Calcium phosphate nanoparticles conjugated with outer membrane vesicle of Riemerella anatipestifer for vaccine development in ducklings.

Biodegradable calcium phosphate nanoparticles offer a viable substitute for traditional adjuvants such as aluminum in vaccine production. Calcium phosphate nanoparticle adjuvanted with outer membrane vesicle (OMV) of gram negative bacteria may induce efficient immune response in the host. The present study was carried out to evaluate the potential of a mucosal vaccine formulation of calcium phosphate (CAP) nanoparticle using OMV of Riemerella anatipestifer (RA) as antigen against New Duck disease in ducks. The work was initiated with isolation, identification of RA, followed by OMV production and extraction. The CAP-OMV nanoparticle was prepared and characterized. The efficacy of the vaccine formulation and toxicity were studied in ducks. The average OMV yield in terms of protein concentration was found to be 122.33 ± 3.48 mg per liter of BHI broth. In SDS-PAGE, isolated OMVs exhibited presence of 16 distinct protein bands with molecular weight ranging from 142.1 to 12.1 kDa. Seven protein bands of 74.1, 69.3, 55.5, 50.6, 45.6, 25.1 and 13.1 kDa were detected relatively more distinct. The major bands detected in our findings were 42 kDa, 37 kDa and 16 kDa that corresponds to OmpA, OmpH, P6 respectively. The mean zeta size (±SD) and potential of the nanoparticle were 246.20 ± 0.53 nm and -25.60 ± 5.97 respectively. In transmission electron microscopy (TEM), the nanoparticles exhibited an average diameter of 129.80 ± 11.10 nm and displayed spherical morphology. The median protective dose (PD50) of CAP-OMV nanoparticle was 1881.10 µg of protein. Group I ducks received 3762 µg of protein (entrapped protein in CAP-OMV nanoparticle) via intra nasal route and it showed the highest serum IgG and secretory IgA level than other immunized groups. All experimental ducks were challenged with 10 × LD50 on 35 days of post primary immunization. Group I showed 100 % survivability in the challenge study. No gross and biochemical indication of acute or chronic toxicity were recorded. In conclusion, our results suggest that CAP-OMV nanoparticle can be a safe and efficient mucosal vaccine delivery system for RA, eliciting strong immune response in the host.

Genome-wide identification of antisense lncRNAs and their association with susceptibility to Flavobacterium psychrophilum in rainbow trout.

Eukaryotic genomes encode long noncoding natural antisense transcripts (lncNATs) that have been increasingly recognized as regulatory members of gene expression. Recently, we identified a few antisense transcripts correlating in expression with immune-related genes. However, a systematic genome-wide analysis of lncNATs in rainbow trout is lacking. This study used 134 RNA-Seq datasets from five different projects to identify antisense transcripts. A total of 13,503 lncNATs were identified genome-wide. About 75% of lncNATs showed multiple exons compared to 36.5% of the intergenic lncRNAs. RNA-Seq datasets from resistant, control, and susceptible rainbow trout genetic lines with significant differences in survival rate following Flavobacterium psychrophilum (Fp) infection were analyzed to investigate the potential role of the lncNATs during infection. Twenty-four pairwise comparisons between the different genetic lines, infectious status, and time points revealed 581 differentially expressed (DE) lncNATs and 179 differentially used exons (DUEs). Most of the DE lncNATs strongly and positively correlated in expression with their corresponding sense transcripts across 24 RNA-Seq datasets. LncNATs complementary to genes related to immunity, muscle contraction, proteolysis, and iron/heme metabolism were DE following infection. LncNATs complementary to hemolysis-related genes were DE in the resistant fish compared to susceptible fish on day 5 post-infection, suggesting enhanced clearance of free hemoglobin (Hb) and heme and increased erythropoiesis. LncNATs complementary to hepcidin, a master negative regulator of the plasma iron concentration, were the most downregulated lncNATs on day 5 of bacterial infection in the resistant fish. Ninety-four DE lncNAT, including five complementary to hepcidin, are located within 26 QTL regions previously identified in association with bacterial cold water disease (BCWD) in rainbow trout. Collectively, lncNATs are involved in the molecular architecture of fish immunity and should be further investigated for potential applications in genomic selection and genetic manipulation in aquaculture.

Efficacy of ulvan on immune response and immuno-antioxidant gene modulation in Labeo rohita against columnaris disease.

This study reports the effect of ulvan enriched diet on the influence of growth, changes in hemato-biochemical indices, improvement of antioxidant system, enhancement of innate-adaptive immunity and modification of immuno-antioxidant genes expression in Labeo rohita against Flavobacterium columnaris. The weight gain (WG) was significantly high (P > 0.05) in unchallenged normal and challenged fish fed with diets enriched with 25 and 50 mg kg-1 ulvan; the FCR was better (P > 0.05) when fed with 50 mg kg-1 enriched diet. In normal fish fed with or without ulvan supplementation was noted 100% survival rate (SR). In both groups, the red blood cell (RBC) and while blood cell (WBC) counts increased significantly (P > 0.05) when fed with 50 mg kg-1 ulvan diet whereas the hemoglobin (Hb) level increased significantly on being fed with 25 and 50 mg kg-1 ulvan diets. The SOD activity was enhanced significantly in both groups fed with any dose of ulvan diets whereas the MDA and GPx activity increased only with 25 and 50 mg kg-1 ulvan diets. The phagocytic (PC) activity significantly increased with any enriched diet and control diet groups while the respiratory burst (RB) activity increased only with 50 mg kg-1 ulvan diet. The alternate complement pathway (ACP), activity of lysozyme (Lyz), and immunoglobuline M (IgM) were better in both groups fed with 50 mg kg-1 ulvan diet. The SOD and GPx antioxidant gene expression were significantly high in both groups fed with any ulvan diet while the Nrf2 gene expression was high with 50 mg kg-1 ulvan diet. The IL-1ß, TNFα, hepcidin, Lyz, and IgM cytokines or proteins mRNA expression were significant in both groups fed with all ulvan supplement diet whereas the ß-2M expression was significant only with 50 mg kg-1 ulvan diet. The present research indicates that both L. rohita groups fed with 50 mg kg-1 ulvan diet significantly improved growth, antioxidant system, immune defense system, and immuno-antioxidant related gene expression against F. columnaris.

Impact of grape pomace flour (GPF) on immunity and immune-antioxidant-anti-inflammatory genes expression in Labeo rohita against Flavobacterium columnaris.

This study evaluates the effects of dietary inclusion of grape pomace flour (GPF) on growth, antioxidant, anti-inflammatory, innate-adaptive immunity, and immune genes expression in Labeo rohita against Flavobacterium columnaris. In both normal and challenged fish the growth rate, hematology and biochemical parameters significantly increased when fed with 200 and 300 mg GPF enriched diets; similarly the activities of antioxidants and innate-adaptive immune parameters, such as malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (GSH), phagocytic (PC), respiratory burst (RB), alternative pathway complement (ACP), lysozyme (Lyz), and total immunoglobulin M (IgM) significantly increased in both groups. Similarly, the immune, antioxidant, and anti-inflammatory-related gene mRNA expression was significantly up-regulated in head kidney (HK) tissues. The challenged fish fed without GPF always exhibited lower values of all the studied parameters. The results indicate that both normal and challenged fish treated with 200 mg GPF inclusion diet had significantly enhanced growth rate, antioxidant status, and immune defense mechanisms than with 300 mg GPF diet in L. rohita against F. columnaris.

The regulatory effects of pyridoxine deficiency on the grass carp (Ctenopharyngodon idella) gill barriers immunity, apoptosis, antioxidant, and tight junction challenged with Flavobacterium columnar.

The effects of dietary pyridoxine (PN) on the gill immunity, apoptosis, antioxidant and tight junction of grass cap (Ctenopharyngodon idella) were investigated in this study. Fish were fed semi-purified diets containing graded levels of PN for 10 weeks, and then challenged with Flavobacterium columnare by bath immersion exposure for 3 days. The results indicated that compared with the optimal PN level, PN deficiency resulted in a decline in the antimicrobial compound production of gill. In addition, PN deficiency up-regulated the pro-inflammatory cytokines and down-regulated the anti-inflammatory cytokines gene expression, which might be associated with the enhanced nuclear factor κB p65 and the inhibited target of rapamycin signalling pathways, respectively, suggesting that PN deficiency could impair gill immune barrier function. Furthermore, PN deficiency (1) induced cell apoptosis, which may be partly associated with the (apoptotic protease activating factor-1, Bcl-2 associated X protein)/caspase-9 and c-Rel/tumor necrosis factor α (rather than FasL)/caspase-8 mediated apoptosis pathway. (2) Inhibited Kelch-like ECH-associating protein 1a/NF-E2-related factor 2 mRNA expression, decreased the mRNA expression and activities of antioxidant enzymes, increased the levels of reactive oxygen species, protein carbonyl and malondialdehyde. (3) Increased the mRNA expression level of myosin light chain kinase, which may be result in the down-regulation of tight junction complexes such as zonula occludens 1, occludin and claudins (expect claudin-12 and claudin-15). These results suggest that PN deficiency could impair gill physical barrier function. In summary, dietary PN deficiency could cause the impairment of gill barrier function associated with immunity, apoptosis, antioxidant and tight junction, which may result in the increased the susceptibility of fish to pathogenic bacteria. Moreover, based on the gill rot morbidity, LZ activity and MDA content, the dietary PN requirements for grass cap were estimated to be 4.85, 4.78 and 4.77 mg kg-1 diet, respectively.

Administration of dietary recombinant hepcidin on grass carp (Ctenopharyngodon idella) against Flavobacterium columnare infection under cage aquaculture conditions.

Hepcidin links iron metabolism with innate immunity during the inhibition of bacterial infection. Our previous studies had shown that recombinant hepcidin can significantly reduce the mortality rate of Ctenopharyngodon idella infected with Flavobacterium columnare under laboratory conditions. Here, we studied the preventive and therapeutic effects of feed supplemented with different doses of recombinant hepcidin on F. columnare-challenged C. idella reared in a cage culture environment. The results showed that in the prevention groups, 30 and 90 mg/kg of added purified and unpurified hepcidin respectively resulted in a higher survival rate in the early post-infection period, while 60 mg/kg of purified hepcidin significantly improved the survival rate in the therapy group (all compared to the control group). In the hepatopancreas, the expression of hepcidin and ferritin was significantly up-regulated, and the levels of ferroportin and serum iron were significantly decreased, especially in the therapy group. In addition, the expression of iron-related genes in spleen and intestine exhibited a similar trend to that in hepatopancreas. Meanwhile, immune genes were up-regulated to varying degrees, and the therapy group exhibited a significantly improved expression of pro-inflammatory cytokines and specific immunity. In summary, our study shows that different doses of recombinant hepcidin had protective effects against bacterial infection by regulating the iron distribution and immune gene expression, which provides a strong foundation for the application of recombinant hepcidin in aquaculture.

Dietary Glycyrrhiza uralensis extracts supplementation elevated growth performance, immune responses and disease resistance against Flavobacterium columnare in yellow catfish (Pelteobagrus fulvidraco).

The present study was conducted to evaluate the influence of Glycyrrhiza uralensis (G. uralensis) extracts on the growth performance, histological structure, immune response and disease resistance against Flavobacterium columnare (F. columnare) of yellow catfish. Fish were fed with two different diets, i.e., basal diet as control group (CG) and diet containing G. uralensis extracts as experimental group (GG). After 60 days feeding, growth performance of GG fish was significantly improved, with increased WG and SGR but decreased FCR compared to CG fish. Fish were then challenged with F. columnare for two times, as fish showed rare mortality after the first infection. GG fish showed significantly lower cumulative mortality during F. cloumnare infection than CG fish after 21 days infection (dpi). Epithelial cell exfoliation and obvious cellular vacuolization in the skin and congestion of gill lamellae were detected in CG fish, while GG fish showed increased width of epidermis and mucous cells number in skin, and increased length of secondary lamina in gill. GG fish also exhibited higher enzyme activity of lysozyme in serum and mRNA expression of lysozyme in head kidney than CG fish at most time points post infection. G. uralensis extracts supplementation also induced earlier serum anti-oxidative responses, with increased superoxide dismutase activity and total antioxidant capacity in GG fish at 1 dpi. Compared to CG fish, GG fish showed increased expression level of genes involved in TLRs-NFκB signaling (TLR2, TLR3, TLR5, TLR9, Myd88, and p65NFκB), resulting in higher expression levels of pro-inflammatory cytokines (IL-1ß and IL-8) in the head kidney post infection. However, these genes showed deviation in the gill of GG fish, which increased at some time points but decreased at other time points. Moreover, G. uralensis extracts supplementation also significantly unregulated the expression levels of IgM and IgD in head kidney, and the expression levels of IgM in the gill of yellow catfish, suggesting the elevated humoral immune response during F. columnare infection. All these results contributed to the elevated disease resistance ability against F. cloumnare infection of yellow catfish after dietary G. uralensis extracts supplementation.

Erythromycin and florfenicol treatment of rainbow trout Oncorhynchus mykiss (Walbaum) experimentally infected with Flavobacterium psychrophilum.

Flavobacterium psychrophilum is responsible for significant economic losses in rainbow trout aquaculture. Antimicrobial treatment remains the primary means of control; however, there are limited choices available for use. The objectives of the study were therefore to determine the minimum inhibitory concentrations for erythromycin and florfenicol in selected F. psychrophilum isolates and to evaluate their clinical treatment efficacy in experimentally infected rainbow trout. All isolates tested had moderate susceptibility to florfenicol and erythromycin except one isolate, which had low susceptibility to erythromycin. Two isolates (one with moderate and one with low susceptibility to erythromycin) were used in an experimental infection trial. Rainbow trout juveniles were injected intraperitoneally with 108 cfu/fish and after mortality had begun, fish were given erythromycin- and florfenicol-medicated feed at a rate of 75 mg kg- 1 day- 1 and 10 mg kg- 1  day- 1 fish body weight, respectively, for 10 consecutive days. The splenic F. psychrophilum load was determined using an rpoC quantitative PCR throughout the 30-day trial. Relative to antibiotic-free controls, erythromycin treatment significantly (p < 0.05) reduced mortality of rainbow trout juveniles infected with FPG101, even when treatment was initiated after clinical signs developed.

Efficacy and safety of a non-mineral oil adjuvanted injectable vaccine for the protection of Atlantic salmon (Salmo salar L.) against Flavobacterium psychrophilum.

Flavobacterium psychrophilum is the causative agent of Rainbow Trout Fry Syndrome which has had a major impact on global salmonid aquaculture. Recent outbreaks in Atlantic salmon in Scotland and Chile have added to the need for a vaccine to protect both salmon and trout. At present no licensed vaccines are available in Europe, leaving antibiotics as the only course of action to contain disease outbreaks. Outbreaks generally occur in fry at temperatures between 10 and 15 °C. Recently outbreaks in larger fish have given added impetus to the development of a vaccine which can provide long term protection from this highly heterogeneous pathogen. Most fish injectable vaccines are formulated with oil emulsion adjuvants to induce strong and long lasting immunity, but which are known to cause side effects. Alternative adjuvants are currently sought to minimise these adverse effects. The current study was performed to assess the efficacy of a polyvalent, whole cell vaccine containing formalin-inactivated F. psychrophilum to induce protective immunity in Atlantic salmon. The vaccine was formulated with an adjuvant containing squalene and aluminium hydroxide, and was compared to a vaccine formulated with a traditional oil adjuvant, Montanide ISA 760VG, and a non-adjuvanted vaccine. Duplicate groups of salmon (23.5 ± 6.8 g) were vaccinated with each of the vaccine formulations or phosphate buffered saline by intraperitoneal injection. Fish were challenged by intramuscular injection with F. psychrophilum six weeks post-vaccination to test the efficacy of the vaccines. Cumulative mortality reached 70% in the control salmon, while the groups of salmon that received vaccine had significantly lower mortality than the controls (p = 0.0001), with no significant difference in survival between vaccinated groups. The squalene/alum adjuvant was safe, more readily metabolised by the fish and induced less histopathological changes than the traditional oil adjuvant.

Riemerella anatipestifer AS87_RS09170 gene is responsible for biotin synthesis, bacterial morphology and virulence.

Riemerella anatipestifer is a bacterial pathogen responsible for major economic losses within the duck industry. Recent studies have revealed that biotin biosynthesis is critical for the bacterium's survival and virulence. We previously found that R. anatipestifer AS87_RS09170, a putative bioF gene, is important for bacterial virulence. In the present study, we characterized the AS87_RS09170 gene in R. anatipestifer strain Yb2. Sequence analysis indicated that the AS87_RS09170 gene is highly conserved among R. anatipestifer strains; the deduced protein harbored the conserved pyridoxal 5'-phosphate binding pocket of 8-amino-7-oxononanoate synthase. Western blot analysis demonstrated that the biotin-dependent enzyme was present in smaller quantities in the mutant strain Yb2ΔbioF compared to that of the wide-type strain Yb2, suggesting that the biotin biosynthesis was defective. The mutant strain Yb2ΔbioF displayed a decreased growth rate at the exponential phase in tryptic soy broth culture and in BeaverBeads Streptavidin treated tryptic soy broth culture, but recovered when biotin was supplemented. In addition, the mutant strain Yb2ΔbioF showed an enhanced biofilm formation, as well as increased adhesion and invasion capacities to duck embryo fibroblasts. Moreover, the mutant strain Yb2ΔbioF exhibited irregular shapes with budding vegetations and relatively thickened cell walls under scanning and transmission electron microscope observation, as well as a reduced capacity to establish systemic infection in a duck infection model. These results provide the first evidence that the R. anatipestifer AS87_RS09170 gene is responsible for biotin synthesis, bacterial morphology and virulence.

Roles of B739_1343 in iron acquisition and pathogenesis in Riemerella anatipestifer CH-1 and evaluation of the RA-CH-1ΔB739_1343 mutant as an attenuated vaccine.

Iron is one of the most important elements for bacterial survival and pathogenicity. The iron uptake mechanism of Riemerella anatipestifer (R. anatipestifer, RA), a major pathogen that causes septicemia and polyserositis in ducks, is largely unknown. Here, the functions of the putative TonB-dependent iron transporter of RA-CH-1, B739_1343, in iron utilization and pathogenicity were investigated. Under iron-starved conditions, the mutant strain RA-CH-1ΔB739_1343 exhibited more seriously impaired growth than the wild-type strain RA-CH-1, and the expression of B739_1343 in the mutant strain restored growth. qRT-PCR results showed that the transcription of B739_1343 was not regulated by iron conditions. In an animal model, the median lethal dose (LD50) of the mutant strain RA-CH-1ΔB739_1343 increased more than 104-fold (1.6×1012 CFU) compared to that of the wild-type strain RA-CH-1 (1.43×108 CFU). In a duck co-infection model, the mutant strain RA-CH-1ΔB739_1343 was outcompeted by the wild-type RA-CH-1 in the blood, liver and brain of infected ducks, indicating that B739_1343 is a virulence factor of RA-CH-1. Finally, immunization with live bacteria of the mutant strain RA-CH-1ΔB739_1343 protected 83.33% of ducks against a high-dose (100-fold LD50) challenge with the wild-type strain RA-CH-1, suggesting that the mutant strain RA-CH-1ΔB739_1343 could be further developed as a potential live attenuated vaccine candidate for the duck industry.

Antibacterial Activity of Constituents from Mangosteen Garcinia mangostana Fruit Pericarp against Several Channel Catfish Pathogens.

Bacterial diseases cause major financial damage to the producers of Channel Catfish Ictalurus punctatus in the southeastern USA. The two most common bacterial diseases among pond-raised Channel Catfish are enteric septicemia of catfish, caused by the gram-negative bacterium Edwardsiella ictaluri, and columnaris disease, caused by the rod-shaped, gram-negative bacterium Flavobacterium columnare. Streptococcosis is another, less-common bacterial disease in catfish and is caused by the gram-positive coccus Streptococcus iniae. Catfish farmers typically rely on commercial antibiotics and other chemicals to prevent the economic damage from these diseases. Environmentally benign and efficacious alternatives to the currently used antibiotics and chemicals will tremendously help the catfish aquaculture industry. As part of our ongoing efforts in the search for such novel compounds, we investigated ethyl acetate and methanol extracts of mangosteen Garcinia mangostana fruit pericarp via bioassay-guided fractionation. Gamma-mangostin (γ-mangostin) was isolated and identified as the most promising active metabolite against F. columnare. One of the constituents in the mangosteen fruit pericarp, alpha-mangostin (α-mangostin), is the major xanthone; α-mangostin was found to be 10-fold less active than γ-mangostin when minimum inhibitory concentration values were compared.

Dietary threonine deficiency depressed the disease resistance, immune and physical barriers in the gills of juvenile grass carp (Ctenopharyngodon idella) under infection of Flavobacterium columnare.

This study was conducted to investigate the effects of dietary threonine on the disease resistance, gill immune and physical barriers function of juvenile grass carp (Ctenopharyngodon idella). A total of 1080 juveniles were fed six iso-nitrogenous diets containing graded levels of threonine (3.99-21.66 g kg-1 diet) for 8 weeks, and then challenged with Flavobacterium columnare. Results showed that threonine deficiency (3.99 g kg-1 diet): (1) increased the gill rot morbidity after exposure to F. columnare; (2) attenuated the gill immune barrier function by decreasing antimicrobial substances production, up-regulating the mRNA levels of pro-inflammatory cytokines (except IL-12p40), and down-regulating the anti-inflammatory cytokines partly due to the modulation of NF-κB and TOR signaling. (3) disrupt the gill tight junction complexes by down-regulating TJs (claudin-3, -b, -c, 12, occludin, ZO-1 and ZO-2) and up-regulating TJs (claudin-7a, -7b) as well as related signaling molecule myosin light chain kinase mRNA levels (P < 0.05). (4) exacerbated the gill apoptosis by up-regulating cysteinyl aspartic acid-protease-3, 8, 9, c-Jun N-terminal kinases and mediating apoptosis related factors mRNA levels (P < 0.05); (5) exacerbated oxidative injury with increased reactive oxygen species, malondialdehyde and protein carbonyl contents (P < 0.05), decreased the antioxidant related enzymes activities and corresponding mRNA levels (except glutathione peroxidase-1b and glutathione-S-transferase-omega 2) as well as glutathione contents (P < 0.05) partly ascribe to the abridgement of NF-E2-related factor 2 signaling [Nrf2/Keap1a (not Keap1b)] in fish gill. Overall, threonine deficiency depressed the disease resistance, and impaired immune and physical barriers in fish gill. Finally, based on the gill rot morbidity and biochemical indices (immune indices LA activity and antioxidant indices MDA content), threonine requirements for juvenile grass carp (9.53-53.43 g) were estimated to be 15.32 g kg-1 diet (4.73 g 100 g-1 protein), 15.52 g kg-1 diet (4.79 g 100 g-1 protein), 15.46 g kg-1 diet (4.77 g 100 g-1 protein), respectively.

Dietary vitamin C deficiency depressed the gill physical barriers and immune barriers referring to Nrf2, apoptosis, MLCK, NF-κB and TOR signaling in grass carp (Ctenopharyngodon idella) under infection of Flavobacterium columnare.

This study explored the effects of vitamin C on the physical barriers and immune barriers, and relative mRNA levels of signaling molecules in the gill of grass carp (Ctenopharyngodon idella) under infection of Flavobacterium columnare. The results indicated that compared with optimal vitamin C supplementation, vitamin C deficiency (2.9 mg/kg diet) (1) increased reactive oxygen species, malondialdehyde and protein carbonyl (PC) contents (P < 0.05), decreased the copper/zinc superoxide dismutase, manganese superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities and mRNA levels (P < 0.05), and glutathione and vitamin C contents (P < 0.05), down-regulated NF-E2-related factor 2 mRNA level (P < 0.05), and up-regulated Kelch-like ECH-associating protein (Keap) 1a (rather than Keap1b) mRNA level (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency induced oxidative injury in fish gill; (2) up-regulated caspase-3, -7, -8, -9, Fas ligand, B-cell lymphoma protein 2 associated X protein, apoptotic protease activating factor-1 mRNA levels (P < 0.05), and down-regulated inhibitor of apoptosis protein and B-cell lymphoma-2 (rather than myeloid cell leukemia-1) mRNA level (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency aggravated cell apoptosis in fish gill; (3) up-regulated pore-forming TJs Claudin-12, 15a, -15b, and related signaling molecules myosin light chain kinase, p38 mitogen-activated protein kinase (rather than c-Jun N-terminal kinases) mRNA levels (P < 0.05), and down-regulated barrier-forming TJs Occludin, zonula occludens (ZO) 1, ZO-2, Claudin-c, -3c, -7a, -7b mRNA levels (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency disrupted tight junctional complexes in fish gill; (4) decreased lysozyme and acid phosphatase (ACP) activities, and complement 3 (C3), C4 and IgM contents (P < 0.05), down-regulated the mRNA levels of antimicrobial peptides liver expressed antimicrobial peptide (LEAP) 2A, LEAP-2B, Hepcidin, ß-defensin mRNA levels (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency decrease fish gill immune function; (5) down-regulated the mRNA levels of anti-inflammatory cytokines-related factors interleukin 10 (IL-10), IL-11, transforming growth factor (TGF) ß1, TGF-ß2, inhibitor of κBa and eIF4E-binding protein 1 (4E-BP1) (rather than 4E-BP2) (P < 0.05), and up-regulated pro-inflammatory cytokines-related factors interferon γ2, IL-1ß, IL-6, IL-8, IL-12 P35, IL-12 P40, nuclear factor κB (NF-κB) p65 (rather than NF-κB p52), IκB kinases (IKK) (only IKKα and IKKγ), target of rapamycin and ribosomal protein S6 kinase 1 mRNA levels (P < 0.05) in the gill of grass carp under infection of F. columnare, suggesting that vitamin C deficiency aggravated fish gill inflammation. In conclusion, vitamin C deficiency disrupted physical barriers and immune barriers, and regulated relative mRNA levels of signaling molecules in fish gill. The vitamin C requirement for against gill rot morbidity of grass carp (264-1031 g) was estimated to be 156.0 mg/kg diet. In addition, based on the gill biochemical indices (antioxidant indices MDA, PC and vitamin C contents, and immune indices LA and ACP activity) the vitamin C requirements for grass carp (264-1031 g) were estimated to be 116.8, 156.6, 110.8, 57.8 and 134.9 mg/kg diet, respectively.

In vivo activity of cefquinome against Riemerella anatipestifer using the pericarditis model in the duck.

Cefquinome is a fourth-generation cephalosporin with broad-spectrum antibacterial activity, including activity against enteric gram-negative bacilli such as Riemerella anatipestifer. The pericarditis model was used to examine the pharmacodynamic characteristics of cefquinome against R. anatipestifer. Serum levels of cefquinome following the administration of different doses were determined by LC-MS/MS. Ducks with ca. 10(6) CFU/mL at the initiation of therapy were treated with cefquinome at doses that ranged from 0.0156 to 2 mg/kg of body weight/day (in 3, 6, 12, or 24 divided doses) for 24 h. The percentage of a 24-h dosing interval that the unbound serum cefquinome concentrations exceeded the MIC (fT > MIC) were the pharmacokinetic (PK)-pharmacodynamic (PD) parameter that best correlated with efficacy (R(2) 86.3% for R. anatipestifer, compared with 58.9% for the area under the concentration-time curve/MIC and 10.6% for peak/MIC). A sigmoid Emax model was used to estimate the magnitudes of the %fT > MIC associated with net bacterial stasis, a 1-log10 CFU reduction from baseline, and a 2-log10 CFU reduction from baseline; the corresponding values were (22.5 ± 1.3) %, (35.2 ± 4.5) %, and (42.4 ± 2.7) %. These data showed that treatment with cefquinome results in marked antibacterial effects in vivo against R. anatipestifer and that the host's immunity may also play a key role in the anti-infective therapy process.

Protective efficacy of Nigella sativa seeds and oil against columnaris disease in fishes.

Columnaris disease, caused by the bacterium Flavobacterium columnare, is currently the most frequently reported bacterial disease affecting farm-raised channel catfish in the USA. Common treatments against the disease include the use of medicated feed that has led to emergent antibiotic resistant strains of F. columnare. Nigella sativa (Black cumin) is a medicinal herb commonly used by many cultures as a natural remedy for numerous disorders. Recently, we have discovered the antibacterial activity of N. sativa and its oil extract against F. columnare. In this study, we showed N. sativa oil (NSO) strongly inhibited the growth of all of the strains of F. columnare tested and yielded significantly larger zones of inhibition than those produced by oxytetracyclin. We tested the protective effect against columnaris disease in vivo by incorporating NSO (5%) or N. sativa seeds (NSS) (5%) into fish feeds. Fishes (Ictalurus punctatus and Danio rerio) fed amended diets displayed significantly lower mortality than those fed control diets. Per cent mortalities in control groups ranged from 77% to 44% and from 70% to 18% in zebrafish and channel catfish, respectively. A dose study using different NSS concentrations showed that 5% NSS offered the most protection against columnaris disease in channel catfish.

Design, synthesis and antibacterial study of new potent and selective coumarin-chalcone derivatives for the treatment of tenacibaculosis.

With the aim of finding new chemical entities selective for fish pathogens to avoid drug resistance in humans, a series of coumarin-chalcone hybrid compounds with different patterns of substitution were designed and synthesized. Their antibacterial activity was evaluated against important types of human bacteria strains (Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa) and against a fourteen strains of the marine pathogen Tenacibaculum maritimum, responsible for tenacibaculosis in fish, which is an important disease that causes great economical loss in the aquaculture industry. All the amino derivatives 5-12 presented high activity against different strains of T. maritimum, no activity against any of the three human pathogenic bacteria strains and no toxicity. Compounds 6, 7 and 11 were the most promising molecules. The most sensitive strains to these compounds were LL01 8.3.8 and LL01 8.3.1, being compound 11 up to 20 times more active than enrofloxacin. Therefore these scaffolds are good candidates for aquaculture treatments, avoiding possible drug resistance problems in humans.

Antibacterial, anti-inflammatory, and antioxidant effects of Yinzhihuang injection.

The Yinzhihuang injection, a traditional Chinese medicine, has been the recent target of increasing interest due to its anti-inflammatory properties. The molecular basis by which Yinzhihuang injection could cure Riemerella anatipestifer (RA) serositis in ducks is unclear. This study evaluated the antibacterial, anti-inflammatory and antioxidant effects of Yinzhihuang injection, using disease models of RA-induced infectious serositis in ducks and heptane-induced inflammation in mice and rats. The duck mortality rate was reduced from 60% to 20% and both the inflammatory response and histological damage were ameliorated by treatment with Yinzhihuang injection (0.02 g/kg). Further studies indicated that superoxide dismutase (SOD), nitric oxide synthase (NOS), and inducible nitric oxide synthase (iNOS) were elevated while malondialdehyde (MDA), nitric oxide (NO) and RA growth were inhibited when the ducks were treated by Yinzhihuang injection. In addition, Yinzhihuang injection (0.04 g/ml) effectively inhibited xylene-induced auricle swelling in mice, (demonstrating an inhibition rate of 35.21%), egg albumen-induced paw metatarsus swelling in rats, (demonstrating an inhibition rate of 22.30%), and agar-induced formation of granulation tissue. These results suggest that Yinzhihuang injection ameliorates RA-induced infectious serositis in ducks by modulation of inflammatory mediators and antioxidation.

Impact of feed additives on surface mucosal health and columnaris susceptibility in channel catfish fingerlings, Ictalurus punctatus.

One of the highest priority areas for improvement in aquaculture is the development of dietary additives and formulations which provide for complete mucosal health and protection of fish raised in intensive systems. Far greater attention has been paid to dietary impact on gut health than to protective effects at other mucosal surfaces such as skin and gill. These exterior surfaces, however, are important primary targets for pathogen attachment and invasion. Flavobacterium columnare, the causative agent of columnaris disease, is among the most prevalent of all freshwater disease-causing bacteria, impacting global aquaculture of catfish, salmonids, baitfish and aquaria-trade species among others. This study evaluated whether the feeding of a standard catfish diet supplemented with Alltech dietary additives Actigen(®), a concentrated source of yeast cell wall-derived material and/or Allzyme(®) SSF, a fermented strain of Aspergillus niger, could offer protection against F. columnare mortality. A nine-week feeding trial of channel catfish fingerlings with basal diet (B), B + Allzyme(®) SSF, B + Actigen(®) and B + Actigen(®)+Allzyme(®) SSF revealed good growth in all conditions (FCR < 1.0), but no statistical differences in growth between the treatments were found. At nine weeks, based on pre-challenge trial results, basal, B + Actigen(®), and B + Allzyme(®) SSF groups of fish were selected for further challenges with F. columnare. Replicated challenge with a virulent F. columnare strain, revealed significantly longer median days to death in B + Allzyme(®) SSF and B + Actigen(®) when compared with the basal diet (P < 0.05) and significantly higher survival following the eight day challenge period in B + Actigen(®) when compared with the other two diets (P < 0.05). Given the superior protection provided by the B + Actigen(®) diet, we carried out transcriptomic comparison of gene expression of fish fed that diet and the basal diet before and after columnaris challenge using high-throughput RNA-seq. Pathway and enrichment analyses revealed changes in mannose receptor DEC205 and IL4 signaling at 0 h (prior to challenge) which likely explain a dramatic divergence in expression profiles between the two diets soon after pathogen challenge (8 h). Dietary mannose priming resulted in reduced expression of inflammatory cytokines, shifting response patterns instead to favor resolution and repair. Our results indicate that prebiotic dietary additives may provide protection extending beyond the gut to surface mucosa.