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

• Journal of fish pathology
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• v.33 no.1
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• pp.63-69
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• 2020

Fish culture is constantly threatened by various infectious diseases which are largely transmitted by water. Plasma technology is being used to sterilize polluted water in many industries. In this study, two bacterial pathogens Aeromonas salmonicida and Streptococcus iniae, and a virus (viral hemorrhagic septicemia virus, VHSV) were subjected to plasma water that was produced by a corona discharge system. Growth of A. salmonicida was greatly inhibited from 10^5.61 CFU/ml in positive control to 10^3.51 CFU/ml in treated group by only 60 sec contact with plasma water. Similarly, S. iniae was inhibited from 10^5.85 CFU/ml to 10^3.40 CFU/ml. VHSV titer also decreased from 10^4.1 TCID₅₀/ml to 10^1.45 TCID₅₀/ml by the same treatment. Activation of water by the plasma was confirmed by the existence of ozone in the plasma water. These results suggest that plasma water could efficiently disinfect fish pathogens, possibly by the action of reactive oxygen species contained in the plasma water.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.3
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• pp.323-329
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• 2016

The effects of dietary antioxidant [saltwort (SW), leek (LK), and dandelion (DD)] supplementation on the growth, body composition, serum chemistry, and challenge test results of juvenile rockfish, Sebastes schlegelii, were determined. In an experiment, 320 fish were randomly distributed into eight, 50-L flow-through tanks (40 fish per tank). Four experimental diets were prepared: the control diet (Con) with synthetic antioxidant: and diets with SW, LK, or DD from natural sources. Each diet was randomly assigned to duplicate tanks of fish, which were hand-fed to satiation twice daily for 8 weeks. After the 8-week feeding trial, 20 fish from each tank were artificially infected with Streptococcus iniae and monitored for 6 days. The dietary additives did not affect survival, weight gain, specific growth rate, feed efficiency (FE), protein efficiency ratio (PER), or plasma chemistry. However, the cumulative mortality of fish fed the SW, LK and DD diets was lower than that of fish fed the control diet beginning 4 days after infection. In conclusion, dietary supplementation with SW, LK, and DD did not affect the growth, FE, PER, or plasma chemistry of rockfish. However, dietary inclusion of SW, LK, and DD lowered the mortality of rockfish following infection with S. iniae.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.6
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• pp.578-582
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• 2002

Ethanol extract obtained from bark, roots, stem, leaves and seeds of 30 species of plants and mushroom, Dicyophora indusiata were examined antimicrobial effect on fish pathogenic bacteria, Listoneria anguillamm, Lactococcus garvieae, Streptococcus iniae by disk method. Ethanol extract of D. indusiata was found to be the most active against all fish pathogenic bacteria in test system. Ethyl acetate fraction from ethanol extract of D. indusiata showed the strongest compared with those from other solvent fractions such as dichloromethane, n-buthanol and water. The antimicrobial effect of ethyl acetate fraction was particularly evident against S. iniae.

• Journal of fish pathology
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• v.21 no.1
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• pp.29-34
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• 2008

In this study, we examined in vitro antimicrobial activity of the hydrolysis compound (MBT-01108) of cactus stem (Opuntia ficus-indica var. saboten Makino) against 18 strains of fish pathogenic bacteria, Edwardsiella tarda, Listonella anguillarum, Vibrio sp., Lactococcus garvieae, L. raffinose, Streptococcus parauberis and S. iniae. Antibiotic susceptibility of the same bacteria was also assayed to commercial discs containing various antibacterials. According to these results, MBT-01108 showed the excellent antimicrobial activity against the tested pathogenic bacteria.

• Journal of Marine Bioscience and Biotechnology
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• v.14 no.2
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• pp.86-92
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• 2022

In this study, the antibacterial activity of major compounds obtained from domestic plant essential oils was investigated against four species of fish pathogenic bacteria, namely, Edwardsiella tarda, Vibrio harveyi, Streptococcus iniae, and Streptococcus parauberis. We observed that α-terpineol and eucalyptol showed high antibacterial activity against S. iniae, whereas α-terpineol and β-linalool showed high antibacterial activity against S. parauberis. The antibacterial activity of eucalyptol and β-linalool was significantly high against E. tarda, and α-terpineol and β-linalool exerted antibacterial activity against V. harveyi. All compounds showing significant antibacterial activity also exhibited high solubility in water (≥1,000 mg/L). In contrast, compounds such as α-limonene and α-pinene with low water solubility showed significantly low antibacterial activity against all bacteria. These findings can be utilized further to estimate the antibacterial activity of compounds isolated from plant essential oils for the prevention of fish disease.

• Journal of fish pathology
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• v.27 no.1
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• pp.47-56
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• 2014

Propolis is a beehive product with a very complex chemical composition, widely used in folk medicine because of its several therapeutic activities. This study was conducted to measure the efficacy of propolis on non-specific defense reactions, specific immune response, and protection levels against pathogen challenge with Streptococcus iniae. in vitro and in vivo. In vitro, the phagocytic activity and NBT assay of peripheral blood leukocytes (PBL) were evaluated in a various propolis extractsconcentrations (0, 10, 50, 100, 150, 250 and $500{\mu}g/ml$). The optimal concentration showing activation of propolis extracts was determined to $100{\mu}g/ml$. In vivo, they were divided into four groups (PBS, propoli extractss, vaccine, propolis extracts + vaccine) in vivo. Fish were received i.p. injection of either PBS or propolis extracts, and in the presence or absence of formalin inactivated S. iniae ($1{\times}10^8$ CFU/fish), respectively. The level of haematocrit is not affected among experimental groups. The phagocytic activity and the NBT reduction activities of head kidney phagocyte were markedly (p<0.05)augmented in the propolis extracts groups than in the PBS-control group, respectively. The level of serum lysozyme activity was significantly (p<0.05) increased in the propolis extracts treated groups than in the PBS-control group. The agglutinin titer was significantly (p<0.05) enhanced in the vaccine+propolis extracts group than in the vaccine group, but there was no difference between PBS-control and propolis treated group. The results of the present study suggest that propolis extracts seems to be a promising compounds of non-specific immune stimulator, also being able to use a good adjuvant.

• Journal of fish pathology
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• v.19 no.1
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• pp.73-82
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• 2006

Streptococcal infections were considered as a serious problem because of significant economic losses in fish farm industry. We evaluated the efficacies of Streptococcus iniae vaccines in olive flounder, Paralichthys olivaceus. The vaccines were prepared from 10% neutral buffered formalin to give a final concentration of 0.3% or 3%, respectively. Fish were immunized by intraperitoneal injection of the experimental vaccines once or twice. Neither of the vaccines gave rise to any significant side effects. The antibody titers of booster immunized groups were significantly higher than those of prime immunized groups with both of the vaccines. According to formalin dosage, significantly increased antibody titers were produced by 3% formalin-killed cells (FKC) at 4weeks and 8weeks after prime and booster vaccination, respectively. Although the different levels of antibody production were showed by the vaccinated fish, the good protection obtained in challenge trials of the both vaccines. Fish immunized with 0.3% FKC once or twice had the relative percent survival (RPS) of 66.7% and 87.5%, respectively. Similarly, fish immunized with 3% FKC once or twice had the RPS of 70.0% and 77.0%, respectively. Further experiments are needed to study not only correlation between the antibody titers and RPS against S. iniae but also the side effects of high dose of formalin on antigenicity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.644-652
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• 2011

Two consecutive studies were conducted to evaluate the effects of dietary supplementation with fermented garlic powder (FGP) or fermented garlic fluid (FGF) on growth performance, immune responses, and disease resistance of olive flounder Paralichthys olivaceus. In experiment I, olive flounder (BW: 65 g) were fed four experimental diets formulated to contain 0%, 0.5%, 1%, and 1.5% FGP (designated as FGP-0, FGP-0.5, FGP-1, and FGP-1.5, respectively). After the 10-weeks feeding trial, feed intake was significantly lower in fish fed the FGP-0.5 and FGP-1.0 diets, as compared to those fed the control diet. Fish fed the FGP-0 and FGP-0.5 diets showed significantly lower survival, as compared to the other treatments. Dietary supplementation with FGP resulted in higher non-specific immune responses than the FGP-0 group. Plasma cholesterol and triglyceride levels decreased as dietary FGP level increased. In experiment II, olive flounder (BW: 65 g) were fed four experimental diets for 10 weeks. The diets were prepared with a commercial expanded pellet to have 0%, 0.25%, 0.5%, and 1% FGF (designated as FGF-0, FGF-0.25, FGF-0.5, and FGF-1, respectively) by adsorption. At the end of the second feeding trial, feed intake was significantly lower in fish fed the FGF-0 diet, as compared to other treatments. Fish fed the FGF-0.25 and FGF-0.5 diets exhibited significantly lower cholesterol levels, as compared to other treatments. Lysozyme activity significantly increased with increases in dietary FGF. Cumulative mortality in a challenge test with Streptococcus iniae was significantly lower in the fish groups fed FGF-supplemented diets than in fish fed the control diet. The results of this study indicated that dietary supplementation with FGP or FGF can enhance the non-specific immune responses and disease resistance of olive flounder against S. iniae.

• Journal of Marine Bioscience and Biotechnology
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• v.11 no.2
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• pp.42-51
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• 2019

We compared the antibacterial activities of spermidine and astaxanthin against two gram-positive bacteria such as Streptococcus parauberis and S. iniae to find new antibacterial candidates. We also evaluated the preventive effects of spermidine against oxidative stress-induced cytotoxicity in C2C12 myoblasts. Our results indicated that spermidine has more significant antibacterial activities than astaxanthin against both two fish pathogenic bacteria as well as gram-negative bacteria Escherichia coli used as a control group. Minimum inhibitory concentration and minimum bactericidal concentration of spermidine were 0.25 mM and 1 mM against S. parauberis, 1 mM and 3 mM against S. iniae, and 0.5 mM and 1.5 mM against E. coli, respectively. In addition, the postantibiotic effect lasted from 7 h, 5 h and 6 h for S. parauberis, S. iniae and E. coli, respectively. The results also showed that the decreased C2C12 cell viability by H₂O₂ could be attributed to the induction of DNA damage and apoptosis accompanied by the increased production of reactive oxygen species, which was remarkably protected by spermidine. Additionally, the antioxidant effect of spermidine was associated with the activation of Nrf2 signaling pathway. According to the data, spermidine may be a potential lead compound which can be further optimized to discover novel antibacterial and antioxidant agents.