• 한국어병학회지
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• 제33권1호
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• pp.97-101
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• 2020

Although aquaculture production rates grown over the years, aquatic animal diseases occur every year which causes substantial economic losses. When an aquatic animal is infected with an aquatic animal pathogen it is either incinerated or buried according to the aquatic life disease control act. Although these methods prevent the spread of disease, it is not environment friendly. Here, we developed an aquatic animal rendering equipment for disposal of fish waste which is environment-friendly and efficient. Also, fertilizer components of fish waste were evaluated value for recycling. The mobile rendering equipment was designed for field operation and/or high temperature and pressure system, oil and water separator, and shredding drying apparatus. During the experiment (July-2016 to November-2016), a total of 53,824 kg fish waste was collected, and 29,216 kg compost of rendering by-product was made. Also, compost made from viral (Viral hemorrhagic septicemia virus) infected fish did not reflect any detectable pathogen. The concentration of nitrogen, phosphorus, and organic matter in the fish waste compost were 2.17%, 26.98%, and 92.44%, respectively. The results suggest that fish waste used in this study was decomposed efficiently as per the official standard for fertilizer product. This equipment can be useful for efficient inactivation of the aquatic animal pathogenic agents and recycling of the fish waste in an environment-friendly manner.

• 한국어병학회지
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• 제26권3호
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• pp.207-217
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• 2013

최근 울산광역시 소재의 넙치 양식장에서 체색 흑화, 간 위축, 장관 백탁 등의 증상을 보이며 넙치의 대량 폐사가 빈번히 발생하여, 병원체를 분리하고 감염 특성에 관하여 연구하였다. 2012년 5월 병어로부터 분리한 원인균은 생화학 시험과 16S rRNA, dnaJ gene을 이용한 염기서열 분석을 통해 V. scophthalmi로 동정하였다. 병원성 시험 결과, 본 시험 균주가 $10^6$ CFU/fish에서 75%의 누적 폐사율을 보여 강한 병원성이 확인되었다. V. scophthalmi 감염어는 조직병리학적 병변으로서 간 위축, 장 상피 탈락, 장내 세포 물질 유출 및 장관백탁증 등이 확인되었다.

• Journal of Microbiology and Biotechnology
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• 제26권8호
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• pp.1457-1463
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• 2016

Vibrio anguillarum, a devastating pathogen causing vibriosis among marine fish, is prevailing in worldwide fishery industries and accounts for grievous economic losses. Therefore, a rapid on-site detection and diagnostic technique for this pathogen is in urgent need. In this study, two mouse monoclonal antibodies (MAbs) against V. anguillarum, 6B3-C5 and 8G3-B5, were generated by using hybridoma technology and their isotypes were characterized. MAb 6B3-C5 was chosen as the detector antibody and conjugated with quantum dots. Based on MAb 6B3-C5 labeled with quantum dots, a modified dot blot assay was developed for the on-site determination of V. anguillarum. It was found that the method had no cross-reactivity with other than V. anguillarum bacteria. The detection limit (LOD) for V. anguillarum was 1 × 10³ CFU/ml in cultured bacterial suspension samples, which was a 100-fold higher sensitivity than the reported colloidal gold immunochromatographic test strip. When V. anguillarum was mixed with turbot tissue homogenates, the LOD was 1 × 10³ CFU/ml, suggesting that tissue homogenates did not influence the detection capabilities. Preenrichment with the tissue homogenates for 12 h could raise the LOD up to 1 × 10² CFU/ml, confirming the reliability of the method.

• 한국어병학회지
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• 제30권2호
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• pp.135-148
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• 2017

Pathogen introductions associated with aquatic invasive species threaten ecosystems and biodiversity worldwide. Bigheaded carps (BHC), including Silver Carp Hypophthalmichthys molitrix, Bighead Carp H. nobilis, and their hybrids, are prolific, invasive pests in central US rivers. However, little is known about pathogen effects on invading BHC or how BHC affect the disease risk profile for native fishes in receiving ecosystems. We therefore conducted, from May 2013-December 2014, a systematic pathogen survey for BHC and native fishes in the Wabash River watershed, Indiana, USA. We found Pseudomonas fluorescens, P. putida, and Salmonella enterica DNA in BHC as well as native fishes, although none of these bacteria were exclusively present in BHC. DNA from other bacterial taxa was detected only in native fishes and Common Carp Cyprinus carpio. No gastrointestinal helminths were detected in BHC, although they were common in most native fishes examined. We also conducted in vitro studies on BHC tissues (skin, gill, fin, and fry) and found high sensitivity to Largemouth Bass virus, viral hemorrhagic septicemia virus, and infectious pancreatic necrosis virus. We conclude that BHC are not heavily burdened by bacteria, viruses and parasites in the invaded study ecosystems, although they do harbor native bacteria and show potential for high sensitivity to endemic viruses.

• 한국수산과학회지
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• 제51권4호
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• pp.450-455
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• 2018

We examined correlations of the density of fish farms with the distributions of indicator bacteria (Escherichia coli, fecal streptococci) and a bacterial fish pathogen (Streptococcus parauberis) off the coastline of Jeju Island. Seawater samples were collected at four coastal sites on the Island [Aewol (control), Gujwa, Pyoseon and Daejeong] in June, August and October 2016. The indicator bacteria were generally more frequently isolated from samples taken in August when water temperatures and human activities on nearby beaches were highest. Although fish farms were least common at Daejeong, the numbers of isolated fecal indicator bacteria were highest in the seawater and effluent water collected from this site. Hence, fish farms were not likely major contributors of indicator bacteria at Daejeong. We found discrepancies between the isolated bacterial counts and the predicted bacterial copy numbers deduced from our qPCR results, indicating that this pathogen may exist in a viable but non-culturable (VBNC) state in seawater. Thus, livestock wastewater and chemical fertilizer loading off Jeju Island may negatively impact seawater quality more than the effluent released from fish farms does.

• 한국어병학회지
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• 제37권1호
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• pp.49-60
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• 2024

A viable but non-culturable (VBNC) state is a survival strategy adopted by bacteria when faced with unfavorable environmental conditions, rendering them unable to grow on nutrient agar while maintaining low metabolic activity. This study explored the impact of temperature and nutrient availability on inducing VBNC state in Edwardsiella piscicida, the most important bacterial fish pathogen, and assessed its pathogenicity at VBNC state. E. piscicida was suspended in filtered sterile seawater and exposed to three different temperatures (4, 10, and 25℃) to induce the VBNC state. Subsequently, the induced VBNC cells were subjected to resuscitation by either raising the temperature to 28℃ or inoculating them in brain heart infusion broth supplemented with 1% NaCl. A propidium monoazide (PMA)-qPCR method was also developed to selectively quantify live (VBNC or culturable) E. piscicida cells. The results showed that the bacteria entered the VBNC state after approximately 1 month at 4℃ and 25℃, and 2 months at 10℃. The VBNC E. piscicida cells were successfully revived within 3 days in a nutrient-rich environment at 28℃, highlighting the significance of temperature and nutrition in inducing and resuscitating the VBNC state. In pathogenicity tests, resuscitated E. piscicida cells exhibited high pathogenicity in olive flounder comparable to cultured bacteria, while VBNC cells showed no signs of infection, suggesting they are unlikely to resuscitate in fish. In conclusion, this study contributes to our understanding of fish pathogen ecology by investigating the characteristics of the VBNC state under varying temperature and nutrition conditions.

• 한국어병학회지
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• 제30권1호
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• pp.41-49
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• 2017

생균제는 성장촉진, 면역증진 및 질병예방에서 넙치 Paralichthys olivaceus 치어의 양식에서 우수한 생산효과로 적용될 수 있다. 성장률, 선천성면역 및 항병력을 증강시킬 수 있는 생균제의 효과를 조사하기위해 Bacillus subtilis, Bacillus licheniformis 및 Lactobacillus plantarum (BSL-LAB)이 혼합되어있는 생균제와 NBS (nitrifying bacteria con- sortium) 분말을 사료에 첨가 또는 수조에 투입하여 시험을 수행하였다. 생균제 첨가사료는 7주간 투여하였고 3가지의 생균제 조합 시험군 모두에서 넙치의 성장과 항병력에서 대조군에 비해 높은 유효성을 발휘 하였다. 어병세균에 대한 항병력의 긍정적인 결과는 생균제에 대한 면역기능의 향상으로 나타난 효과이며 상기 시험결과로 볼 때, 넙치치어 양식에서 생균제의 혼합첨가는 성장 및 선천성면역 뿐만 아니라 질병저항성에 좋은 효과를 나타낼 수 있을 것으로 사료된다.

• Journal of Microbiology and Biotechnology
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• 제25권4호
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• pp.511-520
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• 2015

Triclosan, the widely used biocide, specifically targets enoyl-acyl carrier protein reductase (ENR) in the bacterial fatty acid synthesis system. Although the fish pathogen Aeromonas salmonicida subsp. salmonicida exhibits triclosan resistance, the nature of this resistance has not been elucidated. Here, we aimed to characterize the triclosan resistance of A. salmonicida subsp. salmonicida causing furunculosis. The fosmid library of triclosan-resistant A. salmonicida subsp. salmonicida was constructed to select a fosmid clone showing triclosan resistance. With the fosmid clone showing triclosan resistance, a subsequent secondary library search resulted in the selection of subclone pTSR-1. DNA sequence analysis of pTSR-1 revealed the presence of a chromosomal-borne fabV-encoding ENR homolog. The ENR of A. salmonicida (FabVas) exhibited significant homology with previously known FabV, including the catalytic domain YX₍₈₎K. fabVas introduction into E. coli dramatically increased its resistance to triclosan. Heterologous expression of FabVas might functionally replace the triclosan-sensitive FabI in vivo to confer E. coli with triclosan resistance. A genome-wide search for fabVas homologs revealed the presence of an additional fabV gene (fabVas2) paralog in A. salmonicida strains and the fabVas orthologs from other gram-negative fish pathogens. Both of the potential FabV ENRs expressed similarly with or without triclosan supplement. This is the first report about the presence of two potential FabV ENRs in a single pathogenic bacterium. Our result suggests that triclosan-resistant ENRs are widely distributed in various bacteria in nature, and the wide use of this biocide can spread these triclosan-tolerant ENRs among fish pathogens and other pathogenic bacteria.

• 한국어병학회지
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• 제34권2호
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• pp.133-140
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• 2021

With the recent isolation of a new betanodavirus in shellfish, Korean Shellfish Nervous Necrosis Virus (KSNNV), it has also been identified the reassortant KSNNV of two RNA segments, in which one segment is KSNNV genotype but the other one is known genotype. In this study, we confirmed that the ressortant KSNNVs obtained in previous screening study of our laboratory for betanodaviruses in shellfish were KS/RGNNV and RG/KSNNV type by performing two consecutive multiplex RT-PCR on each RNA1 and RNA2 segment (R1- and R2-discriminative multiplex two-step RT-PCR, respectively) to determine the genotype of each segment based on the size of amplicon. In the pathogenicity analysis, none of the reassortants induced specific external symptoms or mortality of VNN, but viruses of 2 × 10⁴~10⁵ copies/mg or more were detected at 14 days after injection (10⁷ copies/fish) in brain tissues of 4 species except for crucian carp and common carp among the 6 species of juvenile fish used. In addition, the histopathological features of weak but distinct vacuole formation were also found in the brain of these infected fish, but no difference was found between the two reassortants KS/RGNNV-KG and RG/KSNNV-CM.

• 한국수산과학회지
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• 제52권5호
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• pp.539-546
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• 2019

The major cultured marine fishes in sea off the coast Gyeongsangnam-do Province, South Korea, were assessed and included 9.3% rockfish Sebastes schlegelii, 7.8% red seabream Pagrus major, and 2.1% rock bream Oplegnathus fasciatus. The number of insurance payments related to disease mortality in cultured fish in 2017 was fourfold that in 2016. Economic loss in aquaculture due to disease in cultured fish is high and represents an important inhibitory factor affecting marine fishery productivity. In 2018, diseases led to severe production losses in several aquaculture species: 40.0% in rockfish, 11.4% in olive flounder Paralichthys olivaceus, 10.0% in filefish Thamnaconus modestus, and 9.3% in red seabream. Fish-parasitic pathogens such as Microcotyle sebastis, Alella spp., and Dactylogyrus spp. enter mainly via the gills and skin surface. Among bacterial pathogens, Vibrio species were most common, with Vibrio harveyi being the dominant species causing infections in these fishes. The bacterium Lactococcus garvieae is thought to exhibit host specificity in fish. The fish species in the present study exhibited a higher tendency for infection by heterologous pathogens than by a single pathogen; therefore, it is necessary to devise new strategies for treating diseases in cultured fish.