• 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.37 no.1
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• pp.61-69
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• 2024

In this study, bacterial disease monitoring was conducted from July to November 2022 for three representative bacterial species (Streptococcus parauberis, Vibrio spp. and Edwardsiella piscicida) to investigate the occurrence of bacterial diseases in farmed olive flounder (Paralichthys olivaceus) on Jeju. Over a period of five months, 3,146 olive flounders were tested. The average length and weight of the olive flounder that were sampled for the disease were found to be 32.1 cm and 357.9 g, respectively. Bacteria were detected in 1,228 olive flounders, of which 24.6% were identified as Vibrio spp.. S. parauberis and E. piscicida were identified in 6.3% and 3.2% respectively, and 3% were unknown strains that could not be identified. Also, 41 (1.3%) olive flounders were found to have both S. parauberis and Vibrio spp. and 23 (0.7%) olive flounders were found to have both E. piscicida and Vibrio spp.. In particular, S. parauberis, Vibrio spp. (V. scophthalmi) and E. piscicida were detected simultaneously in one olive flounder. In fish infected with E. piscicida, the most obvious external signs were hernias and ascites.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.4
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• pp.397-403
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• 2018

We determined the resistance rates of pathogenic bacteria isolated from cultured olive flounder Paralichthys olivaceus to erythromycin (Em), antibiotic typically used in aquaculture and analyzed the genotypes of resistant bacteria using polymerase chain reaction (PCR). We isolated and utilized 160 isolates of Streptococcus parauberis, 1 of S. iniae, 66 of Edwardsiella tarda, 56 of Vibrio sp. and 23 of unidentified bacteria from presumed infected olive flounder from Jeju Island from March 2016 to October 2017. Of the 306 isolated strains, Em-resistant strains included 33 of S. parauberis, 39 of E. tarda and 2 of Vibrio sp. We conducted PCR to assess the resistance determination of Em-resistant strains. Five different types of Em-resistance genes were detected in the 74 Em-resistant strains: erm (A), erm (B), erm (C), mef (A) and mef (E); erm (A) and erm (B) were detected in 1 (3%) and 24 (72.7%) S. parauberis isolates, respectively. In E. tarda, erm (B) was detected in five isolates (12.8 %) and no Em-resistance genes were detected in the two Vibrio sp. isolates.

• Microbiology and Biotechnology Letters
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• v.50 no.3
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• pp.347-353
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• 2022

In this study, the effect of a synbiotic mixture of probiotics and 3% inulin on the growth, non-specific immune response, and mortality due to disease resistance of Paralichthys olivaceus was investigated. The results revealed that an 8-week diet of synbiotic-added feed, had no significant effect on the growth of P. olivaceus, Analysis of the hematological parameters revealed that there was a significant difference in the content of AST, total protein, and cholesterol among the groups, whereas there was no significant difference in the ALT and glucose contents. Further, there was no significant difference in the lysozyme activity of the synbiotic and control group after 8 weeks' feeding. In addition, when the symbiotic mixture was used rather than probiotics alone, the NBT activity of the synbiotic group increased compared to that of the control group. Moreover, when only probiotics were used, the cytokine expression in the spleen of the samples was significantly lower than that in the control group, whereas the expression was significantly higher in the spleen of the synbiotics group. However, there was no significant difference in the cytokine expression in the liver, intestine, and kidney of the three groups. Lastly, after injection for 2 weeks, the mortality rates of the control group towards Edwardsiella tarda, Streptococcus parauberis, and Streptococcus iniae were 95, 85 and 85%, respectively; those of the probiotics group were 85, 80, and 80%, respectively; and those of the synbiotics group were 80, 80, and 85%, respectively.

• 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.

• Journal of Fisheries and Marine Sciences Education
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• v.29 no.3
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• pp.834-846
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• 2017

Aquaculture practices to ensure greater production, such as high density breeding and excessive feeding, are become stressors that raise the prevalence of diseases. Accordingly, increasingly large volumes of antibiotics are used more frequently each year. Long term use antibiotics can generate resistant bacteria, which interrupt treatments and cause a potential transfer to human bodies. Thus, antibiotic resistance is of importance in public health. Tetracycline (Tc) is one of the typical medicines used in the aquaculture drugs, which has a wide range of application including gram-positive and gram-negative bacteria. In the examination of 153 strains isolated from olive flounder (Paralichthys olivaceus) farms located in Jeju in 2016, it turned out that a total of 84 strains were resistant to Tc or oxytetracycline (OTC). The extent to which the strains are resistant to Tc and OTC was confirmed through MIC test, mostly within the range of 25 to $100{\mu}g/m{\ell}$. Twelve different types of tet genes were detected using single and multiplex PCR in the 84 Tc-resistant strains. The PCR was used to find tet(K), tet(M), tet(O), and tet(S), which are known to exist primarily in gram positive strains. According to the results, - tet(S) is the most dominant gene in 49 strains of Streptococcus parauberis, accounting for 63.2%. And there were two strains that have two different types of resistant genes. The multiplex PCR was used to detect tet(A), tet(B), tet(C), tet(D), tet(E), and tet(G), which are commonly found in gram-negative strains. Each of tet(B), tet(D), and tet(B)&(M) was found in a strain presumed to be Vibrio sp., and only tet(D) was found in 10 Edwardsiella tarda strains.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.4
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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.

• Korean Journal of Veterinary Service
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• v.45 no.3
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• pp.181-189
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• 2022

Streptococcus is one of the major pathogen groups inducing bovine mastitis. The aim of this study was to investigate the antimicrobial resistance patterns of Streptococcus species isolated from bovine mastitis milk samples in Korea from 2016 to 2021. In total, 181 (10.3%) Streptococcal isolates were collected from 1,761 quarter milk samples at 122 farms; S. uberis 39.2% (n=71), S. dysgalactiae 29.3% (n=53), S. equinus 9.9% (n=18), S. suis 6.1% (n=11), S. parauberis 4.4% (n=8), S. lutetiensis 3.9% (n=7), others 7.2% (n=13). However, S. agalactiae was not isolated. The isolates showed the highest resistance rate to tetracycline (55.2%) followed by erythromycin (45.3%) and pirlimycin (36.5%). In contrast, all isolates were susceptible to ceftiofur, cephalothin, penicillin/novobiocin, and only single S. equinus isolate was resistant to both ampicillin and penicillin. Of 181 isolates, 64 (35.4%) were multidrug resistance (MDR). The resistance to pirlimycin of S. uberis (73.2%) was much higher than that of other species (0~36.4%). All S. suis isolates were resistance to tetracycline. S. dysgalactiae showed lower resistance to erythromycin, pirlimycin and tetracycline than S. uberis and S. suis. The rate of MDR was relatively higher among S. uberis (73.2%) than among S. suis (36.4%), S. dysgalactiae (15.1%), others (0%). In conclusion, antimicrobial resistance in Streptococcus spp. should be regularly examined for appropriate therapies because the resistance patterns were various among the individual species.

• Journal of fish pathology
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• v.33 no.1
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• pp.91-95
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• 2020

Fish bacterial diseases have spread and caused serious problem for cultured marine fish in Korea. The important bacterial disease affecting mariculture such as olive flounder (Paralichthys olivaceus) are caused by Edwardsiella tarda, Vibrio scophthalmi and Streptococcus parauberis. For the bacterial disease protection in aquaculture industry, the water treatment is needed in aquaculture system. During the last decades atmospheric pressure non-thermal plasma in contact with liquids have received a lot of attention of environmental and medical application. In this study, we determined the disinfectant effect in seawater and three major fish bacterial disease pathogens by using low frequency plasma treatment. Three fish bacteria (E. tarda, V. schophthalmi, S. parauberis) were not detected within 16 min, 150 min and 270 min of 20 L, 500 L and 1 ton seawater post low frequency plasma treatment, respectively. Three major fish bacterial disease pathogens were not detected within 2 min after the low frequency plasma treatment, suggesting that the low frequency plasma possess disinfectant effectiveness.