• Journal of fish pathology
• /
• v.21 no.3
• /
• pp.247-257
• /
• 2008

To understand the activity of non-specific defence factors in cultured Sebastes, the antibacterial effect of the serum, skin mucus and homogenate of various organs from cultured oblong rockfish (Sebastes oblongus) and rockfish(Sebastes schlegeli) against pathogenic bacteria, Aeromonas hydrophila, Edwardsiella tarda, Vibrio anguillarum, and Streptococcus sp. was compared with that of flounder(Paralichthys olivaceus) and seabass(Leteolabrax japonicus). And the activities of proteolytic enzyme, chitinolytic enzyme and haemolycin as non-specific defence factor were investigated on the oblong rockfish and rockfish. Samples from oblong rockfish showed the highest antibacterial activity by lysoplate assay on agar plate mixed with pathogens, followed in descending order by rockfish, seabass, and flounder. Turbidimetric assay was carried to evaluate the lysozyme activity of fish samples against lyophilized cells of Micrococcus lysodeiktikus. The serum, kidney, liver, stomach, intestine and eyeball of oblong rockfish and the mucus and gill of rockfish appeared to have the highest lysozyme activity among the fish strains investigated. All samples except skin mucus, liver, and eyeball of oblong rockfish and rockfish showed proteolytic enzyme activity. Chitinolytic enzyme activity was showed in random sampling and haemolytic activity was remarkable in oblong rockfish. Therefore, Sebastes strain was proved to have effective defense mechanisms based on the antibacterial activities, and lysozyme, proteolytic enzyme, chitinolytic enzyme, and haemolycin were considered to act as the non-specific defence factor of Sebastes.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.57 no.1
• /
• pp.15-22
• /
• 2024

This study assessed microbial contamination in seven fried fish pastes sold in Southeast Asian traditional markets during summer. It measured viable cell count, coliforms, Escherichia coli, fungi, and Staphylococcus spp. It also qualitatively analyzed Vibrio parahaemolyticus, Salmonella spp., Bacillus cereus, Listeria monocytogenes, and Clostridium perfringens. The average viable cell count, coliforms and fungi were detected as 6.34 (3.84-8.13), 2.16 (1.00-3.55), and 3.92 (1.85-7.74) log₁₀ CFU/g, respectively. Staphylococcus spp. was detected at 4.59 (2.10-7.63) log₁₀ CFU/g. Some samples had high contamination levels: viable cell count (8.13 log₁₀ CFU/g), fungi (7.74 log₁₀ CFU/g) and S. aureus (7.63 log₁₀ CFU/g). However, E. coli was not detected in any samples (ND, <1 log₁₀ CFU/g). V. parahaemolyticus, Salmonella spp., B. cereus, L. monocytogenes, and Cl. perfringens were also not detected in the samples. The microbial contamination data provide insight into managing microbial contamination and ensuring the safety of fried fish pastes in traditional summer markets.

• Journal of fish pathology
• /
• v.32 no.2
• /
• pp.69-80
• /
• 2019

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.

• Journal of Marine Life Science
• /
• v.1 no.1
• /
• pp.18-24
• /
• 2016

Since April 2012, doctor fish in the breeding tank and in the quarantine tank in Hanwha Aquaplanet Yeosu Aquarium have been dying, accompanied by diffuse bleeding around the mouth, in the chin, and at the bottom of the abdomen. In this study, the cause of death would be examined through the bacteriological study of doctor fish and the rearing water quality in the aquarium. The water quality and the bacterial counts of the rearing water in the exhibit tank and in the quarantine tank were analyzed once a week, starting from August to November 2014. Water quality was measured based on the following data: temperature was in the range of 24.5~26.8℃, pH at 6.77~7.94, DO at 6.15~8.61 ppm, ammonia at 0~0.93 ppm, nitrite at 0.009~0.075 ppm, and nitrate at 1.1~40.9 ppm. Studies revealed that the differences in these water quality factors were not related to the death of doctor fish. Bacterial counts in the rearing waters of Garra rufa slightly increased to 10³~10⁴ CFU/ml, just before the death of the doctor fish. Twelve strains of bacteria were isolated from the dead fish and rearing waters. The isolates were identified as Aeromonas veronii, Citrobacter freundii, Pseudorhodoferax aquiterrae, Shewanella putrefaciens, and Vibrio anguillarum on the basis of 16S rRNA gene sequences. The most dominant species was C. freundii, which showed medium sensitivity to florfenicol and norfloxacin, and was resistant to amoxacillin, doxycycline, oxytetracycline, tetracycline, and trimethoprim. Ten isolates were confirmed to be pathogenic to the doctor fish. Doctor fish infected with C. freundii and S. putrefaciens showed high mortality in the experimental groups. These results indicate that the variation in bacterial numbers in the rearing water was related to the death of doctor fish. C. freundii and S. putrefaciens were directly implicated in causing the death of doctor fish in the aquarium.

• Korean Journal of Ichthyology
• /
• v.29 no.1
• /
• pp.41-51
• /
• 2017

To understand the application in farm for the fish aquaculture, we investigated biological and pathological traits on red sea bream Pagrus major which were reared in each copper-alloy net cage and the synthetic fiber net cage for 9 months. Two groups of cage were made and set in Yokji-eup, Tongyoung, Gyeongsangnam-do in size of 25 m in diameter and 10 m of depth. Survival rate of the red sea bream in the rearing copper-alloy net cage and synthetic fiber cage showed 99.75% and 99.70% respectively, there was no significant difference. Daily weight growth rate in each net was shown to 2.13 g/day and 1.65 g/day. Health analysis by blood composition analysis showed a favorable result in the copper-alloy net cage rather than in the synthetic fiber net. Bioaccumulation of heavy metal such as Cu and Zn especially in gonad was higher than other organ. Bioaccumulation of Cu and Zn in the muscle was lower compared to the permitted standard for food safety. Pathogenic infection test discovered Microcotyle tai for parasite, V. alginolyticus and other five species for bacteria. But there was a little bit difference of bacteria infection in copper-alloy net cage and copper-alloy net cage is expected to be has antibacterial effect. Thus, copper-alloy net cage can be applied to farm considering its system stability, recycling, antibiosis and food safety.

• Journal of fish pathology
• /
• v.4 no.2
• /
• pp.87-94
• /
• 1991

In the late summer of 1990 and 1991, mass mortality occured among cage-cultured grouper, Epinephelus septemfasciatus in south cost of Korea. The moribund fish didn't feed and became pale or dark chestnut colour and irregularly swimmed due to the loss of equilibrium, finally the diseased fish fell down side away on the bottom or the surface of cage showing the bent of body and died. The diseased fish showed the extensive hemorrahge in brain, the swelling of spleen and bile duct as the specific syptoms of internal organs. So the gill, skin and other organs of the diseased fish were examined for the presence of pathogenic parasites and bacteria. The parasitic Trichodina sp. were detected only from the gill lamella of the diseased fish, but these parasites seemed to be not a direct causative agents that induced the gross mortality of the cultured grouper. because these parasites were also observed in normal grouper, yellowtail, red seabream and rock bream co-cultured with the diseased grouper in same or near cages. In the viral examination, although isolation of the causative agent by the use of estabilshed cell Lines, RTG-2 and CHSE-214, was not succeed, the normal grouper inoculated intramuscularly with the filtered homogenate of the organs of the diseased fish showed the same external and internal signs with the naturally infected grouper. They died within a week. By using the naturally and the artificially infected fishes, electron microscopic observation revealed numerous hexagonal or polygonal particles in the cytoplasm of liver cells. Based on the these results, we suggest that the mass mortality of the cultured grouper would be occurred by the infection of a viral agent.

• Journal of fish pathology
• /
• v.24 no.3
• /
• pp.213-223
• /
• 2011

Among wild marbled sole, Pleuronectes yokohamae caught in west coastal area, Chungnam, tumor-bearing fish were found. Parasites and pathogenic bacteria were not detected and CPE was not observed. Using the light microscope, the epidermal layer of wild P. yokohamae was significantly thickened compared to the normal skin. The lesion was formed papillary folds. Hypertropical epithelial cells revealed karyolysis, marked nucleolus and cloud swelled cytoplasm. In the epidermal layer of the lesion, X-cell that is characterized by oval and small pale nucleus and prominent nucleolus was observed. Dermal layer had newly formed vessels. The size of mucous cell in the papilloma lesion was significantly increased compared to the normal. In this study, no pathogens were found, so future works for finding cause of the papilloma in the P. yokohamae are needed.

• Journal of fish pathology
• /
• v.32 no.2
• /
• pp.97-104
• /
• 2019

The purpose of this study was to investigate the antimicrobial resistance and resistance transfer of Vibrio parahaemolyticus and Morganella morganii isolated from fish products purchased from fish markets in Yeosu April - December 2017. These bacteria were identified by biochemical test and PCR results, and the transfer of antimicrobial resistance was confirmed by the broth mating method. To isolate the transconjugants formed during conjugation, TSA medium containing 50 ㎍/ml of ampicillin (AMP), and 150 ㎍/ml of streptomycin (SM) or 30 ㎍/ml of oxytetracycline (OT) was used. M. morganii isolates showed low susceptibility to AMP, amoxicillin (AML), and colistin (CT), erythromycin, OT, and tetracycline, compared to V. parahaemolyticus resistance to AMP, AML, and CT. The conjugation of V. parahaemolyticus or M. morganii with Escherichia coli resulted in the separation of V. parahaemolyticus and M. morganii showing SM resistance as transconjugants. Meanwhile, Edwardsiella tarda transconjugants showing AMP and AML resistance were obtained from the broth mating of V. parahaemolyticus and E. tarda. But the transfer of the VPA0477 which is a β-lactamase gene of V. parahaemolyticus was not confirmed. These results suggest that resistance transfer between pathogenic bacteria is bidirectional and progresses in a wide variety of patterns.

• Journal of fish pathology
• /
• v.6 no.2
• /
• pp.205-218
• /
• 1993

On the development of hirame(Paratichtys olivaceus) culture, outbreak of scuticociliata infection was reported to cause severe damage in Japan. To establish effective measures for isolation and cultivation of this ciliate, we tried to culture this pathogenic ciliate using medium for bacteria and fish cell lines in vitro. Scuticociliata from the brain tissues of infected fish was aseptically inoculated to CHSE-214 cells cultured in MEM-10 without antibiotic. Scuticociliata grew well and the number of ciliate reached $10^6\;cells/ml$ at temperatures of $15^{\circ}C$ to $20^{\circ}C$ for 10d. The number of ciliate cultured in the cell lines is 10 times higher than the numbers cultured in the liquid medium alone. This ciliata could be cloned by dilution method. Scuticociliata isolated could grow well on 42 different cell lines that were established from marine fish, warm freshwater fish, and salmonids. This ciliate could be preserved in liquid nitrogen for more than 6 months. Subsequently, we observed the optimal temperature and salinity for growth, and tested the sensitivities of this organism to formaldehyde, flagyl(Metronidazole), Ekuteshin(Combination compound of sulfamonometoxin and ormethoprim), and ozonixation. Optimal temperature for growth was $25^{\circ}C$ and salinity was 1.0 to 1.5%. Washed scuticociliata was killed by formaldehyde at the concentration of 50ppm for 10min, but was not completely killed even at a high concentration of 400ppm for 20min in MEM-5. Flagyl and Ekuteshin can inhibit the growth of scuticociliata at the concentration of 1,000 and $100{\mu}g/ml$ in MEM-10, respectively. More than 99% of this scuticociliata could be killed by ozonization at a dose equivalent to $1.0mg/\ell$ oxidant for 30sec in sea water. Isolated scuticociliata showed the pathogenicity to the cultured hirame by artificial infection(I. P. injection, $10^5\;cells$/fish). The number of scuticociliata in the water could be counted by most probable number(MPN) method using tissue culture, and the minimum detectable number was $1.8\;cells/\ell$. The number in the reservoir tank for water supply to the culture tank was 110 cells/l. After cleaning by elimination of the sediments from of the reservoir tank and disinfected with formaldehyde, number of scuticociliata decreased and was counted less than $1.8\;cells/\ell$ and infection rate of cultured hirame was decreased.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.19 no.2
• /
• pp.147-154
• /
• 1986

Vibriosis has caused severe losses among cultured yellowtail (Seriola quinquerediata) at some cage farms in Korea in recent years. Major object of this study was to investigate the causative organism of the diseased cultured yellowtail. The samples were collected from the aquarium of Fisheries Research & Development Agency during the period from November 1984 to January 1985. The experimental results are summarized as follows ; Among the isolated bacteria from the diseased yellowtail, Vibrio sp. isolated from the kidney was considered to he the causative organism. Tetracycline, chloramphenicol and gentamycin were observed as bacteriostatic agents to the pathogenic strain, but sulfisomezole and sulfisoxasole were not. When the isolated strain was injected intramuscularly to yellowtail, rid sea-bream, rock-bream and common carp, it had virulence at $25^{\circ}C$ to all fish examined but to virulence at $15^{\circ}C$ except for yellowtail.