• Journal of fish pathology
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• v.5 no.1
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• pp.9-18
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• 1992

In order to know the defense mechanism of fish, bactericidal activity was examined into the sera of carp Cyprinus carpio, tilapia Oreochromis niloticus and flounder Paralichthys olivaseus. Each examined normal serum of fishes showed the bactericidal activity against avirulent Escherichia coli but it wasn't appeared against virulent Edwardsiella tarda. When the normal serum of each fish was treated with zymosan, it lost the bactericidal activity completely. After addition of EGTA into the normal serum of each fish, the sera of tilapia and flounder still exhibited the bactericidal activity but the serum of carp lost it. In the presence of specific antibody and complement, bactericidal activity of each antiserum was exhibited high level with in one hour incubation. On the other hand, heat inactivated antiserum showed bacteriostatic reaction. From the above results, although the activity of alternative or classical pathway of each fish complement is different, it is an important function in fish defense mechanism.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.1
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• pp.90-96
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• 2013

Effects of dietary Scutellaria baicalensis extract (SBE) on growth, feed utilization and challenge test of olive flounder (Paralichthys olivaceus) were determined. Six hundred thirty fish averaging 5.0 g were distributed into 18, 180-L tanks. Six experimental diets were prepared in triplicate: SBE-0, SBE-0.5, SBE-1, SBE-2, SBE-3 and SBE-5 diets containing SBE at the concentrations of 0, 0.5, 1, 2, 3 and 5%, respectively. Fish were hand-fed to apparent satiation twice a day for 8 wks. At the end of 8-wk feeding trial, ten fish from each tank were infected by Edwardsiella tarda for challenge test. Survival and weight gain of fish were not affected by dietary concentrations of SBE. However, specific growth rate of fish fed the SBE-2 diet was higher than that of fish fed the SBE-0, SBE-1, SBE-3 and SBE-5 diets. Neither feed efficiency nor serum chemical composition of fish was affected by dietary concentrations of SBE. The cumulative mortality of fish fed the SBE-0 diet was 100% at 96 h after E. tarda infection, but 77 to 87% for fish fed the other diets. Dietary inclusion of 2% SBE appears to be recommendable to improve specific growth rate of fish and SBE had the potential to mitigate mortality of fish at E. tarda infection.

• Korean Journal of Microbiology
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• v.22 no.1
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• pp.41-48
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• 1984

Twenty two cultures of pathogenic bacteria were isolated from cultured eels(Anguilla japonica) from Asan Hatchery. The bateria were characterized by their biochemical properties, serological relationships, infectivity to gold fish and susceptibility to various antimicrobial compounds. Fourteen of 22(64%) cultures were identified as Edwardsiella tarda, five (23%) as Aeromonas hydrophila and three (14%) as Vibro anguillarum. Edwardisiella tardo isolates proved to be the main cause of the disease in cultured eels. They were serologically homogeneous and their virulency to gold fish was higher than any of the other groups of bacteria tested. The virulence of 3 isolates were low in gold fish exposed to the bacteria by the waterborn route. Ten strains were tested for their susceptibility to 12 antimicrobial compounds and were resistant to from one to six drugs: in particular, tetracycline derivatives and sulfisoxazole.

• Journal of fish pathology
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• v.16 no.3
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• pp.183-191
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• 2003

The effect of each dietary supplements (Undaria 5%, Undaria 10%, Obosan 0.5%, Wasabi leaf 2%, Wasabi stem 2%) on the water temperature fluctuation in juvenile olive flounder (Paralichthys olivaceus) was investigated. The response to stress was assessed in terms of effects on haematological and immunological, and resistance against Edwardsiella tarda infection. Plasma glucose and cortisol levels were significantly lower in 5% undaria and 2% wasabi leaf supplement groups than the controls after the first change of water temperature (P<0.05). The plasma lysozyme activities and the survival rates from E. tarda infection were significantly higher in the 5% undaria supplement groups than the control (P<0.05). These results suggest that the 5% undaria supplement seems to be contributable to the increased disease resistance on olive flounder.

• Journal of fish pathology
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• v.13 no.1
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• pp.45-51
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• 2000

Bacterial diseases with mixed infection have recently occurred at land-based flounder farms in Korea. Thus, single antibacterial is not effective for therapy of mixed bacterial diseases of fish because of their different causative bacteria. The purpose of the present study was to obtain basic data for positive usefulness of a combination of antibacterials used for synergism to mixed bacterial diseases of fish. Snergistic interaction in combination of antibacterials was determined by in vitro antimicrobial activity against selected fish-pathogenic bacteria, Vibrio anguillarum, Edwardsiella tarda, Streptococcus sp., Staphylococcus epidermidis, on the basis of Checkerboard assay using fractional inhibitory concentration (FIC) indices. Synergistic interactions were observed in combinations of (oxytetracycline HCL+lincomycin), (tetracycline HCL+florfenicol), (oxytetracycline HCL+florfenicol) against V. anguillarum, (sodium nifurstyrenate+florfenicol), (tetracycline HCL+florfenicol), (sodium nifurstyrenate+oxolinic acid), (oxytetracycline HCL+florfenicol) against E. tarda, (ciprofloxacine+oleandomycin), (oxytetracycline HCL+oleandomycin), (tetracycline HCL+oleandomycin), (oxytetracycline HCL+lincomycin), (oxytetracycline HCL+spiramycin), (oxytetracycline HCL+erythromycin), (doxycycline HCL+oleandomycin), (tetracycline HCL+spiramycin) against Streptococcus sp., and (ciprofloxacine+erythromycin), (florfenicol+erythromycin), (doxycycline HCL+oleandomycin), (ciprofloxacine+oleandomycin) against S. epidermidis.

• Journal of fish pathology
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• v.9 no.2
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• pp.195-201
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• 1996

Ninety-six isolates of Edwardsiella tarda recovered from outbreaks of Edwardsiellosis in cultured eels(Anguilla japonica) in Kunsan, were examined for drug susceptibility, distribution and transferabilities of R plasmid. All of the E. tarda isolates examined were sensitive to gentamicin(GM), streptomycin(SM), norfloxacin(NF), and amikacin(AK). But most isolates were resistant to sulfadimethoxine(SD, 86 strains), ampicillin(AM, 84 strains), penicillin G(PM, 80 strains), nalidixic acid (NA, 67 strains), oxytetracycline(OT, 44 strains), and oxolinic acid(OA, 37 strains). Twenty different combinations of drug resistance patterns were observed : the frequently encountered pattern was SD-AM-PM-NA-OA(16 strains), SD-AM-PM-NA(14 strains), SD-AM-PM-NA-OT-OA(12 strains), SD-AM-PM-OT(10 strains), and SD-AM-PM-NA-OT(8 strains). Transferable R plasmids were found out to be carried in 78 out of 94 resistant strains, indicating that these isolates carry conjugally transferable R plasmids associated with single or multiple drugs. The frequently observed transferarble R plasmids were AM(8 strains), AM-PM-NA(8 strains), Am-SD(6 strains), PM(6 strains), and SD(6 strains) These results suggest that high dose of various antibacterials might have already been introduced to eel culture system leading to the acquirement of multi-drug resistance to wide range of antibacterials.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.3
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• pp.672-681
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• 2015

Edwardsiellosis has become a serious diseases problem in cultured eels for many years. This study was performed to investigate possibility of vaccination against edwardsiellosis caused by Edwardsiella tarda. We conducted a immersion and/or oral vaccination using formalin-killed E. tarda in eel Anguilla japonica. Three groups of fish ($26.8{\pm}1.2g$, $7.1{\pm}0.7g$ and $2.2{\pm}0.4g$) were used in this study. The protection (relative percentage survival, RPS) and serum antibody response (agglutination titer) were evaluated in the vaccinated fish. No correlation between agglutination titer and survival rate was observed in vaccinated fish. However, there was a satisfactory protective (RPS>50%) in vaccinated fish. Immersion (10 mg/mL, 1 hr) and immersion (10 mg/mL, 1 hr) plus oral (10 mg/g, 10 days) of $26.8{\pm}1.2g$, immersion (10 mg/mL, 1 hr) plus oral (10 mg/g, 10 days) of $7.1{\pm}0.7g$ showed RPS of 62.6%, 52.2% and 56.8%, respectively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.2
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• pp.236-243
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• 2004

Antimicrobial effect of chitosan and its oligosaccharides was examined on Vibrios sp., Edwardsiella tarda and Streptococcus sp., which are major pathogenic bacteria inducing bacterial diseases of acquacultured flounder. Chitosan oligosaccharides (COS ) were produced by enzymatic hydrolysis of chitosan in an ultrafiltration mombrane bioreactor system which was established with three membranes with different molecular weight cut-off (MWCO) 1,000, 5,000 and 10,000, and fractionated into three kinds of COS, based on their molecular weight sizes. The three kinds of COS were as follows : relatively high molecular weight COS [HMW-COS, molecular weight distribution of 7,000 to 24,000 Da〕, medium molecular weight COS 〔MMW-COS, 1,500 to 6,000 Da〕, and low molecular weight COS 〔LMW-COS, 1,000 to 1,500 Da). Chitosan and HMW-COS effectively inhibited the growths of Vibrio sp. and Streptococcus sp. and their antimicrobial activities were superior to the others with smaller molecular weights. This result suggested that antimicrobial effect of chitosan preparations extremely depend on their molecular weight sizes. Antimicrobial effect of chitosan and HMW-COS on E. tarda was improved by longer inoculation times. Scanning electron microscopy in morphological change of E. tarda treated with chitosan preparations showed that chitosan and HMW-COS bound to the cells and suppressed the growth of the cells. This observation appears to prove the fact that positive charged amines of chitosan electrostatically bind to negative charged compounds of cell walls.

• Journal of Aquaculture
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• v.14 no.4
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• pp.221-226
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• 2001

The ethanol extract of root bark of Morus alba strongly inhibited the Gram positive bacteria like Streptococcus sp., Lactococcus garvieae and Staphylococcus sp., but weakly the Gram negative bacteria like Listonella anguillarm and Edwardsiella tarda. It was more effective in liquid medium than in solid medium. The minimum inhibition concentration (MIC) of the extract in liquid medium was 19.8 and 790~1185 $\mu\textrm{g}$/$m\ell$ for the Gram positive and Gram negative bacteria, respectively. The extract concentration, at which the growth was totally inhibited, was 67.2~403.0 $\mu\textrm{g}$/$m\ell$ for the Gram positive bacteria but it was as high as 1185 $\mu\textrm{g}$/$m\ell$ for L. anguillarum and almost ineffective against E. tarda. For diet supplementation of the extract, effective soaking duration was 3 minutes. The fish diet soaked in the extract inhibited the growth of all the tested Gram positive strains, but not the Gram negative strains. The relationship between the weight of fish diet and absorption of the extract by the fish diet was Y=7.5757X + 4.6962($R^2$ = 0.9998).

• Food Science and Preservation
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• v.22 no.6
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• pp.886-892
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• 2015

The antimicrobial effects of ten isothiocyanates (ITCs) present in cruciferous vegetables and radish root hydrolysate were investigated against pathogenic bacteria from olive flounder. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were measured against two gram-positive bacterial strains (Streptococcus parauberis, S. iniae) and four gram-negative bacterial strains (Edwardsiella tarda, Vibrio ichthyoenteri, V. harveyi, Photobacterium damselae) by using a broth microdilution technique. The antibacterial activity of ITCs was in the order sulforaphane > sulforaphene > phenylethyl ITC > erucin > benzyl ITC > iberin > I3C > allyl ITC > phenyl ITC > hexyl ITC. The susceptibility of fish pathogens to ITCs was in the order of V. harveyi > E. tarda > P. damselae > S. parauberis > S. iniae > V. ichthyoenteri. Antimicrobial activity (MIC) of radish root hydrolysate was 0.250 mg/mL against S. iniae, 0.438 mg/mL against S. parauberis, and 0.500 mg/mL against both E. tarda and V. harveyi. The aliphatic ITCs were potent inhibitors of the growth of fish pathogens, followed by aromatic ITCs and indolyl ITC. The presence of a double bond in the chemical structure of ITCs decreased antibacterial activity, while ITCs with a thiol (-S-) group and a longer carbon chain increased antibacterial activity. These results suggest that ITCs have strong antibacterial activities and may be useful in the prevention of fish pathogens.