• Journal of fish pathology
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• v.5 no.1
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• pp.37-48
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• 1992

Antibiotics are chemical substances produced by various species of microorganisms that suppress the growth of other microorganisms or may destroy them. Among the more than 4000 antibiotics that has been identified, about 20s are using as the therapy of infectious fish diseases. There are several methods used to classify and group antibiotics, and the most common classification has been based on chemical structure and proposed mechanism of action. The effect of antibiotics may be determined by the kind of fish pathogens and by the external environment surrounded the infected fish. It implies that the kind of antibiotics and its application method should be decided after the determination of the reasons of fish disease. The uncontrolled usages of antibiotics may induce the selection of resistant mutants appeared spontaneously and present in any group of bacteria. The epidemic spread of such antibiotic resistant strains of fish pathogenic bacteria already has been reported in various districts of japan. Importantly, transferable drug resistant(R) plasmids were detected in strains of most of fish pathogens. Based on those reports, the antimicrobial resistance appears to be a rapidly emerging problem in the fish industry on the country. The expanding literatures on the pharmacokinetics, clinical trials, withdrawal periods and efficacy of environmental effect for the commonly using antibiotics have met the needs of data for the practical application of antibiotics. However, the most important thing for the treatment of fish diseases would be the communication and exchanging of information between the site of aquaculture and the diagnostic laboratory.

• Journal of Life Science
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• v.24 no.8
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• pp.880-886
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• 2014

In this study, we isolate and identify bacteria from seawater collected from Jeju coast, to evaluate the antimicrobial activity against the fish pathogenic bacteria. 14 bacterial strains were isolated and identified using physiological, biochemical and molecular tools. Antibacterial activity of all the 14 isolates were screened against four major fish pathogens namely, two Gram-positive: Streptococcus iniae, Streptococcus parauberis and two Gram-negative: Vibrio anguillarum, Edwardsiella tarda. Results revealed that among the 14 isolates, MK-11 was found to have antibacterial activity against S. iniae, S. parauberis, V. anguillarum Particularly, S. iniae was susceptibility with the MIC value of $250{\mu}g/ml$. The biochemical and physio-chemical results reveal that MK-11 had the sugar-alcohol disassemble ability of the D-sorbitol and D-mannitol. Also the utilization of the yeast extract, sorbitol and di-potassium phosphate were noted to be high. The optimum culture condition such as pH and temperature was recorded as pH 6.0, $25^{\circ}C$ and along with 1% NaCl which differs from the previous reports particularly in nutrient resolutions. As results of the analysis of 16S rDNA sequences, MK-11 show the high similarity with Paenibacillus polymyxa, P. jamilae, P. brasilensis 99.78%, 99.43%, 99.39%, repectively. Hence, in the present study, the isolated Paemibacillus sp. MK-11 from Jeju seawater possesses the antibacterial activity against fish pathogens and it could be used as a new antibiotic agents against the gram positive fish pathogens.

• Fisheries and Aquatic Sciences
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• v.22 no.12
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• pp.30.1-30.11
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• 2019

Marine natural products isolated from the sponge Fascaplysinopsis cf reticulata, in French Polynesia, were investigated as an alternative to antibiotics to control pathogens in aquaculture. The overuse of antibiotics in aquaculture is largely considered to be an environmental pollution, because it supports the transfer of antibiotic resistance genes within the aquatic environment. One environmentally friendly alternative to antibiotics is the use of quorum sensing inhibitors (QSIs). Quorum sensing (QS) is a regulatory mechanism in bacteria which control virulence factors through the secretion of autoinducers (AIs), such as acyl-homoserine lactone (AHL) in gram-negative bacteria. Vibrio harveyi QS is controlled through three parallel pathways: HAI-1, AI-2, and CAI-1. Bioassay-guided purification of F. cf reticulata extract was conducted on two bacterial species, i.e., Tenacibaculum maritimum and V. harveyi for antibiotic and QS inhibition bioactivities. Toxicity bioassay of fractions was also evaluated on the freshwater fish Poecilia reticulata and the marine fish Acanthurus triostegus. Cyclohexanic and dichloromethane fractions of F. cf reticulata exhibited QS inhibition on V. harveyi and antibiotic bioactivities on V. harveyi and T. maritimum, respectively. Palauolide (1) and fascaplysin (2) were purified as major molecules from the cyclohexanic and dichloromethane fractions, respectively. Palauolide inhibited QS of V. harveyi through HAI-1 QS pathway at 50 ㎍ ml^-1 (26 μM), while fascaplysin affected the bacterial growth of V. harveyi (50 ㎍ ml^-1) and T. maritimum (0.25 ㎍). The toxicity of fascaplysin-enriched fraction (FEF) was evaluated and exhibited a toxic effect against fish at 50 ㎍ ml^-1. This study demonstrated for the first time the QSI potential of palauolide (1). Future research may assess the toxicity of both the cyclohexanic fraction of the sponge and palauolide (1) on fish, to confirm their potential as alternative to antibiotics in fish farming.

• Journal of fish pathology
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• v.21 no.3
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• pp.271-278
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• 2008

The epidemiological study was performed to survey the prevalence of 5 bacterial, 6 viral and 5 parasitic disease of cultured olive flounder, Paralichthys olivaceus in Pohang, Ulsan∙Gijang, Keoje and Wando area of Korea from February to December, 2007. The disease frequency of size groups were as follows; Among the 1,218 fish samples, less than 10 cm (67.6%), 11~20 cm (70.2%), 21~30 cm (73.4%), 31~40 cm (77.6%), above 41 cm (88.2%). The highest detection rates of pathogens were recorded in samples from August and Ulsan. The detection rates of parasites, bacteria or viruses were 43.2%, 38.8% and 24.4%, respectively. The distribution of specific diseases showed that detection rates of diseases occurring the most frequently during the study period were Trichodina (33.1%), viral nervous necrosis virus (16.0%), Vibrio (9.7%), Scutica (10.1%), Ichthyobodo (5.7%).

• Journal of fish pathology
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• v.1 no.2
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• pp.103-110
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• 1988

For the rapid diagnosis of bacterial diseases of cultured fishes, the immunoperoxidase method was applied to the detection of $\beta$-haemolitic Streptococcus sp. strain KST-2 isolated from tilapia(Oreochromis niloticus). The suitability of field analysis and the sensitivity of the immunoperoxidase method was compared with those of the counterimmunoelectrophoresis(CIE) and the immunodiffusion(ID). Results of testing cross-reactivity which did not indicate any cross reactivity with other fish pathogens, this method was specific to Streptococcus sp. The sensitivity of this method was $1{\times}10^3CFU/ml$ which was at least $10^2$times greater than the CIE and $10^4$times greater than the ID. The immunoperoxidase method was more suitable for field application and more sensitive than other diagnostic techniques tested on this study.

• Microbiology and Biotechnology Letters
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• v.44 no.4
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• pp.535-539
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• 2016

The prevalence of pathogenic bacteria such as Streptococcus parauberis (Sp), Streptococcus iniae (Si), and Edwardsiella tarda (Et) in flounder fish farms in Jeju Island and their management by gallium treatment was studied. Sp, Si, and Et were found to exhibit a low rate of cell growth and high biofilm formation. Hence, in the present study, cell growth and biofilm formation were measured spectrophotometrically 72 h after the addition of different concentrations of gallium (2, 4, or 8 mg/ml). In addition, cell death was measured by resazurin and propidium iodide staining assays. The results showed that bacterial cell death increased and biofilm formation decreased with an increasing concentration of gallium. Hence, the present study signifies that the use of gallium against bacterial pathogens could be useful for disease management in flounder farms.

• Journal of fish pathology
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• v.25 no.3
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• pp.165-172
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• 2012

Vibrio alginolyticus (V. alginolyticus), which is one of bacterial pathogens evoking severe infection in fish and shellfish as well as in human has been found at high frequency around all coast areas in Korea. Both V. alginolyticus and V. alginolyticus specific bacteriophage were isolated from sea water and various fishes from fish farms on west coast in Korea. In a morphological study based on electron microscope, the purified phage appeared to be composed of hexagon head of 60 nm and short tail of 20 nm. In the denatured SDS-PAGE analysis, the structural proteins of the phage were found to be 7 different protein fractions ranging from 37.8 to 198 kda. The kind of nucleic acid of the phage was ascertained to a double stranded DNA.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.634-643
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• 2021

Han In-jin (Artemisia iwayomogi Kitamura) and Cham Dang-gwi (Angelica gigas Nakai) exhibit antibacterial, antiparasitic, antifungal, and antiviral properties in vitro. In this study, mixture of the extracts of these two medicinal plants was absorbed on pellets. Thereafter, these pellets were fed to olive flounder Paralichthys olivaceus for 12 weeks at laboratory (1^st experiment) and 24 weeks at field test (2^nd experiment), and the immune activity and disease resistance properties of the extracts were examined. It was observed that lysozyme activities of plasma, spleen, and kidney improved after 12 weeks. Furthermore, when the olive flounders were artificially infected with bacterial pathogens, their cumulative mortality decreased in the group that was fed the extracts for 12 weeks compared to that in control group, and the relative percent survival also improved. This study concluded that mixture of Han In-jin and Cham Dang-gwi extracts provides disease resistance in vivo.

• Journal of Microbiology and Biotechnology
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• v.30 no.10
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• pp.1443-1457
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• 2020

The emergence and spread of antimicrobial resistance in pathogenic bacteria of fish and shellfish have caused serious concerns in the aquaculture industry, owing to the potential health risks to humans and animals. Among these bacteria, Aeromonas salmonicida, which is one of the most important primary pathogens in salmonids, is responsible for significant economic losses in the global aquaculture industry, especially in salmonid farming because of its severe infectivity and acquisition of antimicrobial resistance. Therefore, interest in the use of alternative approaches to prevent and control A. salmonicida infections has increased in recent years, and several applications of bacteriophages (phages) have provided promising results. For several decades, A. salmonicida and phages infecting this fish pathogen have been thoroughly investigated in various research areas including aquaculture. The general overview of phage usage to control bacterial diseases in aquaculture, including the general advantages of this strategy, has been clearly described in previous reviews. Therefore, this review specifically focuses on providing insights into the phages infecting A. salmonicida, from basic research to biotechnological application in aquaculture, as well as recent advances in the study of A. salmonicida.

• Journal of Microbiology and Biotechnology
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• v.10 no.5
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• pp.595-598
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• 2000

Aeromonas hydrophila is a pathogen to fish as well as human. It is a food-borne disease, and causes severe mortality in fish, and sometimes severe septicemia in human. In this study, a rapid detection method using latex agglutination has been developed for A. hydrophila. Polyclonal antibodies were raised against membrane and whole cells of three isolates from rainbow trout. Among these, latex particles coated with antibodies raised against whole cells of isolate No. 2 showed the best sensitivity. With latex particles coated with this antibody, we could detect $5{\times}10^4$ CFU of A. hydrophila in 5 min. The cross-reactivity with bacteria constituting the normal intestinal microflora and other pathogens for rainbow trout was insignificant. This latex agglutination assay method produced positive reaction with all clinical isolates of A. hydrophila which were identified by species-specific PCR for 16S rRNA in A. hydrophila.