• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.5
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• pp.620-628
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• 1996

To avoid the self-agglutination of Staphylococcus aureus sensitized with rabbit antibody in the absence of antigen, we determined the optimum concentration of rabbit antibody for sensitization. It was analyzed by using three different kinds of S. aureus strains at various concentraions of antibody. The optimized coagglutination test using the S. aureus sensitized with rabbit antibody was applied to the diagnosis of edwardsiellosis in field and in laboratory. The presence of E. tarda as low as $10\;{\mu}g/ml$ was detected by this method. Moreover, it showed good coagglutination results against several different forms of antigens such as FKC, EDTA or heat extracted antigen of E. tarda. E. tarda strains, isolated from the flounders suffering from edwardsiellosis in fields, showed some cross-reactions to the E. tarda 219 analyzed by both agglutination and coagglutination test with rabbit anti-E, tarda 219 antibody. The degree of cross-reactions analyzed was enough to apply the coagglutination test for the diagnosis of edwardsiellosis in field. Thus, even 1,000 fold diluted tissue homogenate of infected flounder naturally contained enough E. tarda as an antigen to show good coagglutination with S. aueus sensitized with rabbit anti-E, tarda 219 antibody. The successful application of this method to the homogenate and heat extract of tissues from naturally or artificially infected flounder or tilapia preyed that coagglutination test was a simple and rapid reliable dignostic technique suitable for using in laboratory and field without any special equipments.

• Journal of fish pathology
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• v.19 no.3
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• pp.285-288
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• 2006

The respiratory burst activity of tilapia (Oreochromis mosambicus) phagocytes agaisnt Edwardsiella tarda ghosts produced by gene E mediated lysis was investigated. Stimulation with E. tarda ghosts (ETG) showed markedly higher respiratory burst activity than that with formalin killed E. tarda (FKC) in phagocytes. This result may suggest that ETG can induce effective cellular immune responses in fish.

• Journal of Life Science
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• v.21 no.10
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• pp.1487-1493
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• 2011

E. tarda, a fish pathogen, can survive in seawater under relatively high salt conditions as well as in fish under physiological salt conditions. Bacterial growth under different salt concentrations may influence the expression of genes involved in bacterial structure and physiology. The growth rate of E. tarda culture in high salt (3.5% NaCl) was similar to that in low salt (1.0% NaCl, physiological salt concentration). Interestingly, the strain moved much faster in low salt conditions than in high salt conditions. Electron microscopic observation demonstrated that the bacterial cells grown in high salt had less or no flagellation. Obvious flagellation was observed in the parental strain E. tarda CK41 grown in low-salt condition. Two putative genes coding flagellin were identified in the E. tarda genome sequences. The amino acid sequence comparison of each gene revealed 93% identities. A flagellin gene was PCR amplified and cloned into a cloning vector. Using an E. coli protein expression system, a part of flagellin protein was overexpressed. Using the purified protein, an anti-flagellin antibody was raised in the rabbit. Immunoblot analyses with flagellin specific antibody demonstrated that E. tarda CK41 expressed falgellin in low salt conditions, which is consistent with the results seen in motility assay and microscopic observation. This is the first report of salt regulated flagella expression in E. tarda.

• Journal of fish pathology
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• v.31 no.2
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• pp.93-99
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• 2018

Edwardsiella tarda predominantly causes edwardsiellosis in fish at high temperature, but is rarely isolated from water when water temperature is low. However, E. tarda is viable but nonculturable (VBNC) in low water temperature, but it can be revived when water temperature rises and cause disease to fish. Therefore, in order to prevent disease, it is very important to identify pathogens that are in the VBNC state in environmental water. In this study, E. tarda cells in the VBNC state were detected by the ethidium monoazide (EMA)-PCR method using the low-temperature oligotrophic sea water microcosm obtained by inoculation of E. tarda at a concentration of $10^8CFU/ml$. In order to distinguish between live and dead bacteria in E. tarda, each sample was treated with EMA at different concentrations, photoactivated with a 500 W halogen lamp, and PCR was performed with E. tarda specific primer. At the concentration of $10^7CFU/ml$ bacterium, DNA amplification was observed only in the live cells when treated with $60{\mu}g/ml$ of EMA, and smaller amounts of live cells could be distinguished from dead cells by adjusting the EMA concentration. In addition, the VBNC cells of E. tarda in the oligotrophic low temperature seawater microcosm were estimated to be in the range of $10^4{\sim}10^5CFU/ml$ by EMA-PCR. Therefore, it is possible to detect VBNC cells that will act as potential pathogens in environmental water using EMA-PCR method, and quantitative confirmation using concentration change is also possible.

• Journal of fish pathology
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• v.12 no.2
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• pp.115-121
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• 1999

MIC test of 16 chemotherapeutic agents was performed on 24 isolates of Edwardsiella tarda collected from flounders. They revealed resistance against combinations of ampicillin, amoxicillin, erythromycin, flumequine, doxycycline(DOXY), nalidixic acid, novobiocin, oxolinic acid, oxytetracycline(OTC), thiamphenicol(TP) and sulfonamide. Two strains carried transferable R plasmid encoding Otc Kanamycin Tp and Otc chloramphenicol Doxy Tetracycline Tp, respectively. The R plasmids were not similar each other on the basis of their digestion pattern of restriction endonuclease, suggesting distribution of different transferable R plasmid among E. tarda from flounders.

• Korean Journal of Environmental Biology
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• v.19 no.2
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• pp.173-181
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• 2001

To find the appearance period and distribution of Edwardsiella tarda which causes severe damage to flounder (Paralichthys olivaceus) farms in Jeju-do, the rearing seawater (inflow, rearing water, outflow) and internal organs of flounders from 5 flounder farms were examined from June, 1997 to May, 1998. The number of bacteria in seawater was counted by plating the seawater on DSSS (Double Strength Salmonella-Shigella) agar plates or by plating after cultivation of bacteria. Bacteria in internal organs were counted by plating series of dilution of homogenized organ. The results are summarized as follows. E. tarda was detected in inflow seawater of five flounder farms in July, September and November, 1997 and February, March, April of 1998. In the rearing water and outflow water, the bacterium was detected throughout the year and the number of bacteria was much higher in summer than any other seasons. A large number of E. tarda in the internal organs were detected at farm B where a track-shaped tank was used, which has the characteristics of low circulation rate and bad discharge of excrement and residuals. In contast, none of E. tarda was detected at farm A where high circulation rate and good discharge of organic materials were applied. A few number of E. tarda at farm E were detected at the same condition as the farm A. A large number of E. tarda was observed in liver and intestines among the internal organs, and the number was higher from June to September in summer.

• Journal of fish pathology
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• v.19 no.1
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• pp.45-54
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• 2006

The immunogenicity of Edwardsiella tarda was surveyed under two different culture conditions. In SDS-PAGE patterns of the outer membrane proteins (OMPs) extracts of E. tarda, grown under Trypic soy broth (TSB) and TSB supplemented iron chelate 2,2‘-dipyridyl iron-restricted condition, were examined. The results showed that the iron-regulated outer membrane protein (IROMPs) with molecular masses of 68 and 73 kDa were expressed by bacteria grown in iron-chelate TSB.The pathogenicity was examined by intraperitoneal injection with live E. tarda grown under TSB, iron-chelate TSB and iron-supplemented TSB. The result of pathogenicity test showed significantly high mortality in the group of live E. tarda grown under iron-chelate TSB.The effect of formalin killed cell (FKC) of TSB cultured bacteria and 2,2'-dipyridyl FKC (DP-FKC) of cultured bacteria on the iron-chelate TSB on the development of protective immunity in olive flounder was studied. The level of immune response was evaluated with immunized fish at 1, 2, 3 and 4 weeks after immunization. The numbers of specific antibody secreting cells (SASCs) showed significantly increased level at 2 week after immunization in each group. The agglutination titre of immunized fish was significantly high level at 3 weeks after immunization.The level of protection in olive flounder at 1, 2, 3 and 4 weeks after vaccination was examined by intraperitoneal challenge test with live E. tarda.

• Journal of Veterinary Clinics
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• v.31 no.6
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• pp.502-506
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• 2014

Recently nano particles have proven for wide array of bioactive properties. In the present study, antibacterial properties of chitosan silver nano composites (CAgNCs) were investigated against fish pathogenic Edwardsiella tarda. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of CAgNCs against E. tarda were $25{\mu}g/mL$ and $125{\mu}g/mL$, respectively. The field emission scanning electron microscope (FE-SEM) image of CAgNCs treated E. tarda showed the strongly damaged bacteria cells than non-treated bacteria. Furthermore, treatment of CAgNCs induced the level of intracellular reactive oxygen species (ROS) in E. tarda cells in concentration and time dependent manner suggesting that it may generate oxidative stress leading to bacterial cell death. In addition, MTT assay results showed that the lowest cell viability at $100{\mu}g/mL$ of CAgNCs treated E. tarda. Overall results of this study suggest that CAgNCs is a potential antibacterial agent to control pathogenic bacteria.

• Food Science and Preservation
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• v.18 no.1
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• pp.87-90
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• 2011

The methanol extracts of 19 commercial herb medicines was analyzed to antibacterial activities against Edwardsiella tarda, causing several fish diseases. Rhus javanica showed most strong antibacterial activity against E. tarda and Escherichia coli. Methanol extract of R. javanica was further extracted using several organic solvents having different polarity. Extract from ethyl acetate fraction showed strong activity against E. tarda as well as E. coli. Minimal inhibitory concentration, MIC of R. javanica extract was measured and resulted showing $64\;{\mu}g/m{\ell}$ for E. tarda and $256\;{\mu}g/m{\ell}$ for E. coli. It is needed that, from these results, further purification and isolation of reposible compound of these activities and further study on the synergy effect using combination with antibiotics against pathogenic bacteria.

• Journal of fish pathology
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• v.18 no.3
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• pp.227-237
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• 2005

To obtain antimicrobial compounds against fish pathogenic bacteria from natural products, 80% methanolic extracts from 14 species of medicinal plant were screened for antimicrobial activity against fish pathogenic bacteria, Edwardsiella tarda and Vibrio anguillarum. Among them, Glycyrrhiza glabra, Rhus vemiciflua and Sanguisorba officinalis were effective for growth inhibition of Gram-negative bacteria, both E. tarda YSF and V. anguillarum YSR. Through the activity-guided isolation for R. verniciflua extract that exhibited the highest antimicrobial activity among three extracts, one antimicrobial compound (1) was isolated and identified as methyl-3,4,5-trihydroxybenzoate, or methyl gallate. This compound significantly inhibited the growth of tested strains of both E. tarda and V. anguillarum exhibiting MIC of 1 mg/ml for each strain.