Immune Responses and Protective Immunity in Pangasius Pangasius (Hamilton, 1822) as Induced by Outer Membrane Proteins of Edwardsiella Tarda and Aluminium Hydroxide Adjuvant Complex

Edwardsiella tarda is considered one of the important bacterial fish pathogens. The outer membrane proteins (OMPs) of E. tarda are structurally and functionally conserved, and immunogenic. This study assessed the effects of the OMPs of E. tarda CGH9 as a vaccine without aluminium hydroxide [AH] (T1) and with AH adjuvant (T2) on the respiratory burst (ROB) activity, lymphocyte proliferation of head kidney (HK) leukocytes, and serum antibody production in pangas catfish Pangasius pangasius. The ROB activity and lymphocyte proliferation of HK leukocytes increased in both vaccinated groups compared to control. Nonetheless, the T2 group showed a gradual increase in ROB activity and lymphocyte proliferation of HK leukocytes up to 3-weeks post-vaccination (wpv). The serum antibody production in the T1 group decreased initially for up to 2-wpv and increased from 3-wpv; whereas, in the T2 group, the serum-specific antibody levels were significantly high from 1-wpv compared to control. Simultaneously, the protective efficacy in terms of relative percentage survival (RPS) in the T2 group after injecting with a lethal dose of E. tarda CGH9 was high (89.00±15.56) compared to the T1 group (78.00±0.00). Furthermore, the catfish administered with a booster dose of E. tarda OMPs with or without AH adjuvant showed no additional increase in immune response or protective immunity. These results suggested that E. tarda OMPs and AH adjuvant complex has a higher potential to induce protective immunity, which may be a good choice as a vaccine to combat E. tarda infection in catfish.

Isolation and Identification of major bacteria from three Ethiopian rift valley lakes live and processed fish, and water samples: Implications in sanitary system of fish products

Bacterial pathogens are a great threat to fish production. Gram-negative bacteria are among the major bacterial fish pathogens and zoonotic with the potential to infect humans. This cross-sectional study was conducted to isolate and identify major gram-negative bacteria from live and processed fish, and water samples from Lakes Hawassa, Langanoo and Ziway. A total of 674 different types of samples: 630 tissue samples (210 samples for each intestine, Kidney and liver collected from 210 live fish (Oreochromis niloticus, Cyprinus carpio and Clarias gariepinus), 20 processed fish samples from lake Ziway fish processing center and 24 lake water samples were included in the study from each lake. The mean values of pH, temperature, dissolved oxygen and nitrate in all water samples were within the normal range at which most freshwater fish species become non-stressed. Of a total of 674 samples included in the study, the bacteria were isolated from 154 (22.8%) samples with significant difference (P<0.05) observed in some isolates with respect to sample origin. Of these 154 isolates, 103(66.8%) isolates were gram-negative bacteria consisting of 15 species based on morphology and a range of biochemical tests. From live fish samples, Escherichia coli was the dominant species with 15 isolates followed by Edwardsiella tarda (12), Salmonella Paratyphi (10), Salmonella Typhi (9), Shigella dysenteriae(7), Shigella flexneri (7), Klebsiella pneumonia (7), Enterobacter aerogenes (6), Enterobacter cloacae (5), Pseudomonas aeruginosa (5), Vibrio parahemolyticus (5), Aeromonas sobria (4), Citrobacter freundii (4), Citrobacter koseri (4) and Plesiomonas shigelloides(3). Detection of common fecal coliforms (E. coli, K. pneumoniae and E. aerogenes) and Salmonella spp. in processed fish indicates the potential danger of passage of pathogenic bacteria and/or their poisons to humans via infected and/or contaminated fish products. Human infection by pathogenic fish bacteria and food poisoning is possible through contamination of fish product in fish production chain due to inadequate handling, poor hygiene and contact with contaminated water. Therefore, producers, consumers and all other stakeholders need to be cautious during handling, processing and consumption of fish harvested from the study lakes.

A Mini- review : Effect of Phyllantus niruri L. on Growth and Health of Fish

Phyllanthus niruri L. is one of the herbal ingredients that has been widely used to treat various diseases in humans such as intestinal infections, kidney stones, chronic liver disease, diabetes, hepatitis B, asthma, gonorrhea, bronchitis, syphilis and boost the immune system. The ability of P. niruri in overcoming various diseases is based on its phytochemical content and pharmacological properties. Based on these properties, the plant may possibly be used as a drug to treat diseases in fish. So the purpose of writing this article is to review the extent to which P. niruri can be used as an alternative medicine to treat disease and maintain fish health. Secondary metabolites and phyllanthine as specific compounds present in P. niruri have antibacterial effects for types of bacteria that usually attack fish such as Aeromonas hydrophila, Edwardsiella tarda, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa. In addition, it has the effect of being an antioxidant, immunostimulant and can be used for treatment and to increase fish growth. So it can be concluded that P. niruri can be used as an alternative material to maintain health and help fish growth.

Degradation of Crude Oil by Bacteria Isolated from Various Soil Plantation at Idanre, Nigeria

Degradation of crude oil by bacteria isolated from three plantations soil at Idanre, Nigeria were comparatively investigated. Soil samples collected by hand trowel at 5cm rhizosphere of Cocoa, Orange, and Teak plantations from Idanre, Ondo State. The crude oil – forcados blend was obtained from Warri, Delta State, Nigeria. Gram negative bacteria were isolated from rhizosphere soil sample using standard microbiological methods. Preparation of Biomass was done by centrifuging nutrient broth repeatedly to wash cells. Harvested cells were obtained for the degradation of crude oil. Harvested cells were inoculated with crude oil and then incubated in a shaker. Degradation of crude oil was monitored by using spectrophotometer to read the OD at 540 nm. The bacteria isolated from rhizosphere of cocoa include: Citrobacter freundii, Yersinia pestis, Edwardsiella tarda,. Serratia marcescens. Rhizosphere of orange; Providencia stuatii while Enterobacter agglumerans, Moellerella wisconsis were isolated from rhizosphere of teak. The most effective hydrocarbon utilizing bacteria was Enterobacter agglumerans, which resulted in increase in population densities and reduction in hydrocarbon contents in the crude oil. Findings from this study shows the effectiveness of degrading hydrocarbon in liquid medium and further confirmed the potency of bacterial cells to degrade crude oil.

Construction of Genomic Library and Screening of Edwardsiella tarda Immunogenic Proteins for Their Protective Efficacy Against Edwardsiellosis

Edwardsiella tarda is a severe aquaculture pathogen that can infect many hosts including humans, animals, and fish. Timely diagnosis and treatment are crucial for the control of edwardsiellosis in the aqua industry. By using rabbit polyclonal antibody, an expression gene library of virulent Edwardsiella tarda strain ED-BDU 1 isolated in south India was constructed and screened. The identified immune expressive proteins were characterized, and the corresponding coding sequences were cloned, expressed, and the purified recombinant proteins were used as antigens. The identified immunoreactive proteins namely HflC, HflK, and YhcI were studied for their immune protective potential in vivo by challenge experiments. The protective efficacy of HflC, HflK, and YhcI showed that the clearance of Edwardsiella from the host with ~ 60% survivability. Further, the immunoreactive proteins induce a strong immune response upon infection and elicit the significant production of IL-10, IFN-γ, Th1, and Th2 mediated mRNA expression and were therefore effective in vaccine production for edwardsiellosis.

Bacillus spp. Inhibit Edwardsiella tarda Quorum-Sensing and Fish Infection

The disruption of pathogen communication or quorum-sensing (QS) via quorum-quenching (QQ) molecules has been proposed as a promising strategy to fight bacterial infections. Bacillus spp. have recognizable biotechnology applications, namely as probiotic health-promoting agents or as a source of natural antimicrobial molecules, including QQ molecules. This study characterized the QQ potential of 200 Bacillus spp., isolated from the gut of different aquaculture fish species, to suppress fish pathogens QS. Approximately 12% of the tested Bacillus spp. fish isolates (FI). were able to interfere with synthetic QS molecules. Ten isolates were further selected as producers of extracellular QQ-molecules and their QQ capacity was evaluated against the QS of important aquaculture bacterial pathogens, namely Aeromonas spp., Vibrio spp., Photobacterium damselae, Edwardsiela tarda, and Shigella sonnei. The results revealed that A. veronii and E. tarda produce QS molecules that are detectable by the Chr. violaceum biosensor, and which were degraded when exposed to the extracellular extracts of three FI isolates. Moreover, the same isolates, identified as B. subtilis, B. vezelensis, and B. pumilus, significantly reduced the pathogenicity of E. tarda in zebrafish larvae, increasing its survival by 50%. Taken together, these results identified three Bacillus spp. capable of extracellularly quenching aquaculture pathogen communication, and thus become a promising source of bioactive molecules for use in the biocontrol of aquaculture bacterial diseases.

Transcriptome Analysis of Immune Response Process in Yellow Catfish (Pelteobagrus fulvidraco) During Edwardsiella tarda Exposure

Edwardsiella tarda, the causative agent of ascites disease, is a major fish pathogen and has caused significant economic losses in aquaculture. To decipher the immune response process challenged by E. tarda in yellow catfish (Pelteobagrus fulvidraco), the transcriptomic profiles of the spleens infected with bacteria at 6 h, 24 h, and 72 h were obtained using the Illumina sequencing platform. After de novo assembly, a total of 158,124 unigenes were detected. To further investigate the immune-related DEGs, gene ontology (GO) enrichment and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis were performed. Immune pathways about antigen processing and presentation pathway, complement and coagulation cascades pathway, and apoptosis pathway were combined to discussed in this study. Additionally, 10 immune-related DEGs in these three immune pathways were randomly selected for expression verification by quantitative Real-time PCR (qRT-PCR). The data generated in this study provides a valuable resource for further immune response research and offers efficient strategies against E. tarda infection in yellow catfish.