• Korean Journal of Microbiology
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• v.30 no.6
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• pp.501-506
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• 1992

An alkalophilic Vibrio sp. RH530 showing high proteolytic activity was isolated form soil samples by enrichment culture. The activity staining using gelatin SDS- polyacrylamide gel electrophoresis (PAGE ) revealed that the strain produced an alkaline major protease (Apr B) with a size of 27 kDa, and at least six minor proteases. The apparent sizes of four of the minor proteases were approximately 45, 28, 22 and 19 kDa. Apr B and five of the minor proteases were inhibited by serine protease inhibitors including PMSF and DFP, suggesting that they are serine proteases. One of the minor proteases was inhibited by metalloprotease inhibitors, not by serine protease inhibitors, indicating it to be a metalloprotease. Furthermore, the activities of Apr B and Prt 3 were not inhibited by SDS in the reaction mixture. The production of Apr B and some of the minor proteases was specifically affected by culture temperature (30 to 37.deg.C) and pH (7 to 10). The production of Apr B. Prt 2, Prt 5 and Prt 6 was mainly affected by culture temperature, while Prt 4 by culture pH. Prt 1 and Prt 3 were not affected by neither of these factors.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.4
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• pp.397-403
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• 2018

We determined the resistance rates of pathogenic bacteria isolated from cultured olive flounder Paralichthys olivaceus to erythromycin (Em), antibiotic typically used in aquaculture and analyzed the genotypes of resistant bacteria using polymerase chain reaction (PCR). We isolated and utilized 160 isolates of Streptococcus parauberis, 1 of S. iniae, 66 of Edwardsiella tarda, 56 of Vibrio sp. and 23 of unidentified bacteria from presumed infected olive flounder from Jeju Island from March 2016 to October 2017. Of the 306 isolated strains, Em-resistant strains included 33 of S. parauberis, 39 of E. tarda and 2 of Vibrio sp. We conducted PCR to assess the resistance determination of Em-resistant strains. Five different types of Em-resistance genes were detected in the 74 Em-resistant strains: erm (A), erm (B), erm (C), mef (A) and mef (E); erm (A) and erm (B) were detected in 1 (3%) and 24 (72.7%) S. parauberis isolates, respectively. In E. tarda, erm (B) was detected in five isolates (12.8 %) and no Em-resistance genes were detected in the two Vibrio sp. isolates.

• Journal of fish pathology
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• v.36 no.2
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• pp.239-250
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• 2023

Disease monitoring was conducted to investigate the recent disease occurrence in Japanese eels (Anguilla japonica). Between May 2021 and March 2022, an investigation was conducted on eels from seven farms experiencing mortality. JEECV (Japanese eel endothelial cells-infecting virus) was detected in all examined farms, each exhibiting co-infections with 1 or 2 bacteria, including Edwardsiella anguillarum, E. piscisida, Aeromonas sp., Citrobacter freundii, Lactococcus garviae, or Vibrio sp. From March 2022 to October 2023, monthly periodic inspections were carried out at a farm in Yeonggwang, Jeollanam-do, for a total of 22 times. JEECV was detected in 10 out of 22 times, even when mortality was not recorded. Bacteria such as E. anguillarum, C. freundii, Aeromonas sp., and Vibrio sp. were isolated, but consistent clinical signs of liver abscess and hemorrhagic lesions were only recognized in fish infected with E. anguillarum. Other bacteria were often isolated from apparently healthy fish. In conclusion, mortality in eel farms frequently occurs due to co-infections of JEECV with bacteria rather than JEECV alone. Therefore, to reduce eel mortality, it is crucial to decrease co-infections, with a particular emphasis of JEECV and E. anguillarum.

• Journal of Food Hygiene and Safety
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• v.15 no.2
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• pp.173-175
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• 2000

Nine strains of pathogenic Vibrio sp. of clinical and environmental origin were examined for the degradation of gelatin, casein and hemolysin which is important to the virulence of this bacterium. Culture filtrates of all nine strains of Vibrio exhibited proteolytic activities. Especially, four strains of V. parahaemolyticus and one V. alginolyticus showed strong gelatin-degrading activity. In terms of hemolytic activity, three V. parahaemolyticus and V. mimicus showed strong $\beta$-hemolysis whereas those of strains of V. alginolyticus, V. fluvialis, V. vulnificus examined lacked this activity.

• Journal of fish pathology
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• v.13 no.1
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• pp.1-6
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• 2000

The antibacterial activity of marine bacterium(Pseudomonas aeruginosa JYMB1-3) was assayed against Vibrio anguillarum with the aim of evaluating the possible use for biocontrolling fish disease as probiotic strain. Inhibition test on the solid medium showed that vibrios were especially sensitive to the JYMB1-3. Edwardsiella tarda, Streptococcus sp. and Staphylococcus epidermidis were also sensitive to that strain, however the antibacterial abilities were varied to the pathogens. The vibriostatic activity of antibacterial substance produced from $10^7$ cells of the strain for 24 hours was equivalent to $2.5{\mu}g$ of chloramphenicol.

• Journal of Life Science
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• v.27 no.10
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• pp.1161-1167
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• 2017

In order to find a new antimicrobial bacterium, we performed screening for antimicrobial activity of bacteria isolated from the eggs of a sea hare. The newly identified strain was designated as Phaeobacter inhibens KJ-2, based on the biochemical characterization and 16S rRNA gene sequence analysis. A colony of P. inhibens KJ-2 showed a circular and ruler-like smooth form at the edge, and a brown color. However, when maintained with a longer incubation time, its coloring was transformed into dark brown. From the result of SEM, P. inhibens KJ-2 is a bacillus which has a length of $0.8{\sim}1.0{\mu}m$ and a width of $0.4{\sim}0.6{\mu}m$. The optimal growth and antimicrobial activity were observed by shaking the culture for 24 hr at $20^{\circ}C$, which showed potent activity against pathogenic bacteria including Vibrio logei, Vibrio campbellii, Vibrio mimicus, Vibrio vulnificus, and Vibrio salmonicida. The antimicrobial activity was proportional to the amount of produced acylated homoserine lactones (AHLs). Therefore, we suggest that production of antimicrobial materials from P. inhibens KJ-2 is regulated by Quorum sensing (QS).

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.2
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• pp.222-227
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• 2001

The members of the genus Vibrio include harmless aquatic strain as well as strains capable of causing infections in human and fish. Pathogenic mechanisms are only understood for Vibrio cholerae O1 and O139 and not for the majority of Vibrio species. Twelve clinical and nonclinical strains were examined by in vitro and in vivo experiments for the importance of extracellular enzymes as a virulence determinant of Vibrio species. In vivo cytotoxicity assay was performed by injecting approximately $10^{8}$ cells/mL into mice (BALB/c). V. harvyi and V. vulnificus showed 100% lethality within 3hr after bacterial injection. V. fluvialis and four strains of V. parahaemolyticus showed 50% lethality within 4hr. V. mimicus, V. alginolyticus and V. furnissii revealed 30% lethality within 9hr. Nonclinical strains, V. campbellii and V. ordalii, did not show any lethality. In vitro protease and hemolytic activities were also good indicators for clinical and nonclinical strains of Vibrio species. The clinical strains showed much higher activities than nonclinical strains. The activity of some clinical strains of re-isolates was evidently increased. Most clinical strains had $\beta$ hemolytic activity. The results demonstrate that the prevalent distribution of extracellular proteases in pathogenic Vibrio sp. implies their importance as a virulence determinant.

• Journal of fish pathology
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• v.16 no.2
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• pp.135-138
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• 2003

The research was carried out to know the occurrence trend of scuticociliatosis and mortality of fingerlings in flounder. The diseased fish were collected from on-land rearing farms lind hatcheries of flounder in Jeju Island from January 1991 to December 2001. Occurrence of scuticociliatosis was about 10% of total occurred diseases from 1991 to 1996, but increased to 34.5% in 2001. Although monthly occurrence of scuticociliatosis was not related to season from 1999 to 2001, the highest occurrence was revealed in July and August. Mixed infections of bacteria including Vibrio sp. Edwardsiella tarda, Streptococcus sp., and Flexibacter sp. with scuticociliates were observed. Among the bacteria, Vibrio sp. was the highest frequency(40.1%), and the lowest one(10.1%) was Streptococcus sp., Mortality of fingerlings by scuticociliates was different sharply according to size of fish. Mortality of infected fingerlings below 7 cm of total length was 53.8%, while that of normal fingerling above 7 cm of total length was 13.2%. When fish were grown above 25 cm, mass mortality by scuticociliates infection was decreased markedly.

• Journal of Aquaculture
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• v.16 no.2
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• pp.118-123
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• 2003

This study was conducted to investigate the disinfection effects of chlorine dioxide ($ClO_2$) on 4 fish pathogenic bacteria (Vibrio anguillarum, Edwardsiella tarda, Streptococcus sp. and Staphylococcus sp.) isolated from infected olive flounders. The bacteria were exposed to different concentrations of ClO$_2$ (0.129, 0.246 and 0.455 ppm) and response times (0.5, 1, 3, 5 and 10 min), and then were incubated for 12 hr. The effective disinfection concentrations of $ClO_2$ against experimental bacteria by $ClO_2$ for 0.5 min were observed with 0.455 ppm for Staphylococcus sp., 0.246 ppm for V. anguillarum and E. tarda, and 0.129 ppm for Streptococcus sp., respectively. The duration of exposure at low concentration of $ClO_2$ increased for the disinfectant ability to experimental bacteria.

• 한국수산학회:학술대회논문집
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• 2005.05a
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• pp.223-224
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• 2005