Vibrio Alginolyticus Research Articles

Phytochemical Constituents, Antimicrobial Properties and Bioactivity of Marine Red Seaweed (Kappaphycus alvarezii) and Seagrass (Cymodocea serrulata).

The present work was performed to evaluate the levels of phytochemical constituents and the antioxidant and antibacterial properties of marine red seaweed (Kappaphycus alvarezii) and seagrass (Cymodocea serrulata). Quantitative phytochemical analysis, antioxidant activity and antimicrobial activity against five potential pathogenic bacteria was investigated. In each case, we found the presence of flavonoids, tannins, phenolic compounds, glycosides, steroids, carbohydrates and ashes. Alkaloids were only found in K. alvarezii, though they were not found in C. serrulata. The antimicrobial properties of both K. alvarezii and C. serrulata chloroform extracts were found to be antagonistically effective against the Gram-positive bacteria Bacillus subtilis and the Gram-negative bacteria Vibrio parahaemolyticus, Vibrio alginolyticus, Vibrio harveyi and Klebsiella pneumoniae. GC-MS analysis revealed the presence of 94 bioactive compounds in K. alvarezii and 104 bioactive compounds in C. serrulata, including phenol, decane, dodecane, hexadecane, vanillin, heptadecane, diphenylamine, benzophenone, octadecanoic acid, dotriaconate, benzene, phytol, butanoic acid and 2-hydroxyl-ethyl ether, which all played important roles in antioxidant and antibacterial activities. Thus, in view of the results, both K. alvarezii and C. serrulata could be considered to be sources of ingredients with appreciable nutritional and medicinal value.

Multiplexed microfluidic screening of bacterial chemotaxis.

Microorganism sensing of and responding to ambient chemical gradients regulates a myriad of microbial processes that are fundamental to ecosystem function and human health and disease. The development of efficient, high-throughput screening tools for microbial chemotaxis is essential to disentangling the roles of diverse chemical compounds and concentrations that control cell nutrient uptake, chemorepulsion from toxins, and microbial pathogenesis. Here, we present a novel microfluidic multiplexed chemotaxis device (MCD) which uses serial dilution to simultaneously perform six parallel bacterial chemotaxis assays that span five orders of magnitude in chemostimulant concentration on a single chip. We first validated the dilution and gradient generation performance of the MCD, and then compared the measured chemotactic response of an established bacterial chemotaxis system (Vibrio alginolyticus) to a standard microfluidic assay. Next, the MCD's versatility was assessed by quantifying the chemotactic responses of different bacteria (Psuedoalteromonas haloplanktis, Escherichia coli) to different chemoattractants and chemorepellents. The MCD vastly accelerates the chemotactic screening process, which is critical to deciphering the complex sea of chemical stimuli underlying microbial responses.

Integration of microbiome and Koch’s postulates to reveal multiple bacterial pathogens of whitish muscle syndrome in mud crab, Scylla paramamosain

BackgroundFor more than a century, the Koch’s postulates have been the golden rule for determining the causative agents in diseases. However, in cases of multiple pathogens-one disease, in which different pathogens can cause the same disease, the selection of microorganisms that regress infection is hard when Koch’s postulates are applied. Microbiome approaches can obtain relatively complete information about disease-related microorganisms and can guide the selection of target microorganisms for regression infection. In the present study, whitish muscle syndrome (WMS) of Scylla paramamosain, which has typical symptoms with whitish muscle and blackened hemolymph was used as an example to establish a new research strategy that integrates microbiome approaches and Koch’s postulates to determinate causative agents of multiple pathogens-one disease.ResultsMicrobiome results revealed that Aeromonas, Acinetobacter, Shewanella, Chryseomicrobium, Exiguobacterium, Vibrio and Flavobacterium, and Kurtzmaniella in hemolymph were bacterial and fungal indicators for WMS. A total of 23 bacteria and 14 fungi were isolated from hemolymph and muscle tissues, and among the bacteria, Shewanella chilikensis, S. xiamenensis, Vibrio alginolyticus, S. putrefaciens, V. fluvialis, and V. parahaemolyticus were present in hemolymph and/or muscle tissues in each WMS crab, and the last three species were also present in three Healthy crabs. The target bacteria and fungi were further screened to regression infections based on two criteria: whether they belonged to the indicator genera for WMS, whether they were isolated from both hemolymph and muscle tissues in most WMS crabs. Only S. chilikensis, S. putrefaciens, S. xiamenensis, V. alginolyticus, V. fluvialis, and V. parahaemolyticus met both two criteria. The six bacteria that met both two criteria and six fungi and another bacterium that unmatched any of two criteria were used to perform regression infection experiments based on Koch’s postulates. S. chilikensis, S. putrefaciens, S. xiamenensis, V. alginolyticus, V. fluvialis, and V. parahaemolyticus met both two criteria, and the results indicate that they cause WMS in crabs independently.ConclusionsThis study fully demonstrated that our research strategy that integrates the microbiome and Koch’s postulates can maximize the ability to catch pathogens in one net for the situation of multiple pathogens-one disease.EgKJnBsvf5xgzELdpRDt_QVideo

Bacterial composition and antibiotic resistome profile of water in the Manila Bay South Harbor

Anthropogenic activities in Manila Bay, the oldest and busiest international port in the Philippines, may cause changes in flora and fauna within its harbors. Specifically, the ballasting and deballasting of ships may accidentally introduce new populations of microorganisms, plants, and animals. Ballasting (and deballasting), or the process of carrying in/out of seawater from ship tanks in major ports/harbors, are causing major disturbances, particularly in marine ecosystems. Previous studies have shown that marine microorganisms comprise 98% of the primary production and regulation of the ocean's biogeochemical processes. However, with the continuous community disturbances due to human influence, potential marine bacterial populations with antibiotic resistomes may occur, and impact marine diversity. Since data on the microbial communities in Manila Bay South Harbor are limited, this study determined the bacterial composition and antibiotic resistome profiles of water samples from the area. Next-generation sequencing techniques and culture-based methods were utilized to elucidate the bacterial and functional diversity, as well as the antibiotic resistome of the water samples from the Manila Bay South Harbor. The bacterial diversity of the water sample was made up primarily of members of Bacteroidetes, Firmicutes, and Prevotella. The Clusters of Orthologous Group (COG) Level 1 identified metabolism as the most dominant functional predicted metagenome. The characterization of antibiotic resistance genes (ARGs) from water samples revealed that ARGs encoding resistance to multidrug was the most abundant. On the other hand, the identified antibiotic-resistant bacteria included ampicillin-resistant Escherichia coli, multidrug-resistant Klebsiella pneumoniae, ampicillin- and cefuroxime-resistant Vibrio alginolyticus and ampicillin resistant Vibrio furnissii. The above results provide a baseline marine bacterial community and antibiotic resistome profile of the Manila Bay South Harbor. This information is critical in gaining a better understanding of the potential roles of shifts in marine microbiomes, and in turn, help in developing appropriate solutions for managing the undesirable consequences of ballast water.

Bacterial Co-Infection as a Potential Threat to Farmed Flathead Grey Mullet (Mugil cephalus): Phenotypic and Molecular Diagnosis, Histopathology, Immunity Response, and In Vitro Antibacterial Evaluation

Vibrio alginolyticus, Vibrio chlorea, and Enterococcus cloacae were the main bacterial pathogens investigated during recurrent episodes of mortalities among farmed flathead grey mullet (Mugil cephalus) in the Bahar El-Baqar area, Sharqia governorate, Egypt, during the summer season in 2021. Nevertheless, the contamination of water with heavy metals was evaluated. In this study, a total number of sixty moribund and freshly dead Mugil cephalus were examined clinically and upon post-mortem. Then, the bacterial isolates were subjected to bacteriological phenotypic examination, 16S rRNA gene sequencing, and antibiotic sensitivity testing. Histopathological screening and the immunity response of naturally infected M. cephalus were also implemented. In areas where bacterial strains were recovered in a high percentage, water contamination with Cu, Fe, and Ni was higher than the permissible limit. The results showed a high similarity (99–100%) to Vibrio and E. cloacae strains using phylogenetic analysis of 16S rRNA. Most isolates exhibited sensitivity to florfenicol, ciprofloxacin, and norfloxacin, while they were resistant to erythromycin and amoxicillin. Hemorrhage, oedema, hemosiderosis, and melanomacrophage activation in most affected tissues of infected M. cephalus were detected by light microscopy. Nevertheless, higher levels of AST and ALT, as well as serum inflammatory markers, CRP, and lysozyme activity, were shown in infected fish. There were higher MDA levels, along with a reduction of GSH, SOD, and catalase, in the gills and brain of infected M. cephalus, compared to the control fish. Our obtained data confirmed the high prevalence of Vibrio serovars and E. cloacae in infected grey mullets, describing their histopathological alterations, higher inflammatory response, and oxidative stress impact. These results could be useful indicators for understanding the pathogenesis of these pathogens in correlation with water parameter deterioration. Thus, the emergence of Vibrio and E. cloacae species in this study threatens the brackish water aquaculture industry in Egypt and poses a public health concern.

Isolation and Identification of Moderately Halophilic Bacteria from Soak Liquor Samples Collected of Leather Tanneries

Isolation and identification of protease and lipase producing moderately halophilic bacteria from soak liquor samples and studying their adverse effects to the sheepskin using scanning electron microscopy may provide critical data on decomposition of raw hide/skin materials during soaking process. Moreover, enzyme-production properties of the moderately halophilic isolates (such as catalase, oxidase, lipase, protease, urease, caseinase, amylase, cellulase, pullulanase, xylanase) were determined. The effects of different NaCl concentrations, pH and temperature values on the growth of moderately halophilic bacterial isolates were tested. In the present study, four moderately halophilic bacterial isolates were isolated and selected for further experiments. The isolated species designated as SLMHB5, SLMHB10, SLMHB12, SLMHB13 were similar to Vibrio alginolyticus, Terribacillus halophilus, Vibrio alginolyticus, and Vibrio parahaemolyticus species, respectively. Scanning electron micrographs of sheepskin samples demonstrated that enzymatic activities of moderately halophilic bacteria isolated from soak liquor samples which decomposed the skin structure. After 35-days storage period, the sheepskin sample showed bad odor, sticky appearance and hair slip. Hence, it is recommended to control these microorganisms during the soaking process with an effective antimicrobial agent.

Effect of Clostridium butyricum on intestinal microbiota and resistance to Vibrio alginolyticus of Penaeus vannamei

In order to evaluate the effect of Clostridium butyricum (C. butyricum) feeding on intestinal microorganisms and protection against infection by Vibrio alginolyticus (V. alginolyticus) in Penaeus vannamei (P. vannamei). We set up two groups, CG30 (fed normal feed) and CB30 (fed feed supplemented with C. butyricum), for the 30d C. butyricum feeding test, and four groups, CG (CG30 group injected with PBS), CB (CB30 group injected with PBS), VACG (CG30 group injected with V. alginolyticus), and VACB (CB30 group injected with V. alginolyticus), for the 24 h infection test. The protective effect of C. butyricum against acute V. alginolyticus infection in P. vannamei was explained in terms of survival, histopathology, changes in enzyme activity, transcriptome analysis, and immune-related genes. We found that feeding C. butyricum significantly altered intestinal microbial populations' abundance and significantly reduced Vibrio spp. In the V. alginolyticus stress test, C. butyricum improved the survival rate and alleviated pathological changes in hepatopancreatic tissues, alleviated the reduction of superoxide dismutase (SOD) and phenoloxidase (PO) activity caused by infection, and increased the lysozyme content in P. vannamei. VACB group compared with the VACG group, 1730 up-regulated differentially expressed genes (DEGs) and 2029 down-regulated DEGs were screened. Quantitative real-time PCR (qRT-PCR) showed that dietary supplementation with C. butyricum suppressed the upregulation of alkaline phosphatase (AKP) transcription factors and the downregulation of prophenoloxidase (proPO), alpha-2-macroglobulin (A2M), and anti-lipopolysaccharide factor (ALF) induced by V. alginolyticus infection. In conclusion, feed supplementation with C. butyricum changed P. vannamei's population ratio of intestinal microorganisms. Moreover, C. butyricum has the potential to act as an inhibitor of V. alginolyticus infection and enhance the resistance of P. vannamei to V. alginolyticus infection.

Characterization of a Filamentous Phage, Vaf1, from Vibrio alginolyticus AP-1.

Filamentous phages are ubiquitously distributed in the global oceans. However, little is known about their biological contribution to their host's genetic and phenotypic diversity. In this study, a filamentous phage, Vaf1, was isolated and characterized from the emerging marine pathogen strain Vibrio alginolyticus AP-1. We explored the effects of the resident phage Vaf1 on the host physiology under diverse conditions by precisely deleting the entire phage Vaf1. Our results demonstrate that the presence of phage Vaf1 significantly increased biofilm formation, swarming motility, and contact-dependent competition. Furthermore, the gene expression profile suggests that several phage genes were upregulated in response to low-nutrient conditions. Unexpectedly, an in vivo study of zebrafish shows that fish infected with strain ΔVaf1 survived longer than those infected with wild-type strain AP-1, indicating that Vaf1 contributes to the virulence of V. alginolyticus. Together, our results provide direct evidence for the effect of Vaf1 phage-mediated phenotypic changes in marine bacteria V. alginolyticus. This further emphasizes the impressive complexity and diversity that filamentous phage-host interactions pose and the challenges associated with bacterial disease control in marine aquaculture. IMPORTANCE Non-lytic filamentous phages can replicate without killing their host, establishing long-term persistence within the bacterial host. In contrast to the well-studied CTXφ phage of the human-pathogenic Vibrio cholerae, little is known about the filamentous phage Vaf1 and its biological role in host fitness. In this study, we constructed a filamentous phage-deleted strain, ΔVaf1, and provided direct evidence on how an intact phage, φVaf1, belonging to the family Inoviridae, helps the bacterial host AP-1 to overcome adverse environmental conditions. Our results likely open new avenues for fundamental studies on how filamentous phage-host interactions regulate different aspects of Vibrio cell behaviors.

“Antibiotic Resistance in the Vibrio species isolated from the estuarine sediments of Uttara Kannada Karnataka”

Vibrio species are the marine pathogenic bacterium which causes the health issues in the infected organisms. Antibiotic resistance in the Vibrio species is the threat to the human health by the transfer of the resistant gene in the human from the food chain. The present study was carried out to isolate the Vibrio species and to study antibiotic resistance from the sediments of two estuaries Kali and Aghanashini from Uttara Kannada, Karnataka. The sampling was done during low tide for the period of ten months from September 2021 to June 2022. The total vibrio count was observed in range between 3.86 to 4.83 Log X101 CFU/g. Vibrio parahaemolyticus, Vibrio alginolyticus, Vibrio navarrensis and Vibrio vulnificus were isolated and identified from the sediments. The identified Vibrio species were resistant to ampicillin and sensitive to chloramphenicol and tetracycline. Due the over use of antibiotics in the aquaculture and mariculture activities there is a possibility of organism to show multiple resistance towards the antibiotics.

Suboptimal environmental conditions prolong phage epidemics in bacterial populations.

Infections by filamentous phages, which are usually nonlethal to the bacterial cells, influence bacterial fitness in various ways. While phage-encoded accessory genes, for example virulence genes, can be highly beneficial, the production of viral particles is energetically costly and often reduces bacterial growth. Consequently, if costs outweigh benefits, bacteria evolve resistance, which can shorten phage epidemics. Abiotic conditions are known to influence the net-fitness effect for infected bacteria. Their impact on the dynamics and trajectories of host resistance evolution, however, remains yet unknown. To address this, we experimentally evolved the bacterium Vibrio alginolyticus in the presence of a filamentous phage at three different salinity levels, that is (1) ambient, (2) 50% reduction and (3) fluctuations between reduced and ambient. In all three salinities, bacteria rapidly acquired resistance through super infection exclusion (SIE), whereby phage-infected cells acquired immunity at the cost of reduced growth. Over time, SIE was gradually replaced by evolutionary fitter surface receptor mutants (SRM). This replacement was significantly faster at ambient and fluctuating conditions compared with the low saline environment. Our experimentally parameterized mathematical model explains that suboptimal environmental conditions, in which bacterial growth is slower, slow down phage resistance evolution ultimately prolonging phage epidemics. Our results may explain the high prevalence of filamentous phages in natural environments where bacteria are frequently exposed to suboptimal conditions and constantly shifting selections regimes. Thus, our future ocean may favour the emergence of phage-born pathogenic bacteria and impose a greater risk for disease outbreaks, impacting not only marine animals but also humans.

Naturally occurring beneficial bacteria Vibrio alginolyticus X-2 protects seaweed from bleaching disease.

Microbiome manipulation is gaining fresh attention as a way to mitigate diseases in aquaculture. The commercially farmed seaweed Saccharina japonica suffers from a bacterial-induced bleaching disease, which has major implications for the reliable supply of healthy sporelings. Here, we identify a beneficial bacterium, Vibrio alginolyticus X-2 that significantly reduces the risk of bleaching disease. By combining infection assays and multi-omic analyses, we provide evidence to suggest that the underlying protective mechanisms of V. alginolyticus X-2 involve maintaining epibacterial communities, increasing the gene expression of S. japonica related to immune and stress protection pathways, and stimulating betaine concentrations in S. japonica holobionts. Thus, V. alginolyticus X-2 can elicit a suite of microbial and host responses to mitigate the bleaching disease. Our study provides insights into disease control in farmed S. japonica through the application of beneficial bacteria. IMPORTANCE Beneficial bacteria can elicit a suite of microbial and host responses to enhance the resistance to bleaching disease.

Identification and characterization of mitogen-activated protein kinase kinase 4 (MKK4) from the mud crab Scylla paramamosain in response to Vibrio alginolyticus and White Spot Syndrome Virus (WSSV)

Mitogen-activated protein kinase kinase 4 (MKK4), serves as a critical component of the mitogen-activated protein kinase signaling pathway, facilitating the direct phosphorylation and activation of the c-Jun N-terminal kinase (JNK) and p38 families of MAP kinases in response to environmental stresses. In the current research, we identified two MKK4 subtypes, namely SpMKK4-1 and SpMKK4-2, from Scylla paramamosain, followed by the analysis of their molecular characteristics and tissue distributions. The expression of SpMKK4s was induced upon WSSV and Vibrio alginolyticus challenges, and the bacteria clearance capacity and antimicrobial peptide (AMP) genes’ expression upon bacterial infection were significantly decreased after knocking down SpMKK4s. Additionally, the overexpression of both SpMKK4s remarkably activated NF-κB reporter plasmid in HEK293T cells, suggesting the activation of the NF-κB signaling pathway. These results indicated the participation of SpMKK4s in the innate immunity of crabs, which shed light on a better understanding of the mechanisms through which MKK4s regulate innate immunity.

Evaluation of Antibacterial Activity of Selenium Nanoparticles against Food-Borne Pathogens.

Selenium is an essential micronutrient for all mammals and plays an important role in maintaining human physiological functions. Selenium nanoparticles (SeNPs) have been shown to demonstrate antioxidant and antimicrobial activity. The objective of this study was to explore whether SeNPs have the potential to be used as food preservatives with which to reduce food spoilage. SeNPs were synthesized through ascorbic acid reduction of sodium selenite (Na2SeO3) in the presence of bovine serum albumin (BSA) as a capping and stabilizing agent. The chemically synthesized SeNPs had a spherical conformation with an average diameter of 22.8 ± 4.7 nm. FTIR analysis confirmed that the nanoparticles were covered with BSA. We further tested the antibacterial activity of these SeNPs against ten common food-borne bacteria. A colony-forming unit assay showed that SeNPs exhibited inhibition on the growth of Listeria Monocytogens (ATCC15313) and Staphylococcus epidermidis (ATCC 700583) starting at 0.5 µg/mL, but higher concentrations were required to slow down the growth of Staphylococcus aureus (ATCC12600), Vibrio alginolyticus (ATCC 33787), and Salmonella enterica (ATCC19585). No inhibition was observed on the growth of the other five test bacteria in our study. Our data suggested that the chemically synthesized SeNPs were able to inhibit the growth of some food-borne bacteria. The size and shape of SeNPs, method of synthesis, and combination of SeNPs with other food preservatives should be considered when SeNPs are to be used for the prevention of bacteria-mediated food spoilage.

Transcriptome profiling explores the immune defence mechanism of triploid Pacific oyster (Crassostrea gigas) blood against Vibrio alginolyticus based on protein interaction networks.

Triploid oysters have provided the oyster industry with many benefits, such as fast growth rates, meat quality improvement, and increased oyster production and economic benefits, since the first report on triploid oysters was published. The development of polyploid technology has remarkably increased the output of triploid oysters to meet the increasing demand of consumers for Crassostrea gigas in the past decades. At present, research on triploid oyster has mainly focused on breeding and growth, but studies on the immunity of triploid oysters are limited. According to recent reports, Vibrio alginolyticus is a highly virulent strain that can cause disease and death in shellfish, shrimp, as well as serious economic losses. V. alginolyticus may be a reason why oysters die during summer. Therefore, using V. alginolyticus to explore the resistance and immune defense mechanisms of triploid oysters against pathogens presents practical significance. Transcriptome analysis of gene expression was performed in triploid C. gigas at 12 and 48h after infection with V. alginolyticus, and the respective 2257 and 191 differentially expressed genes (DEGs) were identified. The results of GO and KEGG enrichment analyses showed that multiple significantly enriched GO terms and KEGG signaling pathways are associated with immunity. A protein-protein interaction network was constructed to investigate the interaction relationship of immune-related genes. Finally, we verified the expression situation of 16 key genes using quantitative RT-PCR. This study is the first to use the PPI network in exploring the immune defense mechanism of triploid C. gigas blood to fill the gap in the immune mechanism of triploid oysters and other mollusks, and provide valuable reference for future triploid farming and pathogen prevention and control.

A REVIEW OF ANTIBACTERIAL POTENTIAL OF BANANG-BANANG PLANT (Xylocarpus granatum J.Koenig) EXTRACT

Background: Xylocarpus granatum has been used traditionally by coastal communities to treat various diseases. It is known that this plant contains secondary metabolites with various pharmacological activities, including as an antibacterial. Objective: This review article aims to provide information regarding the potential antibacterial activity of banang-banang plants and to summarize the content of compounds that have antibacterial properties and their mechanism of action. Methods: The preparation of this article is through literature studies from various international journals and national journals obtained online by taking into account predetermined inclusion and exclusion criteria. Then it was selected and studied further to obtain data related to the antibacterial activity of banang-banang plants and the content of secondary metabolites that have potential as antibacterials. Results: The banang-banang plant, especially the leaves, roots, fruit, seeds, fruit flesh, fruit peels, stems and bark with its secondary metabolites can inhibit several bacterial species such as Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli, Vibrio alginolyticus, Staphylococcus aureus, Shigella boydii , Proteus spp., Streptococcus pyogenes, Ralstonia solanacaerum, Propionibacterium acnes, Agrobacterium tumefaciens, Aspergillus paraciticus, Bacillus subtilis, Candida albicans, Pseudomonas fluorescence, Micrococcus luteus, Saccharomyces ceresiviae, Salmonella typhi, Vibrio alginoliticus and Aeromonas hydrophilla. The secondary metabolites of this plant that have potential as antibacterial are tannins, saponins, steroids, phenols, triterpenoids, flavonoids, alkaloids, terpenoids and glycosides which have their respective mechanisms of action as antibacterial agents. Conclusion: Secondary metabolites contained in each part of the Xylocarpus granatum plant are thought to have a role in its antibacterial activity.Keywords: Antibacterial, Mechanism of action, Secondary metabolite, Xylocarpus granatum J.Koenig.

Identification and evaluation of potential probiotics against skin-ulceration disease in the Chinese tongue sole (Cynoglossus semilaevis)

In this study, three highly pathogenic bacterial strains (Vibrio harveyi TB6, Vibrio alginolyticus TN1, and Vibrio parahaemolyticus TN3) were isolated from skin ulcers and intestines of diseased Chinese tongue sole (Cynoglossus semilaevis). The bacteria were investigated using hemolytic activity tests, in vitro co-culture with intestinal epithelial cells, and artificial infection of C. semilaevis. A further 126 strains were isolated from the intestines of healthy C. semilaevis. The three pathogens were used as indicator bacteria, and the antagonistic strains were identified from the 126 strains. The activities of exocrine digestive enzymes in the strains were also tested. Four strains with antibacterial and digestive enzyme activities were obtained and the best strains, Bacillus subtilis Y2 and Bacillus amyloliquefaciens Y9, were selected according to their ability to protect epithelial cells from infection. In addition, the effects of strains Y2 and Y9 at the individual level were investigated, finding that the activities of the immune-related enzymes superoxide dismutase, catalase, acid phosphatase, and peroxidase were significantly increased in the sera of the treatment group compared with the control group (p<0.05). The specific growth rate (SGR, %) was also increased, especially in the Y2 group, and was significantly higher compared with the controls (p<0.05). The result of the artificial infection test showed that the cumulative mortality within 72h in the Y2 group was the lowest (50.5%), and in the Y9 group (68.5%) it was significantly lower than that in the control group (100%) (p<0.05). Analysis of the intestinal microbial communities indicated that Y2 and Y9 could alter the composition of the intestinal flora, increasing both species richness and evenness, and inhibiting the growth of Vibrio in the intestine. These results suggested food supplemented with Y2 and Y9 could improve both immune function and disease resistance, as well as have a positive effect on the growth performance and the intestinal morphology of C. semilaevis.

Protective Effect of Willow (Salix babylonica L.) on Fish Resistance to Vibrio parahaemolyticus and Vibrio alginolyticus

Vibrio spp. cause vibriosis in many saltwater and freshwater aquatic species, such as fish, crustaceans, and mollusks. Vibrio parahaemolyticus and Vibrio alginolyticus are among the few Vibrio species commonly found in infections in fish. This study aimed at investigating the chemical composition and evaluating the antibacterial activities of Salix babylonica L. The ethyl acetate (LL2) and methanolic (LL3) extracts were used to evaluate the resistance of strains as V. parahaemolyticus LBT6 and VTCC 12233, and two strains of V. alginolyticus, NG20 and ATCC 17749, and compared their efficacy with cefotaxime in order to find an alternative to antibiotics in the treatment of vibriosis. The obtained results show that the LL2 extract, with its major components identified as chrysoeriol, luteolin, and β-sitosterol, exhibited a bacteriostatic effect against all the tested strains. In parallel, the LL3 extract, with the four major compounds luteolin-7-O-β-D-glucopyranoside, salicin, p-hydroxy benzoic acid, and β-sitosterol-3-O-β-D-glucopyranoside, showed significant bactericidal activity against these four strains; the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) varied from 2.0 to 3.0 μg/mL and from 3.5 to 5.0 μg/mL, respectively. Moreover, the LL3 extract could effectively increase the survival rate of the challenged fish at a dose of 5% (w/w) for the zebrafish (Danio rerio) and 3% (w/w) for the sea bass (Lates calcarifer). The LL3 extract showed a potential application of S. babylonica L. in the prevention and treatment of vibriosis in fish.

Distribution, Prevalence, and Antibiotic Susceptibility Profiles of Infectious Noncholera Vibrio Species in Malaysia.

The noncholera Vibrio spp. which cause vibriosis are abundantly found in our water ecosystem. These bacteria could negatively affect both humans and animals. To date, there is a paucity of information available on the existence and pathogenicity of this particular noncholera Vibrio spp. in Malaysia in comparison to their counterpart, Vibrio cholera. In this study, we extracted retrospective data from Malaysian surveillance database. Analysis was carried out using WHONET software focusing noncholera Vibrio spp. including Vibrio parahaemolyticus, Vibrio vulnificus, Vibrio fluvialis, Vibrio alginolyticus, Vibrio hollisae (Grimontia hollisae), Vibrio mimicus, Vibrio metschnikovii, and Vibrio furnissii. Here, we report the first distribution and prevalence of these species isolated in Malaysia together with the antibiotic sensitivity profile based on the species. We found that V. parahaemolyticus is the predominant species isolated in Malaysia. Noticeably, across the study period, V. fluvialis is becoming more prevalent, as compared to V. parahaemolyticus. In addition, this study also reports the first isolation of pathogenic V. furnissii from stool in Malaysia. These data represent an important step toward understanding the potential emergence of noncholera Vibrio spp. outbreaks.

Antibacterial Activity against Four Fish Pathogenic Bacteria of Twelve Microalgae Species Isolated from Lagoons in Western Greece.

Microalgae may produce a range of high-value bioactive substances, making them a promising resource for various applications. In this study, the antibacterial activity of twelve microalgae species isolated from lagoons in western Greece was examined against four fish pathogenic bacteria (Vibrio anguillarum, Aeromonas veronii, Vibrio alginolyticus, and Vibrio harveyi). Two experimental approaches were used to evaluate the inhibitory effect of microalgae on pathogenic bacteria. The first approach used bacteria-free microalgae cultures, whereas the second approach used filter-sterilized supernatant from centrifuged microalgae cultures. The results demonstrated that all microalgae had inhibitory effects against pathogenic bacteria in the first approach, particularly 4 days after inoculation, where Asteromonas gracilis and Tetraselmis sp. (red var., Pappas) exhibited the highest inhibitory activity, reducing bacterial growth by 1 to 3 log units. In the second approach, Tetraselmis sp. (red var., Pappas) showed significant inhibition against V. alginolyticus between 4 and 25 h after inoculation. Moreover, all tested cyanobacteria exhibited inhibitory activity against V. alginolyticus between 21 and 48 h after inoculation. Statistical analysis was performed using the independent samples t-test. These findings suggested that microalgae produce compounds with antibacterial activity, which could be useful in aquaculture.

Antimicrobial efficacy of composite irrigation solution against dominant pathogens in seawater immersion wound and in vivo wound healing assessment.

Seawater immersion wound is inevitably accompanied by bacterial infection. Effective irrigation is critical for bacterial infection prevention and wound healing. In this study, the antimicrobial efficacy of a designed composite irrigation solution against several dominant pathogens in seawater immersion wounds was evaluated, and in vivo wound healing assessment was conducted in a rat model. According to the time-kill result, the composite irrigation solution exhibits excellent and rapid bactericidal effect against Vibrio alginolyticus and Vibrio parahaemolyticus within 30 s of treatment while eliminating Candida albicans, Pseudomonas aeruginosa, Escherichia coli, and the mixed microbes after 1 h, 2 h, 6 h, and 12 h of treatment, respectively. Significant bacterial count reduction of Staphylococcus aureus was observed after 5 h treatment. In addition to its skin non-irritating attribute, the in vivo wound healing results further demonstrated that the irrigation solution showed high repair efficiency in the skin defect model inoculated with the mixed microbes. The wound healing rate was significantly higher than that of the control and normal saline groups. It could also effectively reduce the number of viable bacteria on the wound surface. The histological staining indicated that the irrigation solution could reduce inflammatory cells and promote collagen fibers and angiogenesis, thereby promoting wound healing. We believed that the designed composite irrigation solution has great potential for application in the treatment of seawater immersion wounds.