• Journal of fish pathology
• /
• v.35 no.1
• /
• pp.121-128
• /
• 2022

Recent studies revealed that histone proteins are involved in innate immune responses during pathogen invasion as well as DNA packing. This study characterized the histone genes (H2A.V) of sevenband groupers and analyzed gene expression in NNV-infected sevenband groupers. The open reading frame (ORF) of H2A.V is 387 bp which encoded 128 amino acid residues. The deduced amino acid sequence of H2A.V harbor a highly conserved domain for H2A/H2B/H3 and H2A_C binding domain. Quantitative real-time PCR analysis showed that H2A.V had a high gene expression level in the brain and blood after being NNV-infected. An increase in extracellular histone protein in the blood has been identified as a biomarker for vascular function in humans. More research is required to understand histone's immune response at the protein level or in aquatic animals.

• Fisheries and Aquatic Sciences
• /
• v.26 no.10
• /
• pp.605-616
• /
• 2023

Scuticociliatosis, caused by the parasitic pathogen Miamiensis avidus, poses a significant threat to olive flounder farms in South Korea. Infected fish suffer from severe systemic infections affecting various organs, with potential secondary bacterial diseases. This study investigated the emergence of different M. avidus serotypes in 20 olive flounder farms on Jeju island, South Korea, from 2015 to 2020. Additionally, we identified Tenacibaculum maritimum as a co-infecting bacteria. Based on serotyping and monitoring data, we developed a trivalent vaccine targeting two serotypes of M. avidus and one strain of T. maritimum. The efficacy of the vaccine was evaluated under laboratory conditions and demonstrated a relative percentage of survival (RPS) of 75%, 80%, and 93% for M. avidus serotype I, M. avidus serotype II and T. maritimum, respectively. Furthermore, successful field trials conducted on four different olive flounder farms resulted in significantly higher survival rates (52%-76% RPS) and weight gains in vaccinated fish. Overall, this study presents an effective vaccine against M. avidus and T. maritimum infections in farmed olive flounder, making a valuable contribution to sustainable aquaculture in South Korea.

• Journal of fish pathology
• /
• v.34 no.1
• /
• pp.105-110
• /
• 2021

We experienced mortality of dark-banded rockfish (Sebastes inermis) maintained in the rearing facility located in Gangneung, after transportation. Moribund fish showed various symptoms such as exophthalmia, skin ulcers, tail rots, gill rots, discoloration of liver with petechiae, yellowish fluid in intestines and ascites. Two different colonies were dominantly appeared after spreading the lesions on the agar plates and incubation. One isolate (SI_1) showed swarming movement on TSA, and formed yellow colonies on TCBS agar. The other (SI_2) showed no swarming motility and green colonies on TCBS agar. Both of them were Gram-negative. All of these results are similar with those of Genus Vibrio. They were identified as V. harveyi and V. gigantis by PCR with subsequent sequencing of 3 different genes (16 rDNA, recA, rpoA). V. harveyi is well-known as a serious pathogen of marine fish and invertebrates, while V. gigantis is known to be often isolated from marine invertebrates, but the pathogenicity is still unknown. We suspect V. harveyi as the cause of the mortality of dark-banded rockfish, but challenge experiments with these 2 Vibrio species are thought to be necessary to make a clear conclusion.

• 한국생물공학회:학술대회논문집
• /
• 2005.10a
• /
• pp.899-903
• /
• 2005

Two infectious species of Streptococcosis pathogens were detected by multiplex PCR assay. Detection rates of Streptococcus iniae and S. parauberis could reach 44.9% and 55.1% respectively for one year during 2004 to 2005 in Jeju island. These findings showed that S. parauberis strains were important pathogen with streptococcosis of olive flounder in Jeju island. These findings showed that S. parauberis strains were important pathogen with streptococcosis of olive flounder in Jeiu island. In the present study we have investigated the interspecific relationship of all Jeju area of S. parauberis by RAPD analysis. Represent strains divided to four groups by RAPD fingerprints. The important differences observed between the olive flounder isolates suggest that they could constitute a well-differentiated group or a separate clonal line within this bacterial species. Though, serological research of S. parauberis strains in Jeju island not exist yet. These strains doing the serological evolution.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.53 no.3
• /
• pp.443-450
• /
• 2020

No established method can be used to select effective antibiotics in antibiotic susceptibility tests for fish bacterial pathogens quickly and accurately. Here, we established the optimal conditions for determining the minimal inhibitory concentration (MIC) of major fish bacterial pathogens (Streptococcus spp., Edwardsiella tarda, Vibrio spp., Aeromonas spp., and Pseudomonas spp.) using the KRAQ1 and CAMPY2 panels. The MIC panel used 18 antibiotics of two types and we conducted experiments to establish the optimal culture medium and temperature for each species. The optimal conditions for incubating Streptococcus spp. were in cation-adjusted Mueller-Hinton broth with TES buffer (CAMHBT) at 28℃, using 5% lysed horse blood (LHB) as recommended by the Clinical Laboratory Standards Institute. For Vibrio spp., the optimal culture conditions were 28℃ in CAMHBT supplemented with 1% NaCl. The optimal conditions for culturing E. tarda, Aeromonas spp., and Pseudomonas spp. were in CAMHBT at 28℃.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.48 no.3
• /
• pp.346-353
• /
• 2015

Glucocorticoids (GCs) are steroid hormones regulated through responses to stress to maintain diverse metabolic and homeostatic functions. GCs act on the glucocorticoid receptor (GR), a member of the nuclear receptor family. This study identified and characterized the GR gene from the big-belly seahorse Hippocampus abdominalis designating it HaGR. The open reading frame of the HaGR cDNA was 2,346 bp in length, encoding a 782-amino-acid polypeptide with a theoretical isoelectric point of 6.26 and predicted molecular mass of 86.8 kDa. Nuclear receptors share a common structural organization, comprising an N-terminal transactivation domain, DNA-binding domain, and C-terminal ligand-binding domain. The tissue-specific mRNA expression profile of HaGR was analyzed in healthy seahorses using a qPCR technique. HaGR mRNA was expressed ubiquitously in all of the tissues examined, with the highest expression levels in kidney, intestine, stomach, and gill tissues. The mRNA expression in response to immune challenge with lipopolysaccharide (LPS), polyinosinic:polycytidylic acid (poly I:C), Edwardsiella tarda, and Streptococcus iniae revealed that it is inducible in response to pathogen infection. These results suggest that HaGR is involved in the immune response of the big-belly seahorse.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.34 no.4
• /
• pp.365-369
• /
• 2001

Streptococcus spp. of bacterial pathogen of fish were isolated from the cultured flounder (Paralichthys olivaceus) in fish farm of Jeju Island. Clinical signs of the infected flounder which are the most commons symptoms are as follows: erratic swimming, darkening of the body colour, unilateral or bilateral exophthalmia, corneal opacity, hemorrhages in the opercular and the bases of the fins, and the ulceration of the body surface. Biochemical characteristics of pathogenic fish Streptococcus spp, were gram positive, spherical form, catalase negative, oxidase negative and $\beta$-haemolytic, respectively, The viable cells counted from the tissue of the diseased flounder were the largest in the order of the ulcer, the kidney, the blood and the brain, The drugs used were ampicillin, ciprofloxacin, doxycycline, gentamycin, tetracycline, erythromycin, streptomycin and oxytetracycline, Streptococcus spp. were found to be sensitive to ampicillin, ciprofloxacin, doxycycline and gentamycin, but were resistant to tetracycline, erythromycin, streptomycin and oxytetracycline. The pathogenicity of Streptococcus spp. on the cultured flounder with an abdominal cavity injection was high. The haemolytic activity of the toxin against the sheep red blood cells reached the maximum after 30 min incubation at $37^{\circ}C$ or $50^{\circ}C$. The toxin showed highest activity at pH $5.5\sim6.5$.

• Journal of fish pathology
• /
• v.22 no.3
• /
• pp.317-326
• /
• 2009

This study has shown the screening of anti-bacterial activity of three Indian medicinal plant choloroform : methanol (50:50) solvent leaf extracts (i.e. Azadirachta indica, Ocimum sanctum, and Curcuma longa) with different concentrations (10, 5, 2.5, 1.25, 0.625, 0.312, and 0.156 mg/ml) under in vitro conditions against fish pathogenic bacteria, Aeromonas hydrophila, Streptococcus iniae, Vibrio harveyi, V. anguillarum, and Edwardsiella tarda isolated from olive flounder farms, Jeju Island, South Korea. The anti-microbial activity of the A. indica and O. sanctum extracts yielded the zones of growth inhibition (ZI) was 3 and 1mm against A. hydrophila at concentration of 0.156 mg/ml when compared to that of tetracycline standard (3 mm). At highest concentration (10 mg/ml) of A. indica, O. sanctum, and C. longa, high inhibition was 9, 7, and 6 mm when compared to that of tetracycline (11 mm) against A. hydrophila. The minimum inhibitory concentration (MIC) of A. indica, O. sanctum, and C. longa at 0.156 mg/ml that yield 9, 10, and 13 CFU/ml for A. hydrophila, 16, 22, and 25 CFU/ml for S. iniae and 18, 22, and 23 CFU/ml for E. tarda compared to the tetracycline. At highest concentration (10 mg/ml) of the three extracts was better inhibiting the growth of A. hydrophila, S. iniae and E. tarda. A. indica, O. sanctum, and C. longa were determined to the potential antioxidant activityon the basis of their scavenging activity of the stable 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical. A. indica extract was 0.625 mg/ml which indicated that the strong anti-oxidant activity. However, O. sanctum and C. longa extracts showed weak anti-oxidant activity at this concentration. Hence, in vitro assay among the pathogens, A. hydropila is better inhibitory activity of the extracts. It is evident that the Indian medicinal plants extracts were subjected to its effectiveness against A. hydrophila, S. iniae, and E.tarda at low concentrations. The obtained results in the present study suggested that the Indian plant extracts is a prevention tools for Korean olive flounder aquaculture pathogens and its need further advance investigation.

• Fisheries and Aquatic Sciences
• /
• v.14 no.4
• /
• pp.347-354
• /
• 2011

Aeromonas salmonicida is an important fish pathogen commonly associated with furunculosis in salmonids. Typical A. salmonicida strains have the surface virulence A-layer protein, a major virulence determinant encoded by the vapA gene. In this study, 880 chum salmon Oncorhynchus keta were collected from the east coast of Korea during 2006-2011, including 560 wild adults and 320 artificially hatched fry pools, and the presence of typical A. salmonicida was examined by PCR using the typical A. salmonicida-specific vapA gene primers. The results demonstrated that 34.5% of the samples (304/880 samples) were PCR positive, implying that a typical A. salmonicida infection is highly prevalent among chum salmon in Korea. Twenty typical A. salmonicida isolates were recovered based on their brown pigmentation on Trypticase Soy Agar (TSA) plates, which indicates the existence of the A-layer protein. Further biochemical analyses with the four randomly selected typical A. salmonicida isolates revealed some variations in their amino acid decarboxylation and carbohydrate fermentation activity. A phylogenetic analysis based on the entire vapA gene sequence suggested that the A. salmonicida isolates from chum salmon were clustered with those isolated from Atlantic salmon in Europe. Further study is needed to resolve such an interesting relationship in detail.

• Korean Journal of Organic Agriculture
• /
• v.19 no.spc
• /
• pp.39-42
• /
• 2011

This experiment was conducted to evaluate the effect of two different organic acid products as antibiotic replacement in olive flounder paralichthys olivaceus. Fish averaging $3.5{\pm}0.05$ g($mean{\pm}SD$) were fed one of the ten semi-purified diets : Diet 1 ; Control, Diet 2 ; add antibiotics - 50mg OTC/kg body weight/day(OTC), Diet 3 ; Add organic acid bland A(OABA) - 4g/kg diet, Diet 4 ; add organic acid bland B(OABB) - 4g/kg diet for 10 weeks. Total gut microflora counts were significantly higher in the control group compared to the OTC and organic acid groups(P<0.05). Fish fed OABA, OABB and OTC had lower gut Vibrio counts compared to the control, but were not significantly different. Results from the challenge study indicate that mortality in the different treatment groups (50%) was significantly lower than those observed for the control group (100%). There were no differences in mortality between the OTC and organic acid groups. Overall findings from this study indicate that the organic acid blends A and B were as effective as oxytetracycline, an antibiotic, in regulating total gut bacterial numbers, Vibrio counts and providing protection against a pathogen such as Edwardsiella tarda.