본 연구에서는 2012년부터 2018년 1월까지 국내 어류에서 참돔이리도바이러스병 (red sea bream iridoviral disease; RSIVD) 으로 확정 진단된 주요 분리주에 대하여 major capsid protein (MCP) 유전자의 염기서열을 바탕으로 Megalocytivirus의 유전적 관계를 명확히 했다. 또한, Megalocytivirus와 숙주 세포간 상호작용에 영향을 줄 수 있는 특이 유전자 2종, Vascular endothelial growth factor (VEGF) 및 Histidine triad motif인 HIT-like 단백질 (HIT)에 대한 염기서열 분석을 통해 유전적 상관관계를 고찰하였다. 국내 어류에서 분리된 39개의 megalocytiviruses는 2가지 유전형인 red sea bream iridovirus (RSIV)형과 turbot reddish body iridovirus (TRBIV)형으로 분류되었으며, RSIV형의 megalocytiviruses는 다시 유전아형인 RSIV-subgroup 1형과 2형으로 분류되었다. 그리고 VEGF 유전자 염기서열 분석 결과에서는 RSIV형의 바이러스에서 변이가 발생되었음을 확인할 수 있었으며, HIT-like 단백질 유전자는 RSIV형의 Megalocytivi rus에서만 발견되는 것을 알 수 있었다.

본 연구에서는 넙치(Paralichthys olivaceus)로부터 분리한 바이러스성출혈성패혈증바이러스(viral hemorrhagic septicemia virus, VHSV, genotype IVa)에 대한 단클론 항체(monoclonal antibody, MAb)를 개발하였다. VHSV에 대한 항체를 생산하는 총 5개의 hybridoma clone을 생산하였다. 4개의 MAbs (2C10, 18H4, 23H6, 30B7)는 glycoprotein을 인식하였고, MAb 15E10은 nucleocapsid protein을 인식하였다. 5개의 MAbs는 western blot 상에서 VHSV에 감염된 세포와 넙치시료에 반응하였으나, 정상 세포와 넙치시료에는 반응하지 않았다. 또한 ELISA상에서 VHSV에만 반응하였고 6종의 어류바이러스(IHNV, HIRRV, SVCV, IPNV, MABV, NNV)에는 반응하지 않았다. 이상의 결과, 본 연구에서 제작된 MAbs는 VHSV에만 특이적으로 반응하는 것이 확인되어 VHSV를 검사하는데 사용될 수 있을 것으로 사료된다.

We performed MLSA (multilocus sequence analysis) and phenotypic characterization of Aliivibrio species isolated from walleye pollock (Gadus chalcogrammus) maintained in 3 different facilities of Gangwon Province, the east coast of Korea. Of 38 Aliivibrio species identified by 16S rDNA sequences, 12 strains were randomly selected and MLSA was conducted with 5 house-keeping genes (gapA, gyrB, pyrH, recA and rpoA) and 16S rDNA gene. Phylogenetic analysis and homology of the concatenated sequences (4,580 bp) with other Vibrionaceae genera revealed that 4 strains (GNGc16.1, YYGc16.1, YYGc16.2, GSGc18.1) were identified as Aliivibrio logei and one strain (GSGc16.1) as A. wodanis. One strain (GSGc17.1) was tentatively identified as A. logei, but needs further analysis because it did not belong to the same clade with A. logei type strain. 6 strains (GSGc17.2, GNGc16.2, GSGc16.2, GSGc17.3, GSGc18.2, GSGc17.4) need further investigation as potential novel species. Either phenotypic characterization or 16S rDNA sequence alone did not provide enough information for identification of Aliivibrio strains at the species level. A. logei and A. wodanis are generally known as non-pathogenic bacteria, but also known as opportunistic or secondary pathogens of cold water fishes. Cares should be taken to prevent potential outbreaks due to these bacteria, although there was no outbreaks during the sampling period.

As an epidemiological survey, mortality of marbled rockfish, Sebastiscus tertius observed from a fish farm in Gyeongnam province of South Korea. The major macroscopic sign of the diseased fish was severe multifocal dermal ulceration. Histological observation revealed inflammation, necrosis and colonization of bacteria in various tissues (gill, liver, spleen and kidney). Bacteria was isolated from spleen and kidney in moribund and mortality fish. Seven bacterial isolates from the diseased fish were identified as Aeromonas salmonicida subsp. salmonicida using API 20E and 20NE, API 50CH API ZYM system. Under light microscopy, infected marbled rockfish showed the lifting of the lamella epidermal layer, edematous changes and hypertrophy of epithelial cell in the gill filament. The atrophy of the mucosal fold, erythema in the intestine, and the necrosis of hematopoietic tissue and renal tubule cells with karyolysis were observed in the kidney. In this study was demonstrated the histological reaction of red marbled rockfish infected by Aeromonas salmonicida. Furthermore, this is the first account of extensive dermatitis in Sebastiscus tertius due to atypical A. salmonicida infection, which has high potential in aquaculture among native fish species.

Rainbow trout (Oncorhynchus mykiss) were treated with ultrasonic (40kHz) and microbubble. The organic serum components, glucose were decreased compared to control at microbubble single treatment (M) and ultrasonic treatment (UL), but glucose concentrations in fish serum of all experimental groups analyzed in this study were also within the normal range. The organic serum components, cholesterol and total protein were no significant change by ultrasonic and microbubble treatment. There were no significant changes in the lysozyme activity on ultrasonic and microbubble treatment. Serum bactericidal activity decreased on ultrasonic single treatment (UL) compared to the control (P<0.05), but the numbers of bacterial colonies were significantly lower than those in the negative (PBS). The results of this study indicate that ultrasonic and microbubble treatment did not have a critical effect on the serum composition and innate immunity of O. mykiss, and that it is a way to do not significant stress on the fish body as a countermeasure against sea lice.

본 연구에서는 2017년 4월부터 12월 사이에 여수수산시장에서 구입한 수산물로부터 분리된 Vibrio parahaemolyticus와 Morganella morganii의 내성특성을 알아보고 장내세균인 Escherichia coli와 어류 병원균인 Edwardsiella tarda와의 내성전이 가능성을 알아보았다. Broth mating 법으로 실시한 conjugation에서 형성된 transconjugants를 분리하기 위하여 ampicillin(AMP) 50 ㎍/ml와 streptomycin (SM) 150 ㎍/ml 또는 oxytetracycline(OT) 30 ㎍/ml이 첨가된 TSA배지를 사용하였다. AMP, amoxicillin (AML), colistin(CT)에 낮은 감수성을 보였던 V. parahaemolyticus와 달리 M. morganii는 AMP, AML, CT, erythromycin, OT, tetracyclin등에 감수성이 낮았다. V. parahaemolyticus와 M. morganii를 E. coli와 conjugation을 실시한 결과 transconjugants인 E. coli는 분리되지 않은 반면 SM내성을 획득한 V. parahaemolyticus와 M. morganii가 분리되었다. 한편 V. parahaemolyticus와 E. tarda의 broth mating에서는 AMP와 AML 내성을 획득한 E. tarda transconjugant가 분리되었다. 그러나 V. parahaemolyticus의 β-lactamase 유전자인 VPA 0477의 전이는 확인되지 않았으며, E. tarda의 내성이 전달된 V. parahaemolyticus나 M. morganii는 검출되지 않았다. 이와 같은 결과는 생물 위해성 세균들 간의 내성전이가 양방향성이며 매우 다양한 패턴으로 진행되고 있음을 시사한다.

Citurs unshiu Markovich is a medicinal product of dried tangerine peel (DTP). It is effective on antioxidation, and getting fame as a medicine and functional food. By utilizing DTP as a feed additive, we aim to enhance the growth rate, innate immunity, and bacterial infection resistance to Tilapia. The DTP extract was added to the feed weight by 0.1, 0.5, 1, 5% and then fed to tilapia for 7 days to evaluate the innate immunity parameter, growth rate and anti-bacterial activity. Innate immunity parameter results showed that the ROI was significantly higher in the 5% group added at high concentration, while showing decrease or no differences in other experimental groups. In other parameters, all the experimental groups showed no significant difference or decreased compared to the control group. The challenge test showed a high survival rate of 71% in the 0.5% group and the lowest in the control group (36%). For the growth rate, the feed efficiency was improved in all groups except for the 0.1% group compared to the control group. In conclusion, DTP extract has bacterial resistant effect in while not affecting innate immune system of fish. Also, it has shown the potential as a possible feed additive as it has brought the improvement on feed efficiency ratio.

Effects on glutathione-related antioxidant parameters were examined after a chronic exposure of olive flounder, Paralichthys olivaceus to dietary 4-tert-octylphenol (4-tert-OP). Fish were fed diets containing 4-tert-OP at 0, 1, 5 and 10 mg/kg diet for 6 weeks. Antioxidant parameters examined were reduced glutathione (GSH) contents and enzyme activities of glutathione reductase (GR), glutathione S-transferase (GST) and glutathione peroxidase (GPx) in tissue homogenates of the liver, kidney and gill. It was observed that all parameters examined increased although there were some differences in dose responses and temporal patterns in the increase. GSH contents increased after exposure to 4-tert-OP in the three organs examined. However, the GSH increase was evident only after 4 weeks in the liver whereas it was elevated after 2 weeks in the kidney and gill. GR activity exhibited a significant increase in response to 4-tert-OP at 1 mg/kg in all three organs, however, its activity returned to control levels when exposed to 5 and 10 mg/kg. Hepatic GST activity showed an earlier increase at week 2 in contrast to the kidney and gill where they increased after 4 weeks of 4-tert-OP exposure. Temporal patterns in GPx activity changes to 4-tert-OP exposure were dissimilar among the organs: hepatic activity increased from week 2 through week 6; renal activity increased transiently at week 2; gill levels were higher through weeks 4 - 6. The results suggest that elevation of several GSH-related antioxidant parameters can be considered as evaluation criteria for 4-tert-OP-induced oxidative stress in a fish.

In this study, white spots appearing in carapace of imported white leg shrimp Litopenaeus vannamei were observed by macroscopic and microscopic examination. White spots due to white spot disease showed two types, white spots with a regular circular shape ranging from 0.4 mm to 1.7 mm and white spots with an irregular shape ranging from 0.05 mm to 2 mm. White spots due to other causes showed four types that appeared as crystalized materials in range of 100 ㎛ around the tegumental gland, as polygonal inorganic deposits ranging from 58 ㎛ to 188 ㎛, as Linear inorganic deposits ranging from 0.8 mm to 9 mm, as brownish spots ranging from 0.1 mm to 0.4 mm, and brownish spots containing melanin ranging from 0.1 mm to 2 mm. As a result, white spots occurred in imported white leg shrimp Litopenaeus vannamei were divide two type, due to white spot disease or other causes, for quarantine works.