• Korean Journal of Veterinary Service
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• v.20 no.1
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• pp.11-18
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• 1997

Characteristics, pathogenicity and control of the causative organisms isolated front diseased cultured flounder, Paralichthys olivaceus were studied. The causative organisms were identified as E tarda by biochemical and biophysical characteristics. Also, it strains were named as E tarda KBF-1 and E tarda KMF-1, and optimal pH of E tarda KBF-1 and E tarda KMF-1 were 8.0, and optimal concentration of NaCl. E tarda KBF-1 was 0% and E tarda KMF-1 was 1%. In the pathogenicity test, 0~10 of the flounders of artificially infected group(E tarda KBF-1) with $1.0{\times}10^7$ cfu/fish were died within 60 hrs, but 0~9 flounders infected group with 41.0{\times}10^6$ cfu/fish were died within 60 hrs. Also, 0~10 flounders infected group(E tarda KMF-1) with $1.0{\times}10^7$ cfu/fish were died within 36 hrs, while 0~7 flounders infected with $1.0{\times}10^6$ cfu/fish were died within 60 hrs. Drug sensitivity of E tarda KBF-1 strain was resistant to AM, CF and N, and intermediate to E, K and S, and sensitivity to C, G, SxT and FF. But E tarda KMF-1 strain was resistant to CF, E and V, and intermediate to AM, C, N and SxT, and sensitivity to GM and FF.

• 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 fish pathology
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• v.34 no.1
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• pp.31-38
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• 2021

The objective of this study was to determine comparative biochemical characteristics and RAPD (random amplified polymorphic DNA) profiles of 18 strains of Edwardsiella tarda isolated from cultured olive flounder (Paralichthys olivaceus) and eel (Anguilla spp) that showed diseases between 1996 and 2010 in Korea. In terms of biochemical properties, they showed four patterns with differences in citrate degradation and production of H₂S and indole. All strains were identified as E. tarda. Characteristics of isolates were not classified according to their host. As a result of PCR with E. tarda-specific primer, EDtT, the same band of about 270 bp was detected in all 18 isolates. However, no specific band was detected in type strains of E. tarda or Edwardsiella ictaluri. As a result of RAPD PCR performed with primer No. 5 and No. 6 of a Ready-To-Go-RAPD kit, the band profile showed clear differences among isolates of olive flounder, isolates of eel, and E. tarda and E. ictaluri type strains. It was possible to organize their characteristics according to the origin of host with possibility to develop tools for pathogen monitoring.

• Korean Journal of Ichthyology
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• v.19 no.2
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• pp.83-87
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• 2007

Edwardsiella tarda, a gram (-) pathogen causing edwardsiellosis in farmed fish, was transformed via electroporation with a plasmid expression vector driving the PhiX174 E-lysis gene under the transcriptional control by lambda PR regulatory sequence. The persistent maintenance of the plasmid vector in recombinant E. tarda was found in numerous subculture procedures over up to 6 months without any adverse effect on the original copy number of plasmids. Comparative examination based on semi-quantitative RT-PCR analysis on transcriptional efficiency of E-lysis gene between recombinant E. coli and E. tarda indicated that promoter strength and induction capacity of bacterial ghosts would be retarded in E. tarda as compared to the E. coli. However, the completeness of induction for bacterial ghosts in E. tarda was the same with E. coli, in which at least 99.99% of induction rate was possible and further the viability of recombinant bacteria was completely eliminated by a post-induction procedure including washing and freeze drying lyophilization.

• Journal of fish pathology
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• v.24 no.2
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• pp.85-93
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• 2011

Edwardsiella tarda is a broadly infectious agent against freshwater and seawater fishes. In the present study, E. tarda specific phage was isolated from fish farms on the west coast of Korea, and the effect of environmental factors such as pH and water temperature on the phage activity was investigated. As a fish model, Nile tilapia (Oreochromis niloticus) was used and the interaction between E. tarda and phage was investigated. The phage activity, in pH test, appeared even higher in seawater than freshwater and was evenly constant up to $50^{\circ}C$. The phage and E. tarda were inoculated in tilapia and the phage activity and E. tarda viability were checked on the time intervals. As a result, the number of E. tarda in the group of E. tarda plus phage was constantly reduced to 24 hr post-inoculation compared to the control group without phage, whereas the phage activity was slightly increased in the experiment group. The results suggest that it might be possible to use phage to control the fish disease caused by E. tarda.

• Korean Journal of Microbiology
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• v.52 no.3
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• pp.313-318
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• 2016

Bacteria in the viable but nonculturable (VBNC) state fail to produce colonies on routine bacteriological media, but are still alive in the state of very low metabolic activity. The aim of the present study was to induce the VBNC state of the Edwardsiella tarda using sea water microcosm under starvation conditions at $10^{\circ}C$ and to investigate resuscitation of the VBNC cells in temperatures changed from 10 to $25^{\circ}C$, with and without additives. E. tarda entered into the VBNC state within about 42-84 days of incubation in the microcosm. Throughout this period, the total cell counts as determined using acridine orange direct counting remained near the original inoculum level of ${\sim}10^8cells/ml$. The live cell counts measured with direct viable counting, on the other hands, declined to ${\sim}10^4cells/ml$. When the VBNC cells were incubated with addition of yeast extract, fish muscle extract or serum at $25^{\circ}C$, the ratios of resuscitated samples were 37%, 23%, and 37%, respectively. The characteristics of resuscitated E. tarda were consistent with those of the original E. tarda. When the resuscitated E. tarda were intraperitoneally injected into olive flounders, all fishes died within 5 days, indicating that the VBNC E. tarda might retain its pathogenic potential. Therefore, E. tarda under starvation conditions in the winter enter into the VBNC state and the VBNC E. tarda cells resuscitated at summer and autumn seawater temperature are considered to be pathogen continuously to olive flounder on the southern coast of Korea.

• Journal of fish pathology
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• v.17 no.1
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• pp.11-20
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• 2004

The present study compared purification methods of hen egg yolk immunoglobulin (IgY) from the hen immunized with Edwardsiella tarda. The purification of anti-E. tarda IgY was performed by four different methods, polyethylene glycol (PEG), chloroform polyethylene glycol (Chloroform-PEG), ammonium sulfate and purification kit. Purified IgY had heavy chain of 64 kDa and light chain of 27 kDa size. IgY purified from the hen immunized with E. tarda showed higher ELISA values and agglutination titers than those with IgY purified from the non-immunized hen as a negative control. In addition, purified IgY recognized similar E. tarda proteins to those with anti-E. tarda rabbit serum by western blotting. Purified IgY had an agglutination titer of 1:512 by PEG method and ammonium sulfate method, and 1:128 by chloroform-PEG method and purification kit. Moreover, PEG method was the most rapid method among the four different IgY purification methods. These results indicate that PEG method is effective purification method maintaining biological activity of the IgY.

• Journal of fish pathology
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• v.26 no.3
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• pp.185-191
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• 2013

The present study was performed to investigate an antibacterial activity of specific bacteriophage (phage) and Bacillus subtilis KM-1 (B. subtilis) mixture against Edwardsiella tarda (E. tarda). An appropriate number of phage showing the most effective antibacterial activity was $2{\times}10^5$ PFU/ml with $1{\times}10^7$ CFU/ml of B. subtilis 36 h post incubation. On the other hand, B. subtilis showed a dose dependant manner in inducing antibacterial activity in the presence of phage ($2{\times}10^5$ PFU/ml). The phage and B. subtilis mixture showed higher antibacterial activity against E. tarda than phage or B. subtilis only. These results suggest that the phage and B. subtilis mixture could be utilized as an alternative to antibiotics in the control of fish diseases caused by E. tarda.

• Journal of fish pathology
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• v.21 no.3
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• pp.201-208
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• 2008

We compared the pathogenicity and antigenicity of two different Edwardsiella tarda (E. tarda) strains KFE and Edk-2 isolated in Korea and Japan respectively. In the pathogenicity analysis with challenge test against loach, E. tarda KFE isolate showed stronger pathogenicity compared to that of E. tarda Edk-2 isolate. The differences were also confirmed by the comparison of OMP (outer membrane protein) in SDSPAGE which showed three major bands, 41kDa, 37kDa and 30kDa, for E. tarda KFE isolates and two major bands, 41kDa and 30kDa, for E. tarda Edk-2 isolates. On the base of these results, 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. Numbers of specific antibody secreting cells (SASC), appeared to be higher in loach immunized with FKC of E. tarda Edk-2 than loach immunized with FKC of E. tarda KFE. ELISPOT-assay for the comparison of antigenicity showed relatively high percentage of cross-reaction and implied the presence of some common epitopes in the antigens of these two E. tarda isolates.

• Journal of Life Science
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• v.20 no.12
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• pp.1743-1749
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• 2010

A research group demonstrated that the 37 kDA protein of Edwardsiella tarda, a causing causative agent of edwardsiellosis in fish, exhibited high antigenicity in Japanese flounder. The research group also showed that the N-terminus amino acid sequences of the 37 kDa protein were mapped to the N-terminus of GAPDH (glyceraldehyde-3-phosphate dehydrogenase). Using degenerated primer sets based on the known N-terminus sequence, the corresponding E. tarda DNA was amplified and cloned. The nucleotide sequences of the cloned gene revealed high homology with a bacterial gene for GAPDH, as we was expected. The amino acid sequence of E. tarda GAPDH (etGAPDH) revealed a <70% similarity with GAPDH proteins in other Enterobacteriaceae. With the application of artificial protein overexpression system in Escherichia coli, the recombinant etGAPDH (rGAPDH) was produced and purified. In this study, Using the purified rGAPDH, the etGAPDH specific polyclonal antibody has been was generated using the purified rGAPDHin this study. The immunoblotting analyses demonstrated that the location of the GAPDH protein is located with the association of is associated with the envelops of E. tarda. The rGAPDH was administrated into Japanese flounder via IP route for evaluation of the protective ability. Although the specific antibody titer against etGAPDH was increased about 3-fold after 4 weeks post-vaccination, the survival rates of vaccinated Japanese flounder and the control group with wild type E. tarda was were 12.5% and 0%, respectively. Our results indicated that rGAPDH is immunoreactive antigen but that it will not generate protective immunity in Japanese flounder.