• Journal of Aquaculture
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• v.21 no.4
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• pp.325-330
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• 2008

Two different Eelwardsiella tarda isolates, KFE and Edk-2, were obtained from Korea and Japan respectively. On the base of the previous results showing higher pathogenicity of E. tarda KFE compared to that of E. tarda Edk-2 isolate, we tried to determine the differences of antigenicities of these two isolates in loach which is one of the important species in freshwater aquaculture in Korea. Concentration of specific antibody in the serum appeared to be much higher in loach immunized with FKC of E. tarda Edk-2 than those found in loach immunized with FKC of E. tarda KFE. Cross-reaction analysis using agglutination test with normal and antigen-absorbed antisera implied the differences epitopes in the antigens of these E. tarda isolates. For the comparison of bactericidal activity of the produced antibody with different antigens, absorption analysis was performed and confirmed the presence of critical epitopes in the FKC of E. tarda KFE strain. The prophylactic agent, polysaccharide-bound protein (PS-K) injected 1 week before the artificial infection with E. tarda KFE isolates decreased the cumulative mortality in loach and would be on effective method to prevent the occurrence of bacterial infection including E. tarda.

• Journal of Marine Bioscience and Biotechnology
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• v.1 no.3
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• pp.218-223
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• 2006

The present study evaluated effect of egg yolk immunoglobulin (IgY) from the hen immunized with Edwardsiella tarda. The purification of anti-E. tarda IgY was performed by polyethylene glycol (PEG). Purified IgY had heavy chain of 64 kDa and light chain of 27 kDa size. The IgY was instable against olive flounders digestive factors and artificially modulated pH 2 and 3. Nevertheless, some activity of IgY appeared in intestine. IgY was orally administered with viable E. tarda to the olive flounders and the efficacy of protection against E. tarda infection was evaluated. Orally administered IgY at a dose of 20 mg/fish delayed infection period of E. tarda cannulated at $10^{6{\sim}8}CFU/fish$ to small size (30~40 g) and middle size (110~120 g) flounder. Moreover, orally administered IgY at dose of 20 mg/fish inhibited the penetration of E. tarda cannulated at $10^8CFU/fish$ into the liver, kidney, spleen and gill via intestine. The fish orally administered with IgY showed increased survival rate. These results suggest that egg yolk containing anti-E. tarda IgY is effective in preventing edwardsiellosis.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.6
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• pp.1193-1200
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• 2014

Edwardsiella tarda, Streptococcus iniae and S. parauberis are main bacterial pathogens in aquaculture farms of olive flounder, Paralichthys olivaceus. We have discussed the efficacy and safety of 3 type-combined vaccines (A: S. iniae 1mg + S. parauberis 1mg + E. tarda 1mg, B: S. iniae 1mg + S. parauberis 1mg + E. tarda 0.5mg, C: S. iniae 1.5mg + S. parauberis 1.5mg + E. tarda 1mg) through intraperitoneal injections in olive flounder. None of the vaccines gave rise to any signigicant side effects on histopathology and blood chemistry. The antibody titers and lysozyme activities of A type were higher than those of B, C and control. Four weeks after vaccination, RPS (relative percent survival rates) was 62.5~75% (A type), 50~66.7% (B type) and 55.6~62.5% (C type) respectively. As the results, the combined vaccines are possible to prevent edwardsiellosis and streptococcosis, and A type : S. iniae 1mg + S. parauberis 1mg + E. tarda 1mg, is the most effective out of them.

• Fisheries and Aquatic Sciences
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• v.25 no.4
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• pp.243-249
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• 2022

Bacillus SW1-1 is a probiotic isolated from shrimp intestines. We investigated the effects of Bacillus SW1-1 coated diets on the growth, feed utilization, innate immunity, hematological parameters and resistance to Edwardsiella tarda in olive flounder (Paralichthys olivaceus). A commercial diet was used as the control (AP0) and two other diets were prepared by coating 0.25% (AP25) or 0.50% (AP50) probiotic powder which contains 1.0 × 10⁷ CFU/g Bacillus SW1-1. Four replicate groups of olive flounder (153 ± 2 g) were fed one of the diets for 12 weeks. Growth performance and feed utilization of the fish were not significantly affected by the dietary Bacillus SW1-1. After the challenge with E. tarda, AP50 group showed significantly higher survival than AP0 and AP25 groups. Innate immunity and anti-oxidant capacity of the fish were not significantly affected after the feeding trial. However, after the E. tarda challenge, the innate immune parameters (immunoglobulin, lysozyme and anti-protease) were significantly improved in fish fed AP25 and AP50 diets compared to those in fish fed AP0 diet. After the challenge test, significantly lower glucose level was observed in AP50 group compared to AP0 group. These results indicate that dietary supplementation of Bacillus SW1-1 could increase the disease resistance of olive flounder against E. tarda infection. The optimum coating levels of Bacillus SW1-1 needs to be further elucidated.

• Journal of Aquaculture
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• v.5 no.2
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• pp.143-155
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• 1992

Effects of vitamin E, C and/or glycyrrhizin in the artificially oxidized feed on the growth and on the resistance aganist Edwardsiella tarda infection to Nile tilapia, Oreochromis niloticus, were examined. The thiobarbitric acid (TBA) values of the oxidized feed were $80\~88$ mg/kg. The fingerling fish were fed the oxidized feed with or without the mixture of vitamin E (50 mg), C (60 mg) and/or glycyrrhizin ($25\~200$ mg) per 100 g of the feed for 7 weeks. The fish fed the oxidized feed with vitamin E, C and/or glycyrrhizin showed better growth than the fish fed the oxidized feed only. But growth rates among the fish fed different amount of vitamins or glycyrrhizin mixed feed were not different. Glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) levels in the serum increased only in the fish which were fed oxidized feed without vitamin E, C and/or glycyrrhizin. With the fish artificially infected with E. tarda: they showed low survival rate when fed oxidized feed and oxidized feed plus 25 mg glycyrrhizin per 100 g feed. The fish fed oxidized feed plus vitiamin E, C and/or glycyrrhizin ($50\~200$ mg/100 g), showed higher survival. These results show that the supplementation of oxidized lipids depress the growth and liver activity, while the addition of vitamin E, C and/or glycyrrhizin in the diet accelerated the growth, liver activity, and the resistance to E. tarda infection.

• Journal of fish pathology
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• v.27 no.1
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• pp.35-45
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• 2014

In this study, we investigated the effects of dietary 1% garlic extract on nonspecific immune responses and fish diseases (Viral Hemorrhagic Septicemia Virus, Vibrio anguillarum, Streptococcus iniae and Edwardsiella tarda) resistance in olive flounder Paralichthys olivaceus. Fish were fed a commercial diets supplemented with 1% garlic extract for 4 weeks. After the 4 weeks feeding experiment, the artificial infection was made by V. anguillarum, S. iniae, E. tarda and VHSV. And the cumulative mortality was monitored for 2 weeks after artificial infection. The cumulative mortalities decreased in all experiments except for group of E. tarda compared to control group. We observed significantly higher levels of the hematocrit, glucose, total protein, lysozyme activity and the macrophage activity in the experimental group compared to the control group. In the experiments of drug sensitivity and MIC using the three bacteria (V. anguillarum, S. iniae and E. tarda), 1% garlic extract was more effective than the previously reported fermented garlic powder. These results suggested that garlic extract can increase the disease resistance of olive flounder against V. anguillarum, S. iniae and VHSV and the ability of nonspecific immune responses.

• Journal of fish pathology
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• v.5 no.2
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• pp.61-75
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• 1992

Experimental infection method for Edwardsiellosis was studied to imitate histopathologically natural infections in the Tilapia Oreochrimis niloticus. Prior to the bacterial challenge, the intestine of tilapia was damaged by 0.2ml of 30% hydrogen peroxide introduced through a silicon tube which was inserted 4 to 5cm into the intestine from anus. E. tarda was mixed a 10% Gum arabia and administered into the stomach by a cannula 20 hours after the hydrogen peroxide treatment. Bacterial doses used were from $4.2{\times}10^6$ to $6.4{\times}10^\;CFU$/fish. Fish 72 hours after the challenged showed swollen and erosious lesion and focal necrosis with bacterial-eaden inflammatory cell in the Liver, Spleen, Kidney. Fish 96 and 120 hours after bacterial challenge were moribund showing swollen Liver, Spleen, Kidney and focal accumulation of macrophages and production of granulomas in the infected lesions.

• Journal of fish pathology
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• v.10 no.1
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• pp.45-52
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• 1997

A protein-bound polysaccharide preparation, PS-K, isolated from Coriolus versicolor was evaluated for its ability to enhance resistance against Edwardsiella tarda, causal agent of classical edwardsiellosis in tilapia, Oreochromis niloticus. Fish treated with a dose rate of 0.1 mg PS-K $g^{-1}$ body weight were challenged by intraperitoneal injection of E. tarda with different concentrations. Against low burdens of injections($1.2{\times}10^7$ and $1.2{\times}10^8$ cfu/fish), PS-K treated fish did not show any mortality compared to 50% and 100% mortality of control groups, respectively. However there was no increase of resistance against challenge with high concentrations of E. tarda ($1.2{\times}10^9$ and $1.2{\times}10^{10}$cfu /fish) except few days delaying of death. Tilapia injected with PS-K one day after intraperitoneal inoculation of E tarda($1.2{\times}10^7$ cfu/fish) showed 100% survival rate compared to control group of 50% survival rate. The result indicates the potential of PS-K as a prophylactic agent in aquaculture. The increased antibody response in fish received PS-K one week prior to FKC administration suggested the influence of PS-K on the specific humoral immunity and increased resistance against bacterial infection.

• Journal of Fisheries and Marine Sciences Education
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• v.24 no.4
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• pp.591-601
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• 2012

Olive flounders, Paralichthys olivaceus, were intraperitoneally challenged with Edwardsiella tarda or Streptococcus iniae or both bacteria simultaneously. The pathogenicity was respectively compared with blood chemical using alanine aminotransferase (ALT), aspatate aminotransferase (AST), glucose and total protein, lysozyme activity, bacterial number of kidney and spleen, histopathological change, and cumulative mortality. The tested group of coinfection showed increased cumulative mortality, bacterial number of kidney and spleen, AST and histopathological change, but not in lysozyme activity compared with others. This study provides support for the conclusion that simultaneous infection with Edwardsiella tarda and Streptococcus iniae in a susceptible host results in higher pathogenicity, leading to the increment of bacterial number and the destruction of the internal organs.

• Journal of Microbiology and Biotechnology
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• v.19 no.8
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• pp.765-773
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• 2009

Edwardsiella tarda is a pathogen with a broad host range that includes human and animals. The E. tarda hemolysin (Eth) system, which comprises EthA and EthB, is a noted virulence element that is widely distributed in pathogenic isolates of E. tarda. Previous study has shown that the expression of ethB is regulated by iron, which suggests the possibility that the ferric uptake regulator (Fur) is involved in the regulation of ethB. The work presented in this report supports the previous findings and demonstrates that ethB expression was decreased under conditions when the E. tarda Fur ($Fur_{Et}$) was overproduced, and enhanced when $Fur_{Et}$ was inactivated. We also identified a second ethB regulator, EthR, which is a transcription regulator of the GntR family. EthR represses ethB expression by direct interaction with the ethB promoter region. In addition to ethB, EthR also modulates, but positively, luxS expression and AI-2 production by binding to the luxS promoter region. The expression of ethR itself is subject to negative autoregulation; interference with this regulation by overexpressing ethR during the process of infection caused (i) drastic changes in ethB and luxS expressions, (ii) vitiation in the tissue dissemination and survival ability of the bacterium, and (iii) significant attenuation of the overall bacterial virulence. These results not only provide new insights into the regulation mechanisms of the Eth hemolysin and LuxS/AI-2 quorum sensing systems but also highlight the importance of these systems in bacterial virulence.