, a challenge test was conducted by injecting V. alginolyticus intramuscularly at 106 CFU mL-1. The results showed that C. indicum treatment for 30 days had a significantly different effect (P<0.05) on weight gain and average daily growth, while KVit and KAnt treatments were not different from the control. After the challenge test, all doses of C. indicum treatment, as well as KVit and KAnt treatments, showed survival significantly different (P<0.05) from that of the positive control, which ranged from 88.89% to 95.56% and was not significantly different (P>0.05) from the negative control. The survival rate condition is identical to the cumulative survival condition which shows the highest mortality found in the positive control. The administration of C. indicum at a dose of 5 g kg-1 to 20 g kg-1 improved the growth performance and prevented V. alginolyticus infection. [ABSTRACT FROM AUTHOR]

Mass fish kills are abrupt events in which a significant number of fish of different ages and species perish in a specific aquatic region. Dramatic waves of mass kills have involved a large variety of economic fish species in both Egyptian fisheries and the aquaculture sector. Several episodes of mass mortalities of various infectious and noninfectious aetiologies have targeted a wide spectrum of freshwater and marine fish in both open-water and captive environments. Kafr El- Sheikh, Sharkia, Dakahlia, Fayoum, Alexandria and Giza were the most affected Egyptian provinces. The Mediterranean basin, Lake Manzala, Lake Mariott, Lake Burullus, River Nile, and some provincial water streams and municipal water drains were all reported to have had one or more episodes of mass kills over the past two decades. These mass kills were mainly attributed to different types / magnitudes of aquatic environmental pollution, which was explicitly aggravated by poor aquaculture / fishing practices. Further, the frequent absence of veterinary guidance has had a great negative impact on providing possible solutions for this disaster in the near future. Ultimately, adopting Good Aquaculture Practice (GAP), competent biosecurity strategies, and regular veterinary supervision will be the most practical solutions that ensure the reliable growth and sustainability of both Egyptian fisheries and aquaculture sectors. [ABSTRACT FROM AUTHOR]

Background: In this study, the protective immunity and immunogenicity of the monovalent and bivalent Streptococcus iniae and Vibrio harveyi vaccine were evaluated in Asian seabass. To analyze immune responses, 1200 Asian seabass with an average weight of 132.6 ± 25.4 g were divided into eight treatments in triplicates (50 fish per tank) as follows: S. iniae immunized by injection (SI), V. harveyi immunized by injection (VI), bivalent S. iniae and V. harveyi (SVI) immunized by injection, S. iniae immunized by immersion (SIM), V. harveyi (VIM) immunized by immersion, bivalent S. iniae and V. harvei (SVIM) immunized by immersion, phosphate-buffered saline (PBS) by injection (PBSI) and control group without vaccine administration (CTRL). Blood and serum samples were taken at the end of the 30th and 60th days. Then the vaccinated groups were challenged with two bacteria (S. iniae) and (V. harveyi) separately and mortality was recorded for 14 days. Results: This study reveals that there is no significant difference in the hematological parameters on the 30th and 60th days of the experiment in the vaccine-immunized groups compared to the CTRL group (P > 0.05). Meanwhile, there was no significant difference in the amount of serum albumin level, respiratory burst activity, and serum bactericidal activity in the vaccine-immunized groups compared to the CTRL group on the 30th and 60th days of the experiment (P > 0.05). Total protein on the 60th day (in the VI and SVI groups), globulin on the 30th day (in the VI and SVI groups) and the 60th day (in the VI group) compared to the CTRL and PBSI groups had a significant increase (P < 0.05). Complement activity (in the VI and SVI groups) and lysozyme (in the SI and SVI groups) increased significantly compared to the control group (P < 0.05). Serum antibody titer against S. iniae had a significant increase in the SI, VI, SVI and SVIM groups compared to the CTRL and PBSI groups (P < 0.05). Serum antibody titer against V. harveyi had a significant increase in the groups immunized with the vaccine compared to the CTRL and PBSI groups (P < 0.05). A significant increase in the relative percentage survival (RPS) following challenge with S. iniae in the SVI (86.6%), SI (83.3%,) and VI (73.3%) groups were observed compared to the CTRL (43.3%) and PBSI (40%) groups (P < 0.05). Also, a significant increase in the RPS after challenge with V. harveyi in the SVI group, VI 86.6%, SVI 83.3%, VIM 80% and SVIM 76.6% were observed compared to the CTRL (46.6%) and PBSI (50%) groups (P < 0.05). Conclusion: Overall, the results demonstrated that the bivalent vaccine of S. iniae and V. harveywas able to produce significant immunogenicity and RPS in Asian seabass [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus is a gram-negative facultative anaerobic bacterium implicated as the causative agent of several shrimp diseases. As part of the effort to provide biocontrol and cost-effective treatments, this research was designed to elucidate the effect of Morinda citrifolia fruit extract on the immunity of Penaeus vannamei postlarvae (PL) to V. parahaemolyticus. The methanol extract of M. citrifolia was vacuum evaporated, and the bioactive compounds were detected using gas chromatography‒mass spectrometry (GC‒MS). Thereafter, P. vannamei PL diets were supplemented with M. citrifolia at different concentrations (0, 10, 20, 30, 40, and 50 mg/g) and administered for 30 days before 24 h of exposure to the bacterium V. parahaemolyticus. A total of 45 bioactive compounds were detected in the methanol extract of M. citrifolia, with cyclononasiloxane and octadecamethyl being the most abundant. The survival of P. vannamei PLs fed the extract supplement was better than that of the control group (7.1–26.7% survival greater than that of the control group) following V. parahaemolyticus infection. Shrimp fed 50 mg/g M. citrifolia had the highest recorded survival. The activities of digestive and antioxidant enzymes as well as hepatopancreatic cells were significantly reduced, except for those of lipase and hepatopancreatic E-cells, which increased following challenge with V. parahaemolyticus. Histological assessment of the hepatopancreas cells revealed reduced cell degeneration following the administration of the plant extracts (expecially those fed 50 mg/g M. citrifolia) compared to that in the control group. Therefore, the enhanced immunity against V. parahaemolyticus infection in P. vannamei could be associated with the improved hepatopancreas health associated with M. citrifolia fruit extract supplementation. [ABSTRACT FROM AUTHOR]

Bovine genital campylobacteriosis, caused by the gram-negative bacteria Campylobacter fetus venerealis, and bovine trichomonosis, caused by the parasite protozoan Tritrichomonas foetus, are venereal diseases that occur with long intercalving periods and abortion. The control of both diseases relies on microbiological testing and culling infected bulls. Vaccination and antibiotic treatment may help in controlling campylobacteriosis but are not recommended for trichomonosis control. Several regions of the world have active control programs for trichomonosis, not campylobacteriosis. In Argentina, the state of La Pampa aims to eradicate trichomonosis and campylobacteriosis by imposing annual diagnostic testing of every bull and slaughtering positive animals. Prior studies indicated a declining trend in the prevalence of campylobacteriosis and trichomonosis in La Pampa. It was also proposed that the prevalence of one disease could be estimated from the prevalence of the other. The purpose of this retrospective analysis of data gathered from 2008 to 2021 was to determine the La Pampa program’s efficacy. Descriptive statistics were employed to determine the reason behind the correlation between tricomonosis and campylobacteriosis diagnostic results. The outcomes refute the notion that this program of venereal eradication was a success. Furthermore, an excess of false positives in both diagnoses may have contributed to the correlation between the prevalences of campylobactriosis and trichomonosis. The practice of killing animals without verifying positive results hinders the determination of disease prevalence and results in the death of numerous healthy animals. [ABSTRACT FROM AUTHOR]

ABSTRACT The incidence of Vibrio vulnificus infections, with high mortality rates in humans and aquatic animals, has escalated, highlighting a significant public health challenge. Currently, reliable markers to identify strains with high virulence potential are lacking, and the understanding of evolutionary drivers behind the emergence of pathogenic strains is limited. In this study, we analyzed the distribution of virulent genotypes and phenotypes to discern the infectious potential of V. vulnificus strains isolated from three distinct sources. Most isolates, traditionally classified as biotype 1, possessed the virulence-correlated gene-C type. Environmental isolates predominantly exhibited YJ-like alleles, while clinical and diseased fish isolates were significantly associated with the nanA gene and pathogenicity region XII. Hemolytic activity was primarily observed in the culture supernatants of clinical and diseased fish isolates. Genetic relationships, as determined by multiple-locus variable-number tandem repeat analysis, suggested that strains originating from the same source tended to cluster together. However, multilocus sequence typing revealed considerable genetic diversity across clusters and sources. A phylogenetic analysis using single nucleotide polymorphisms of diseased fish strains alongside publicly available genomes demonstrated a high degree of evolutionary relatedness within and across different isolation sources. Notably, our findings reveal no direct correlation between phylogenetic patterns, isolation sources, and virulence capabilities. This underscores the necessity for proactive risk management strategies to address pathogenic V. vulnificus strains emerging from environmental reservoirs.IMPORTANCEAs the global incidence of Vibrio vulnificus infections rises, impacting human health and marine aquacultures, understanding the pathogenicity of environmental strains remains critical yet underexplored. This study addresses this gap by evaluating the virulence potential and genetic relatedness of V. vulnificus strains, focusing on environmental origins. We conduct an extensive genotypic analysis and phenotypic assessment, including virulence testing in a wax moth model. Our findings aim to uncover genetic and evolutionary factors that drive pathogenic strain emergence in the environment. This research advances our ability to identify reliable virulence markers and understand the distribution of pathogenic strains, offering significant insights for public health and environmental risk management.

Background: Vibrio parahaemolyticus is a pathogenic bacterium that affects shrimp aquaculture; its infection can lead to severe production losses of up to 90%. On the other hand, plant phenolic compounds have emerged as a promising alternative to combat bacterial infections. The antibacterial and anti-virulence activity of the plant phenolic compounds quercetin, morin, vanillic acid, and protocatechuic acid against two strains of V. parahaemolyticus (Vp124 and Vp320) was evaluated. Methods: The broth microdilution test was carried out to determine phenolic compounds' antibacterial activity. Moreover, the biofilm-forming ability of V. parahaemolyticus strains in the presence of phenolic compounds was determined by total biomass staining assay using the cationic dye crystal violet. The semisolid agar displacement technique was used to observe the effect of phenolic compounds on the swimming-like motility of V. parahaemolyticus. Results: Results showed that phenolic compounds inhibited both strains effectively, with minimum inhibitory concentrations (MICs) ranging from 0.8 to 35.03 mM. Furthermore, at 0.125 – 0.5 × MIC of phenolic compounds, V. parahaemolyticus biofilms biomass was reduced by 63.22 – 92.68%. Also, quercetin and morin inhibited the motility of both strains by 15.86 – 23.64% (Vp124) and 24.28 – 40.71% (Vp320). Conclusions: The results suggest that quercetin, morin, vanillic, and protocatechuic acids may be potential agents for controlling V. parahaemolyticus.

Vibrio vulnificus (Vv) is a bacterial pathogen native to warm and brackish water ecosystems that can cause fatal septicemia (Vv-vibriosis) in humans and various farmed fish species. From a One Health perspective, controlling Vv-vibriosis outbreaks on farms is essential not only for animal but also for human health, as it reduces the risk of Vv transmission to humans. Electrolyzed water (EW) is a sustainable control method, exhibiting transient disinfectant properties due to the formation of hypochlorous acid (HOCl). We hypothesized that EW could effectively reduce Vv populations in aquaculture facilities, preventing outbreak emergence. To test this hypothesis, survival assays in EW were conducted under varying conditions of salinity, pH, and free available chlorine (FAC). The results indicated that an intermediate concentration of FAC had a significant bactericidal effect on Vv populations regardless of the condition and tested strain. Consequently, the strategic use of EW could serve as an eco-friendly preventive and control measure against Vv-vibriosis by significantly decreasing the bacterial load in farm water.

BackgroundAliivibrio salmonicida is the causative agent of cold-water vibriosis in salmonids (Oncorhynchus mykiss and Salmo salar L.) and gadidae (Gadus morhua L.). Virulence-associated factors that are essential for the full spectrum of A. salmonicida pathogenicity are largely unknown. Chitin-active lytic polysaccharide monooxygenases (LPMOs) have been indicated to play roles in both chitin degradation and virulence in a variety of pathogenic bacteria but are largely unexplored in this context.ResultsIn the present study we investigated the role of LPMOs in the pathogenicity of A. salmonicida LFI238 in Atlantic salmon (Salmo salar L.). In vivo challenge experiments using isogenic deletion mutants of the two LPMOs encoding genes AsLPMO10A and AsLPMO10B, showed that both LPMOs, and in particular AsLPMO10B, were important in the invasive phase of cold-water vibriosis. Crystallographic analysis of the AsLPMO10B AA10 LPMO domain (to 1.4 Å resolution) revealed high structural similarity to viral fusolin, an LPMO known to enhance the virulence of insecticidal agents. Finally, exposure to Atlantic salmon serum resulted in substantial proteome re-organization of the A. salmonicida LPMO deletion variants compared to the wild type strain, indicating the struggle of the bacterium to adapt to the host immune components in the absence of the LPMOs.ConclusionThe present study consolidates the role of LPMOs in virulence and demonstrates that such enzymes may have more than one function.

Abstract Background Virulence determinants are crucial to the risk assessment of pathogens in an environment. This study investigated the presence of eleven key virulence-associated genes in Vibrio cholerae (n = 111) and Vibrio mimicus (n = 22) and eight virulence determinants in Vibrio alginolyticus (n = 65) and Vibrio parahaemolyticus (n = 17) isolated from six important water resources in Eastern Cape, South Africa, using PCR techniques. The multiple virulence gene indexes (MVGI) for sampling sites and isolates as well as hotspots for potential vibriosis outbreaks among sampling sites were determined statistically based on the comparison of MVGI. Result The PCR assay showed that all the V. cholerae isolates belong to non-O1/non-O139 serogroups. Of the isolates, Vibrio Cholera (84%), V. mimicus (73%), V. alginolyticus (91%) and V. parahaemolyticus (100%) isolates harboured at least one of the virulence-associated genes investigated. The virulence gene combinations detected in isolates varied at sampling site and across sites. Typical virulence-associated determinants of V. cholerae were detected in V. mimicus while that of V. parahaemolyticus were detected in V. alginolyticus. The isolates with the highest MVGI were recovered from three estuaries (Sunday river, Swartkopps river, buffalo river) and a freshwater resource (Lashinton river). The cumulative MVGI for V. cholerae, V. mimicus, V. alginolyticus and V. parahaemolyticus isolates were 0.34, 0.20, 0.45, and 0.40 respectively. The targeted Vibrio spp. in increasing order of the public health risk posed in our study areas based on the MVGI is V. alginolyticus > V. parahaemolyticus > V. cholerae > V. mimicus. Five (sites SR, PA5, PA6, EL4 and EL6) out of the seventeen sampling sites were detected as the hotspots for potential cholera-like infection and vibriosis outbreaks. Conclusions Our findings suggest that humans having contact with water resources in our study areas are exposed to potential public health risks owing to the detection of virulent determinants in human pathogenic Vibrio spp. recovered from the water resources. The study affirms the relevancy of environmental Vibrio species to the epidemiology of vibriosis, cholera and cholera-like infections. Hence we suggest a monitoring program for human pathogenic Vibrio spp. in the environment most especially surface water that humans have contact with regularly.

Abstract Canarium indicum offers the potential of usage in aquaculture. This study aimed to evaluate the utilization of C. indicum on growth performance, health, and resistance of Asian seabass Lates calcalifer challenged with Vibrio alginolyticus. The study employed a completely randomized design with seven treatments, namely positive control (K+), negative control (K-), vitamin control (KVit), antibiotic control (KAnt), doses of 5 g kg-1 (D05), 10 g kg-1 (D10), and 20 g kg-1 C. indicum (D20). The test feed was prepared with a coating method and fed for 30 days. On the 31st day of rearing, a challenge test was conducted by injecting V. alginolyticus intramuscularly at 106 CFU mL-1. The results showed that C. indicum treatment for 30 days had a significantly different effect (P0.05) from the negative control. The survival rate condition is identical to the cumulative survival condition which shows the highest mortality found in the positive control. The administration of C. indicum at a dose of 5 g kg-1 to 20 g kg-1 improved the growth performance and prevented V. alginolyticus infection. Highlight Research • C. indicum significantly increases the growth of Asian seabass. • C. indicum significantly enhances the immune response to V. alginolyticus infection in Asian seabass. • C. indicum can prevent V. alginolyticus infection as it resulted in a higher and cumulative survival than the positive control. • C. indicum can be developed as an immunostimulant for the prevention of vibriosis in Asian seabass at doses of 5 g kg-1 to 20 g kg-1.

Vibrio vulnificus (Vv) is a marine pathogen that can cause rapid death by septicemia (vibriosis) in humans and several fish species. This pathogen is considered a biomarker of climate change, as both its presence and vibriosis incidence in coastal environments are increasing because of global warming. Currently, gold-standard methods for Vv detection are all PCR-based, requiring expensive equipment and skilled personnel, which hinders their use on a global scale. The aim of this work was to design and test a more affordable method that could be used worldwide for both vibriosis diagnosis and pathogen monitoring in water. To this end, we functionalized thin film microelectrodes with thiolated single-stranded DNA sequences complementary to the species-specific genetic marker, the gene vvha, and monitored the impedance changes upon hybridization. We tested the biosensor specificity with synthetic and natural DNA samples (from cultures of Vv and V. cholerae, a closely related species) and determined the detectable concentration range. The results obtained showed that this biosensor was specific for Vv, achieving detection down to 1 pM synthetic DNA and DNA extracted from 102 bacteria mL−1, which is equivalent to that obtained by PCR. Consequently, this biosensor could be used on a global scale for vibriosis diagnostics, health risk studies and climate change monitoring, with potential application for in situ detection.

Vibrio vulnificus is an opportunistic pathogen in humans and exhibits pathogenic behavior in several aquaculture fish species. To date, in Brazil, there are no reports of V. vulnificus outbreaks in farmed fish. However, in 2019, sorubim (Pseudoplatystoma sp.) in the grow-out phase with clinical signs and cumulative mortality of 40% was registered. We aimed to identify and characterize the etiological agents of this outbreak. Seven moribund fish were sampled for bacteriological studies, and isolates were obtained from the brain and kidneys. Bacterial identification using matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF/MS) revealed V. vulnificus. One isolate, RP4, was used for identification via dnaJ and 16S rRNA gene sequencing and antimicrobial susceptibility evaluation. Sorubim juveniles were experimentally challenged with RP4 isolate via intracelomic injection (IC, 107 colony-forming units [CFU] fish−1) and immersion bath (IB, 106 CFU mL−1 for 30 min). Identities to V. vulnificus of dnaJ and 16S rRNA genes by BLAST analysis were higher than 92% and 98%, respectively. Susceptibility to oxytetracycline, florfenicol, and other antimicrobial molecules was also observed. In the IC-challenged group, the mortality rate was 100% with V. vulnificus recovered from fish organs (brain, liver, spleen, and kidney). Additionally, splenic endothelium alterations were observed in the IC group. On the contrary, the control and IB groups did not develop any clinical signs, mortality, or bacterial recovery after 7 days of challenge. To the best of our knowledge, this is the first report of pathogenic V. vulnificus in farmed Pseudoplatystoma sp. [ABSTRACT FROM AUTHOR]

Indiscriminate use of antibiotics has led to the emergence of antibiotic‐resistant microbes and the loss of natural flora in aquaculture systems necessitating the ban of many of these chemotherapeutants in aquaculture. Actinobacteria play a profound role in the biogeochemical cycling in the marine environment and represent the principal source of secondary metabolites with antimicrobial property. In the present study, 98 marine‐derived actinomycete isolates were screened for antimicrobial activity against the common aquatic pathogens. A potent actinomycete isolate S26, identified as Streptomyces variabilis based on 16 S ribosomal RNA (rRNA) gene sequencing was then checked for the production of antibiotic in five different fermentation media and the one which showed maximum production was chosen for further study. Optimization of the fermentation medium for secondary metabolite production was carried out by response surface methodology (RSM) using DESIGN EXPERT. The analysis of variance (ANOVA) of the quadratic regression model demonstrated that the model was highly significant for the response concerned that is, antimicrobial activity as evident from the Fisher's F‐ test with a very low probability value [(P model>F) = 0.0001]. Of the 10 different solutions suggested by the software, the most suitable composition was found to be starch, 1.38%; soy powder, 0.88%; ammonium sulfate, 0.16% and salinity, 27.76‰. S. variabilis S26 cultured in the optimized production medium was applied in the Penaeus monodon larval rearing system and the total Vibrio count and survival rate were estimated. S. variabilis S26 treatment showed a significant reduction in vibrios and conferred better protection to P. monodon in culture system compared with control. [ABSTRACT FROM AUTHOR]

Vibriosis is caused by Vibrio anguillarum in various species of aquaculture. A novel, secure, and stable vaccine is needed to eradicate vibriosis. Here, for reverse vaccinology and plant-based expression, the outer membrane protein K (OmpK) of V. anguillarum was chosen due to its conserved nature in all Vibrio species. OmpK, an ideal vaccine candidate against vibriosis, demonstrated immunogenic, non-allergic, and non-toxic behavior by using various bioinformatics tools. Docking showed the interaction of the OmpK model with TLR-5. In comparison to costly platforms, plants can be used as alternative and economic bio-factories to produce vaccine antigens. We expressed OmpK antigen in Nicotiana tabacum using Agrobacterium -mediated transformation. The expression vector was constructed using Gateway® cloning. Transgene integration was verified by polymerase chain reaction (PCR), and the copy number via qRT-PCR, which showed two copies of transgenes. Western blotting detected monomeric form of OmpK protein. The total soluble protein (TSP) fraction of OmpK was equivalent to 0.38% as detected by ELISA. Mice and fish were immunized with plant-derived OmpK antigen, which showed a significantly high level of anti-OmpK antibodies. The present study is the first report of OmpK antigen expression in higher plants for the potential use as vaccine in aquaculture against vibriosis, which could provide protection against multiple Vibrio species due to the conserved nature OmpK antigen. • Outer membrane protein K (OmpK) demonstrates immunogenic potential in silico. • OmpK antigen for immunization is produced in cost-effective plant bio-factories. • OmpK produced in plants induced a strong antibody response in mice and fish. • Vibriosis in aquaculture may be eradicated by cost-effective subunit vaccination. [ABSTRACT FROM AUTHOR]

Aquaculture is developing rapidly and plays an important role in providing animal protein to the world's growing population. However, increasing mortality from bacterial disease outbreaks in important species poses a challenge to production progress in this sector. In order to reduce the impact of these diseases, rapid and accurate pathogen identification is essential for disease management, early detection and the continued health of aquaculture. The aim of this review is to summarise studies on the identification and diagnosis of Vibrio pathogens in aquatic organisms by MALTI-TOF MS (Matrix-Assisted Laser Desorption Ionisation Time-of-Flight Mass Spectrometry), a rapid identification method based on protein profiling of bacteria. The profiles of bacterial protein obtained are compared with a global microbial protein library for identification. This study demonstrates the potential of using MALDI-TOF MS for the detection of Vibrio pathogens in aquaculture in studies published between 2015 and 2024. While purchasing a time-of-flight mass spectrometer is expensive when compared to conventional and molecular identification methods. It also appears to be much more efficient in terms of time spent on identification. MALDI-TOF MS has been shown to be simple to use in fish identification laboratories. [ABSTRACT FROM AUTHOR]

In the last two decades, episodes of mass mortality in benthic communities have often been associated with climatic anomalies, but the ultimate mechanisms through which they lead to death have rarely been identified. This study reports a mass mortality of wild sponges in the Aegean Sea (Turkey, Eastern Mediterranean), which affected the keratose demosponge Sarcotragus foetidus in September 2021. We examined the occurrence of thermo-dependent bacteria of the genus Vibrio in the sponges, identified through 16S rRNA of colonies isolated from sponge tissue in specific culturing media. Six Vibrio sequences were identified from the sponges, three of them being putatively pathogenic (V. fortis, V. owensii, V. gigantis). Importantly, those Vibrios were isolated from only tissues of diseased sponges. In contrast, healthy individuals sampled in both summer and winter led to no Vibrio growth in laboratory cultures. A 50  years record of sea surface temperature (SST) data for the study area reveals a progressive increase in temperature from 1970 to 2021, with values above 24°C from May to September 2021, reaching an absolute historical maximum of 28.9°C in August 2021. We hypothesize that such elevated SST values maintained for several months in 2021 promoted proliferation of pathogenic Vibrio species (thermo-dependent bacteria) in S. foetidus, triggering or aggravating the course of sponge disease. Thus, vibrioisis emerges as one of the putative mechanisms through which global water warming in the Mediterranean Sea translates into sponge mortality. The historical time course of temperature data for the studied area in the Aegean Sea predicts that recurrent waves of elevated SST are likely to occur in the coming summers. If so, recurrent disease may eventually eliminate this abundant sponge from the sublittoral in the midterm, altering the original bathymetric distribution of the species and compromising its ecological role. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the relationship between seasonal variations, water parameters and the prevalence of Vibriosis in Gilthead seabream. A total of 160 Gilthead seabream fish were sampled over the course of 1 year from private earthen pond farms in the Suez Canal area and examined for abnormalities and internal lesions. Vibrio alginolyticus, the causative agent of Vibriosis, was isolated and characterized from the sampled Gilthead seabream fish. The study revealed a significant correlation between different seasons and the prevalence of V. alginolyticus, with lower occurrence during autumn. Analysis of water parameters showed that toxic ammonia concentration was not effective in distinguishing between positive and negative cases of V. alginolyticus. Dissolved oxygen showed weak predictive ability for the occurrence of V. alginolyticus, while temperature demonstrated moderate potential as a predictor of its prevalence. pH values, organic matter concentrations and salinity showed no significant association with the occurrence of V. alginolyticus. Experimental challenges highlighted the vulnerability of Gilthead seabream to V. alginolyticus and emphasized the impact of environmental factors, such as pH and toxic ammonia, on their mortality and survival. The study emphasizes the importance of considering seasonal changes and water quality parameters in managing V. alginolyticus in mariculture. It underscores the need for careful monitoring and control of environmental factors to ensure the health and well‐being of cultured fish populations. The findings contribute to our understanding of Vibriosis management and provide valuable insights for developing effective strategies in the aquaculture industry. [ABSTRACT FROM AUTHOR]

Abstract Vibriosis is a bacterial disease in fish caused by the Gram negative bacterium Vibrio anguillarum with severe impact on rainbow trout (Oncorhynchus mykiss) farming. Sustainable control methods should be developed and we here show that marker assisted selective breeding of fish naturally resistant to the disease is feasible. We have validated the use of a single nucleotide polymorphism (SNP) marker SNP AX-89,945,921 (QTL on chromosome 21). The QTL was previously found associated with resistance to vibriosis and described following a genome wide association analysis (GWAS) of trout exposed to the bacterium. For this validation spawners were genotyped by use of the 57 K Axiom®Trout Microarray (Affymetrix) and homozygous male fish carrying the allele with the SNP AX-89,945,921 were then selected and used to fertilize eggs from outbred female trout resulting in fish all carrying the SNP (QTL-fish). Control fish (non-QTL fish) were produced by fertilizing the same batch of eggs by use of male parents negative for the SNP. The fish were exposed in freshwater to V. anguillarum (water bath infection) at 19 C°. A total of 900 fish were challenged in a common garden set-up in triplicate. A bacterial solution of V. anguillarum (serotype O1) was added to each of three freshwater fish tanks, each with 150 QTL and 150 non-QTL fish. Fish were tagged by tail fin cut (upper/lower) to discern the two groups, whereafter fish were monitored around the clock to detect disease signs and remove moribund fish. Clinical vibriosis developed within two days in non-QTL-fish (overall morbidity of 70%). QTL fish developed clinical signs later and the morbidity was significantly lower and did not reach 50%. Rainbow trout farming may benefit from using the QTL associated with higher resistance towards vibriosis. The effect may be optimized in the future by use of both male and female parents homozygous for the marker allele.

Aquaculture can suffer from heavy losses caused by vibriosis, which denotes diseases caused by Vibrio bacteria. Due to disadvantages of available measures, mostly involving the use of antibiotics, to control these bacteria, novel measures are still needed. Therefore, aiming at an innovative solution for that issue in a long term, we investigated the inhibitory effects of the sediment bioelectrochemical system (SBES) on a V. harveyi strain (Vh) and a V. parahaemolyticus strain (Vp). SBESs were installed in test pond models that were lab-scale plastic tanks containing artificial brackish water, while the resembling systems not having SBESs were used as the controls. Once the SBES stably generated electricity (at ca. 0.5 mA), the tests with the Vibrio strains were conducted by: (i) supplementing the Vibrio cell suspensions directly into the tank waters, (ii) immersing the Vibrio cells suspensions each in an isolated axenic space into the tank environments, and (iii) adding the filtered tank waters after taken out of the tanks to the Vibrio cells. Based on plate enumeration to evaluate the inhibitory effects of such treatments on the Vibrio strains, we discovered that almost 100% of both Vh and Vp cells could not grow after 5 min in contact with the SBES water while more than 80% of them could still grow after 1–2 h in contact with the water from the control tanks. Paralleling tests showed that the SBES water was also toxic to an Escherichia coli strain but only slightly inhibited a Bacillus pumilus strain and a Lactobacillus plantarum strain, reducing their growths by only about 60% and 30%, respectively. Further tests revealed that the effects were not due to suspected proteinacous components or metal contents or peroxides in the SBES water. On the other hand, applying a redox potential of 20 mV (vs. Ag/AgCl), which was the anode potential measured in the SBES, onto a graphite rod immersed in Vh cell suspension led to the growth inhibition to 90% of the cells, although the unpoised graphite rod also seemed toxic, inhibiting ca. 60% of Vh cells. A similar experiment with titanium (known to be non-toxic to bacteria), instead of graphite, clearly showed the vibrio-inhibiting effect of the applied redox potential. Altogether, the results directly evidence the inhibitory effect of the SBES on V. harveyi and V. parahaemolyticus. This effect, together with the mild effect on the beneficial bacilli, implies that SBES integration in aquaculture ponds can be a promising novel technological option that allow controlling vibriosis in-situ while minimizing the uses of antibiotics or other chemicals, toward more sustainable aquaculture practices.

Lumpfish (Cyclopterus lumpus) have become the predominant cleaner fish species used in North American salmon aquaculture. Vibrio anguillarum is a frequent pathogen of lumpfish in Atlantic Canada, and current vaccines against local isolates conferred low to moderate efficacy. This study evaluated the safety and efficiency of a V. anguillarum autogenous vaccine under controlled and field conditions. Two safety trials were conducted following the Canadian Food Inspection Agency (CFIA) regulations before field trial testing. The first safety trial was a common garden assay, and 250 PIT-tsgged lumpfish were used for five treatments per tank (PBS-negative control, Lab vaccine-positive control, autogenous intraperitoneal (IP) vaccine, autogenous dip vaccine, autogenous dip-IP boosted vaccine) in triplicates. Weight, gross pathology, and IgM titers were evaluated to determine the vaccine’s safety. After 10 weeks post-vaccination (wpv), lumpfish were bath-challenged with a lethal dose (1.24 x 106 CFU/mL) of V. anguillarum serotype O2. Survival rate, IgM titers, memory immune response, and cross-immune protection were evaluated. The second safety trial was conducted using a double vaccine dose in two groups, PBS and autogenous IP. The gross pathology score indicated a normal immune response without tissue damage, and no mortality nor fish health issues were observed in the immunized animals. The IP route of administration conferred the highest protection against the V. anguillarum challenge. The autogenous vaccine conferred long-term immunity but did not confer cross-protection against V. anguillarum serotype O1. To evaluate the efficiency of the autogenous vaccine under field conditions, 58,976 naïve lumpfish (8-10 g) were IP immunized with either the autogenous vaccine or the commercial Forte micro IV vaccine. After 7 wpv, the lumpfish were equally distributed into eight sea cages and co-cultivated with Atlantic salmon smolts (60,000 per cage). Lumpfish IgM titers, tissue bacterial loads, mortality, and sea lice count on salmon were monitored. The autogenous vaccine and Forte vaccine confer acceptable protection to the lumpfish in sea cages. No significant difference was observed between lumpfish vaccinated with autogenous and commercial vaccines under field conditions.

Simple Summary: Vibrio gigantis was first identified as an opportunistic pathogen of European seabass broodstock in Türkiye. The bacterium was isolated from the reproductive organs, liver, and spleen of diseased fish. A representative isolate C24 was unambiguously identified as V. gigantis based on high whole-genome average nucleotide identity values (ANI > 97.7%). Despite causing notable problems in broodstock, the V. gigantis C24 isolate exhibited low to moderate virulence in experimentally challenged juvenile European seabass. In this study, V. gigantis strain C24 was isolated from cases of winter mortalities of hatchery-reared European seabass (Dicentrarchus labrax) broodstock in Türkiye. The first mortalities were reported in September 2016 and occurred annually in early autumn/late winter until the end of February 2019, when 15% of accumulated mortality was recorded. Diseased moribund fish exhibited general septicemic signs, including dermal ulcerations with hemorrhagic margins, distended abdomens, and hemorrhages below the pectorals, pelvic fins, and at the operculum. Postmortem findings showed congestion in several internal organs, hemorrhagic ascitic fluid, and congested prolapsed anal openings. The representative bacterial isolate V. gigantis strain C24 was characterized as Gram-negative, motile, nitrite-producing, and as vibrio static agent O/129-sensitive. The full-length 16S rRNA sequence (Accession No. ON778781) and gyrB gene sequence (Accession No. ON792326) of the C24 strain showed high similarity to V. gigantis strains. Moreover, the whole-genome average nucleotide identity (ANI) values (ANI > 97.7%) against four V. gigantis strains above the species demarcation limit unambiguously identified the C24 isolate as a member of this species. A preliminary virulence-gene analysis showed that the V. gigantis isolate C24 encoded at least three exotoxins, including two aerolysins and a thermolabile hemolysin. The experimental infection showed that the C24 isolate exhibited low to moderate virulence in experimentally infected European seabass juveniles. Interestingly, antimicrobial susceptibility testing revealed that the C24 isolate was susceptible to nalidixic acid, ciprofloxacin, and several other antibiotics but resistant to tilmicosin, kanamycin, streptomycin, and ampicillin. To our knowledge, this study is the first to report that V. gigantis could be considered an emerging bacterial pathogen in Türkiye, and it may threaten the international European seabass production. [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus exhibits severe pathogenicity in humans and animals worldwide. In this study, genome sequencing and comparative analyses were conducted for in-depth characterization of the virulence factor (VF) repertoire of V. parahaemolyticus strain LC, which presented significant virulence to shrimp Litopenaeus vannamei. Strain LC, harboring two circular chromosomes and three linear plasmids, demonstrated ≥98.14% average nucleotide identities with 31 publicly available V. parahaemolyticus genomes, including 13, 11, and 7 shrimp-, human-, and non-pathogenic strains, respectively. Phylogeny analysis based on dispensable genes of pan-genome clustered 11 out of 14 shrimp-pathogenic strains and 7 out of 11 clinical strains into two distinct clades, indicating the close association between host-specific pathogenicity and accessory genes. The VFDB database revealed that 150 VFs of LC were mainly associated with the secretion system, adherence, antiphagocytosis, chemotaxis, motility, and iron uptake, whereas no homologs of the typical pathogenic genes pirA, pirB, tdh, and trh were detected. Four genes, mshB, wbfT, wbfU, and wbtI, were identified in both types of pathogenic strains but were absent in non-pathogens. Notably, a unique cluster similar to Yen-Tc, which encodes an insecticidal toxin complex, and diverse toxin–antitoxin (TA) systems, were identified on the mobile genetic elements (MGEs) of LC. Conclusively, in addition to the common VFs, various unique MGE-borne VFs, including the Yen-Tc cluster, TA components, and multiple chromosome-encoded chitinase genes, may contribute to the full spectrum of LC virulence. Moreover, V. parahaemolyticus demonstrates host-specific virulence, which potentially drives the origin and spread of pathogenic factors. [ABSTRACT FROM AUTHOR]

The lipidic extract of Undaria pinnatifida, one of the worst invasive species, was investigated for its potential exploitation in biotechnological applications. The antimicrobial activity of the lipidic extract in three different portions (blade, sporophyll, and holdfast) was assessed by using the Kirby–Bauer method, while the antioxidant activity was evaluated by the TEAC, ORAC, and Folin–Ciocalteu assays. NMR spectroscopy and thin-layer chromatography were employed for the chemical characterization. The extracts showed antibacterial activity against several of the tested Vibrio species: V. aestuarinus, V. fischeri, V. furnisii, V. inusitatus, V. litoralis, and V. mediterranei, including some pathogens for farmed fish. Intriguing antioxidant activity was recorded, with the highest value in the blade (126.907 ± 28.993 mmol Trolox equivalent/g TEAC). Free, saturated, unsaturated, and polyunsaturated fatty acids were highlighted by 1D and 2D NMR spectroscopy. The presence of ω-3 and ω-6 PUFAs indicates the importance of this algal species in the food industry. We suggest the employment of U. pinnatifida as source of new and safer therapeutic agents to control fish and shellfish diseases due to vibriosis, as well as a source of natural antioxidants that are useful for human health, considering the growing interest in the development of strategies for invasive seaweed control. [ABSTRACT FROM AUTHOR]