Search Results (109)

Marine heatwaves (MHWs) are an emerging challenge for aquaculture, increasing the frequency and severity of disease outbreaks in farmed fish, weakening immunocompetence and compromising overall health and survival. As climate change stressors intensify, there is an urgent need for cost-effective and environmentally friendly strategies to enhance fish resilience. This study investigated the efficacy of Laminaria digitata, a brown macroalga, included in aquafeeds as powder (0.3% and 1.5%) or extract (0.3%) in improving the stress response of juvenile gilthead seabream (Sparus aurata) co-exposed to Vibrio harveyi infection during a category III MHW event. Under control conditions, L. digitata supplementation maintained or improved fish growth performance and overall well-being. After MHW exposure, the 1.5% powdered and 0.3% extract diets were more effective in mitigating thermal stress, reducing liver oxidative stress and lowering plasma cortisol levels. In infected fish, these diets improved resistance to V. harveyi, with reduced cortisol and alanine aminotransferase concentrations indicating hepatoprotective properties, and lower lipid peroxidation and decreased antioxidant enzyme activities reflecting an amplified capacity to counteract oxidative stress induced by inflammation. Overall, L. digitata is a promising aquafeed supplement, with the 1.5% powdered form offering a cost-effective alternative to the extract without compromising efficacy. Full article

Vibrio species are among the primary pathogenic bacteria affecting abalone aquaculture, posing significant threats to farming practices. Current clinical control predominantly relies on antibiotics, which can result in antibiotic residues in both abalone and the surrounding marine environments. Lactobacillus plantarum (LP) has been shown to release bioactive antagonistic substances and exhibits potent inhibitory effects against marine pathogenic bacteria. This study aimed to screen and characterize the probiotic properties of LP strains isolated from rice wine lees to develop a novel biocontrol strategy against Vibriosis in abalone. The methods employed included selective media cultivation, streak plate isolation, and single-colony purification for strain screening, followed by Gram staining, 16S rDNA sequencing, and phylogenetic tree construction using MEGA11 for identification. The resilience, antimicrobial activity, and in vivo antagonistic efficacy of the strains were evaluated through stress tolerance assays, agar diffusion tests, and animal experiments. The results demonstrated the successful isolation and purification of four LP strains (NDMJ-1 to NDMJ-4). Phylogenetic analysis revealed closer genetic relationships between NDMJ-3 and NDMJ-4, while NDMJ-1 and NDMJ-2 were found to be more distantly related. All strains exhibited γ-hemolytic activity, bile salt tolerance (0.3–3.0%), and resistance to both acid (pH 2.5) and alkali (pH 8.5), although they were temperature sensitive (inactivated above 45 °C). The strains showed susceptibility to most of the 20 tested antibiotics, with marked variations in hydrophobicity (1.91–93.15%) and auto-aggregation (13.29–60.63%). In vitro antibacterial assays revealed that cell-free supernatants of the strains significantly inhibited Vibrio parahaemolyticus, V. alginolyticus, and V. natriegens, with NDMJ-4 displaying the strongest inhibitory activity. In vivo experiments confirmed that NDMJ-4 significantly reduced mortality in abalone infected with V. parahaemolyticus. In conclusion, the LP strains isolated from rice wine lees (NDMJ-1 to NDMJ-4) possess robust stress resistance, adhesion capabilities, and broad antibiotic susceptibility. Their metabolites exhibit significant inhibition against abalone-pathogenic Vibrios, particularly NDMJ-4, which demonstrates exceptional potential as a candidate strain for developing eco-friendly biocontrol agents against Vibriosis in abalone aquaculture. Full article

Extreme weather events, such as marine heatwaves (MHWs), pose serious threats to the aquaculture sector, facilitating the occurrence of disease outbreaks and compromising farmed animals’ welfare and survival. Hence, finding eco-innovative strategies to improve animal immunocompetence is essential to assure aquaculture’s sustainability and resilience in a rapidly changing ocean. This study evaluated the immunostimulatory potential of Laminaria digitata powder (0.3% and 1.5%) and extract (0.3%) in juvenile gilthead seabream (Sparus aurata) exposed to a Vibrio harveyi outbreak during a Category III MHW event (T = 25.7 °C). Overall, L. digitata supplementation did not significantly affect fish immunocompetence under optimal rearing conditions (T = 21.4 °C; no infection), nor did it induce any adverse effects. However, both the powder (1.5%) and extract (0.3%) forms of L. digitata supplementation effectively mitigated the negative impacts prompted by the MHW and Vibrio harveyi infection—evidenced by improvements in fish health indicators, hematological parameters, leukocyte viability, granulocyte proportions, and reductions in peroxidase activity and immunoglobulin M levels. From an economic standpoint, supplementation with 1.5% L. digitata powder emerged as the most promising strategy, offering a practical balance between effectiveness and affordability for large-scale applications. These findings highlight the potential of L. digitata as an immunostimulatory aquafeed supplement, with promising benefits for fish health and resilience under adverse rearing conditions. Full article

Vibrio harveyi is a significant pathogen in marine aquaculture, causing vibriosis in various marine species. This study presents a comparative genomic analysis of two V. harveyi strains, N8T11 and 45T2, which exhibit differing virulence profiles. Virulence assays revealed that N8T11 caused 92% mortality in infected fish, while 45T2 resulted in 0% mortality. Whole-genome sequencing revealed that strain N8T11 harbors five plasmids (pN8T11a, pN8T11b, pN8T11c, pN8T11d and pN8T11e) absent in 45T2, encoding genes potentially linked to virulence, such as siderophore-mediated iron acquisition and stress response mechanisms. Pan-genome analysis highlighted substantial genomic plasticity within V. harveyi, with mobile genetic elements, including plasmids and prophages, contributing to horizontal gene transfer. Conjugation experiments demonstrated that all five N8T11 plasmids can transfer to 45T2 with efficiencies up to 87%, with pN8T11b remaining stable across multiple subcultures, enabling the dissemination of virulence-associated genes. These findings suggest that plasmid-mediated gene transfer plays a role in the virulence variability observed between V. harveyi strains. This study contributes to understanding the genomic factors underlying pathogenicity in V. harveyi and provides insights for future research aimed at controlling vibriosis in aquaculture. Full article

Ornamental fish represent a significant aquaculture sector with notable economic value, yet their contribution to antibiotic residues and resistance remains underrecognized. This review synthesizes evidence on widespread and often unregulated antibiotic use—including tetracyclines and fluoroquinolones—in ornamental fish production, transportation, and retail, primarily targeting bacterial diseases such as aeromonosis and vibriosis. Pathogenic microorganisms including Edwardsiella, Flavobacterium, and Shewanella spp. cause diseases like hemorrhagic septicemia, fin rot, skin ulcers, and exophthalmia, impairing fish health and marketability. Prophylactic and therapeutic antibiotic applications elevate antibiotic residues in fish tissues and carriage water, thereby selecting for antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). These resistant elements pose significant risks to fish health, human exposure via direct contact and bioaerosols, and environmental health through contamination pathways. We emphasize the urgent need for a holistic One Health approach, involving enhanced surveillance, stringent regulatory oversight, and adoption of alternative antimicrobial strategies, such as probiotics and advanced water treatments. Coordinated global actions are crucial to effectively mitigate antibiotic resistance within the ornamental fish industry, ensuring sustainable production, safeguarding public health, and protecting environmental integrity. Full article

The Vibrio genus represents a critical group of bacterial pathogens in the marine environment globally, leading to massive mortality in the aquaculture industry. Diagnosing vibriosis, an infection caused by Vibrio species, in clinical samples poses challenges due to its non-specific clinical manifestations. In this study, we developed a TaqMan probe-based multiplex real-time PCR method for the simultaneous detection and quantification of four Vibrio pathogens: Vibrio anguillarum (Va), Vibrio alginolyticus (Val), Vibrio harveyi (Vh), and Vibrio scophthalmi (Vsc). The assay targets conserved intra-species regions and specific inter-species regions using specific primers and TaqMan probes to ensure specificity. Sensitivity analysis demonstrated that the multiplex real-time PCR assay could simultaneously detect the four different bacteria, with detection limits of 26–60 copies per reaction, making it 100 times more sensitive than conventional PCR assays. Additionally, the assay exhibited high reproducibility, with intra- and inter-group coefficients of variation below 1.4%. A total of 63 clinical samples was analyzed using this established assay, which successfully detected both single and mixed infections. These results demonstrate that the multiplex quantitative PCR assay is a rapid, specific, and sensitive diagnostic tool for the detection of Va, Val, Vh, and Vsc, making it suitable for monitoring these bacteria in both single- and co-infected clinical samples. Full article

Vibrio parahaemolyticus is a pathogenic bacterium that threatens food safety by infecting humans and marine organisms. Among its virulence factors, lecithin-dependent hemolysin (vpLDH) has been identified as a promising target for attenuating its pathogenicity. This study explores the inhibitory mechanisms of three natural flavonoids—quercetin, morin, and EGCG—on LDH using enzyme kinetics, fluorescence quenching, and molecular dynamics simulations. The flavonoids quercetin, morin, and EGCG inhibited vpLDH phospholipase A2 activity via a competitive mechanism with inhibition constants of 17.1, 17.27, and 24.24 µM, respectively. Fluorescence quenching experiments confirmed that the evaluated flavonoids formed a stable, non-fluorescent complex (1:1 stoichiometry) with vpLDH. Also, via Stern–Volmer plots, the dissociation constant was calculated (Kd); quercetin showed the highest affinity, followed by morin and EGCG. Molecular dynamics simulations revealed that all evaluated ligands bind to the vpLDH active site vicinity with oscillations < 1.7 nm (100 ns), indicating that both the flavonoids and substrate vpLDH complexes are stable. These findings demonstrate that quercetin, morin, and EGCG are stable competitive inhibitors, highlighting their potential as natural anti-virulence agents against V. parahaemolyticus. Full article

This study aimed to isolate AHL-degrading bacteria from the intestine of Penaeus vannamei and evaluate their ability to control pathogenic Vibrio harveyi in P. vannamei larvae. Twenty-seven isolates were obtained from the digestive tract of healthy Pacific white shrimp juveniles (P. vannamei) after six cycles of pasteurization at 70 °C, but only three isolates (E₁LP₂, E₂LP₁, and E₂LP₂) could degrade AHL. The 16S sequence results gave a high identity (>95%) with Bacillus sp. The isolates exhibited quorum-quenching abilities by degrading AHLs, thereby disrupting Vibrio quorum sensing and virulence. In Zoea and Mysis, the challenged larvae plus the administration of E₁LP₂ resulted in the lowest survival compared to the other groups. Isolates degrading N-acyl homoserine lactone improved the survival of shrimp Zoea and Mysis larvae when challenged with pathogenic V. harveyi. This is the first report on the use of quorum-sensing disrupter bacteria in P. vannamei larval shrimp culture. Our findings suggest that these Bacillus spp. strains have potential as biocontrol agents for sustainable shrimp aquaculture, reducing the reliance on antibiotics while mitigating vibriosis outbreaks. Full article

Background: The aquaculture sector is vital for food supply and marine species conservation. However, vibriosis poses significant threats, affecting fish and invertebrates. Vibrio harveyi outbreaks are increasing due to global warming-driven expansion of virulent strains. Methods: This study investigates the bactericidal potential of in situ-generated electrolyzed water (EW) as a complementary strategy to antibiotic therapy. Strains of V. harveyi isolated from diseased fish were exposed to EW under varying conditions of salinity (1.5 and 3%), pH (5, 6.5, and 7.5), and free available chlorine (FAC) (5, 20, 25, and 125 ppm) to reduce bacterial concentrations. Results: EW demonstrated high bactericidal potential at 20–25 ppm FAC and non-acidic pH, reducing bacterial populations by over four logarithmic units within 15 min. Efficacy diminished when EW was stored for days. Conclusions: EW shows a promising disinfection method during vibriosis outbreaks and as a preventive measure during stress in aquaculture. Its advantages include on-site production and avoidance of concentrated chemicals, which minimize health risks. Full article

Seaweeds are critically important for the maintenance of biodiversity in marine aquaculture ecosystems, as they can inhibit the growth of Vibrio. Here, we determined the optimal environmental parameters for co-culturing green macroalgae (Ulva pertusa) and red macroalgae (Gracilariopsis lemaneiformis) with Chinese scallop (Chlamys farreri) by measuring dissolved oxygen (DO), pH, and the strength of Vibrio inhibition under laboratory conditions and validating the effectiveness of this optimal co-culture system from the perspectives of nutrient levels, enzyme activities, and microbial diversity. The results show that co-culturing 30 g of seaweed and three scallops in 6 L of seawater with aeration in the dark (1.25 L min⁻¹, 12:12 h L:D) significantly decreased the number and abundance of Vibrio after 3 days. The activities of superoxide dismutase, catalase, pyruvate kinase, and lactate dehydrogenase in C. farreri were significantly higher, indicating that its immune defense and metabolism enhanced in this optimal co-culture system. High DO and pH levels significantly decreased the alpha diversity of microorganisms, and the abundance of pathogenic microorganisms decreased. The optimal co-culture system was effective for the control of vibriosis. Generally, our findings suggest that seaweeds could be used to enhance the aquaculture environment by conferring healthy and sustainable functions in the future. Full article

Vibrio parahaemolyticus is a ubiquitous inhabitant of estuarine and marine environments that causes vibriosis in aquatic animals and food poisoning in humans. Accessory colonizing factor (ACF) is employed by Vibrio to assist in the colonization and invasion of host cells leading to subsequent illnesses. In this work, ΔacfA, an in-frame deletion mutant strain lacking the 4th to the 645th nucleotides of the open reading frame (ORF) of the acfA gene, and the complementary strain acfA⁺ were constructed to decipher the function of AcfA in V. parahaemolyticus. The deletion of acfA had no effect on bacterial growth but resulted in a significant reduction in biofilm formation, hemolytic activity, mucus adhesion, and the accumulated mortality of zebrafish, compared to the wild-type strain and the complementary strain acfA⁺. Additionally, AcfA was involved in adapting to stressors, such as H₂O₂, EDTA, and acid, in V. parahaemolyticus. Furthermore, RNA-Seq transcriptome analysis was conducted to identify global gene transcription alterations resulting from deletion of the acfA gene. A total of 416 differentially expressed genes were identified in the ΔacfA vs. wild-type comparison, with 238 up-regulated genes and 178 down-regulated genes. The expression of genes associated with the type III secretion system, type VI secretion system, and oligopeptide permeases system were significantly reduced, and yet the expression of genes associated with cell envelope biosynthesis and response regulation system were enhanced dramatically in the absence of the acfA gene compared to the wild-type strain. These findings suggest that AcfA may play a role in the overall success of pathogenesis and the cell envelope stress response of V. parahaemolyticus. Full article

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. Full article

Vibriosis caused by Vibrio vulnificus is a major problem in aquatic animals, particularly brown marble groupers (Epinephelus fuscoguttatus). V. vulnificus biotype I has recently been isolated and classified into subgroups SUKU_G1, SUKU_G2, and SUKU_G3 according to the different types of virulence genes. In a previous study, we have shown that biotype I V. vulnificus strains were classified into three subgroups according to the different types of virulence genes, which exhibited different phenotypes in terms of growth rate and virulence. To gain insight into the different genetic features revealed by the potential virulence mechanisms of V. vulnificus in relation to a spectrum of pathogenesis, comparative genomic analyses of three biotype I V. vulnificus strains belonging to different subgroups (SUKU_G1, SUKU_G2, and SUKU_G3) were performed. The V. vulnificus genome is composed of two circular chromosomes with average sizes of 3 Mbp and 1.7 Mbp that are evolutionarily related based on the analysis of orthologous genes. A comparative genome analysis of V. vulnificus revealed 5200 coding sequences, of which 3887 represented the core genome and the remaining 1313 constituted the dispensable genome. The most virulent isolate (SUKU_G1) carries unique enzymes that are important for lipopolysaccharide (LPS) and capsular polysaccharide (CPS) synthesis, as well as flagellar glycosylation, and harbors another type of repeat in toxin (RTX) and bacterial defense mechanisms. The less virulent isolate (SUKU_G2) shares enzymes related to CPS biosynthesis or flagellar glycosylation, while the avirulent isolate (SUKU_G3) and a less virulent isolate (SUKU_G2) share enzymes related to the production of rare sugars. Interestingly, the isolates from the three subgroups containing specific CMP-N-acetylneuraminate-producing enzymes that are correlated with their growth abilities. Collectively, these observations provide an understanding of the molecular mechanisms underlying disease pathogenesis and support the development of strategies for bacterial disease prevention and control. Full article

The vast, untapped potential of the world’s oceans is revealing groundbreaking advancements in human health and vaccination. Microalgae such as Nannochloropsis spp. and Dunaliella salina are emerging as resources for recombinant vaccine development with specific and heterologous genetic tools used to boost production of functional recombinant antigens in Dunaliella salina and Nannochloropsis spp. to induce immunoprotection. In humans, several antigens produced in microalgae have shown potential in combating diseases caused by the human papillomavirus, human immunodeficiency virus, hepatitis B virus, influenza virus, Zika virus, Zaire Ebola virus, Plasmodium falciparum, and Staphylococcus aureus. For animals, microalgae-derived vaccine prototypes have been developed to fight against the foot-and-mouth disease virus, classical swine fever virus, vibriosis, white spot syndrome virus, and Histophilus somni. Marine organisms offer unique advantages, including the ability to express complex antigens and sustainable production. Additionally, the oceans provide an array of bioactive compounds that serve as therapeutics, potent adjuvants, delivery systems, and immunomodulatory agents. These innovations from the sea not only enhance vaccine efficacy but also contribute to broader immunological and general health. This review explores the transformative role of marine-derived substances in modern medicine, emphasizing their importance in the ongoing battle against infectious diseases. Full article

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. Full article