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Streptococcus parauberis의 디스크 확산법 결과에 대한 Epidemiological Cut-off Value의 설정
천원경,이윤항,김윤재,노형진,김아란,김남은,서정수,권문경,이지훈,김도형 한국수산과학회 2019 한국수산과학회지 Vol.52 No.4
Streptococcosis caused by Streptococcus parauberis is a very important disease in farmed olive flounder Paralichthys olivaceus. For most fish pathogens, including S. parauberis, there are no analytical criteria to distinguish antibioticsusceptible strains from antibiotic-resistant strains. In this study, epidemiological cut-off (COWT) values were generated to classify 75 strains of S. parauberis isolated from 1999 to 2018 as wild type (WT) and non-wild type (NWT) using disc diffusion data and normalized resistance interpretation (NRI) analysis. The susceptibility of the isolates to 16 antibiotics was evaluated using CLSI guideline M42-A. The wild-type cut-off values for amoxicillin, erythromycin, oxytetracycline, and florfenicol for S. parauberis were ≥ 35, 31, 28, and 27 mm, respectively. The NWT ratios of S. parauberis strains to treatment with GEN, FFC, ENR, SXT, EFT, VAN, and CHL were 17% or less, indicating that these antibiotics may be used to treat streptococcosis caused by S. parauberis. For recent S. parauberis isolates, the NWT ratios for AMX, ERY, OTC and FFC are much higher than for strains isolated from 1999-2007. The COWT data from this study will assist aquatic animal disease professionals in prescribing appropriate antibiotics for the treatment of streptococcosis caused by S. parauberis, which will help reduce the misuse and abuse of antibiotics in the aquaculture sector.
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난배양성(viable but non-culturable; VBNC) Edwardsiella piscicida의 특성 연구
김아현,이윤항,노형진,허영웅,김남은,김도형 한국어병학회 2024 한국어병학회지 Vol.37 No.1
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 avail-ability 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°C) to induce the VBNC state. Subsequently, the induced VBNC cells were subjected to resuscitation by either raising the temperature to 28°C 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°C and 25°C, and 2 months at 10°C. The VBNC E. piscicida cells were successfully revived within 3 days in a nutrient-rich environment at 28°C, 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.
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포르말린과 청색 LED 병용처리에 의한 항스쿠티카 효과
강문경,이주엽,이윤항,김도형,Kang, Mun-Gyeong,Lee, Ju-Yeop,Lee, Yoonhang,Kim, Do-Hyung 한국어병학회 2022 한국어병학회지 Vol.35 No.1
Scuticociliatosis caused by Miamiensis avidus is a very important parasitic disease in olive flounder farming industry. The aim of this study was to determine effect of combined treatment with blue LED (light-emitting diode) illumination and formalin on olive flounder (Paralichthys olivaceus) infected with M. avidus. Different intensity of 405 nm LED (20, 40, and 60 μmol·m<sup>-2</sup>·s<sup>-1</sup>) was illuminated on 2.2×10<sup>4</sup> cells/well of M. avidus in a 24 well microplate for 24 h. Also, 2.4×10<sup>4</sup> cells/well of M. avidus were exposed to varying combinations of 60 μmol·m<sup>-2</sup>·s<sup>-1</sup> of 405 nm LED and serial 10-fold dilutions of formalin (from 10 to 100 ppm) for 15, 30, 45, and 60 min. Surviving M. avidus were counted using a hemocytometer. For in vivo test, flounder acclimatized at 11-12 practical salinity unit (psu) were challenged with 2×10<sup>6</sup> cells/ml of M. avidus by immersion method for 1 h. Then, fish were moved and divided into four groups; "F" group, treated with formalin at 50 ppm; "L" group, treated with 60 μmol·m<sup>-2</sup>·s<sup>-1</sup> of 405 nm LED; "C" group, treated with combination of the two methods; and the control group. After treatment for 30 min, fish were transferred to new tanks (salinity = 11-12 psu) and observed for 3 weeks. As a result, illumination of 405 nm LED at 60 μmol·m<sup>-2</sup>·s<sup>-1</sup> killed 100% of M. avidus after 12 h, while 67% and 90% of the scuticociliate died at 20 and 40 μmol·m<sup>-2</sup>·s<sup>-1</sup>, respectively, after 24 h exposure. One hundred percent of M. avidus was killed at 90, 80, 80 and 70 ppm after exposure to formalin for 15, 30, 45 and 60 min, respectively. However, combined method (e.g., 60 μmol·m<sup>-2</sup>·s<sup>-1</sup> of 405 nm-LED plus 50 ppm formalin) killed the parasite within 30 min. From in vivo test, similarly, survival rates of fish challenged with M. avidus were 100%, 43%, 29% and 0% in the C, F, L, and control groups, respectively. Results obtained in this study demonstrates that the combined treatment method has clear synergistic effect on scuticociliatosis in fish.
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2017년 동해안권역과 제주도권역 양식장 주변 해역의 오염지표세균의 분포
노형진,김남은,천원경,김아란,이윤항,김영재,황지연,김도형 한국수산과학회 2018 한국수산과학회지 Vol.51 No.6
In 2017, total coliform (TC), fecal coliform (FC) and fecal Streptococci (FS) bacteria were examined in seawater samples collected at coastal sites on Jeju Island (Aewol as a control, Namwon, and Daejeong) and at Pohang (Yeongil as a control, Guryongpo-North, and Guryongpo-South) to examine the correlations between the density of fish farms and distributions of the indicator bacteria. Only a few TC, FC, and FS colonies were detected in all of the samples obtained from Jeju Island. Of note, 2,000 and 1,000 CFU of FS 100 mL-1 were detected in samples from Guryongpo- South in June and August, respectively. Although the total area of approved fish farms located within 5 km of the sampling point at Guryongpo-South is 5-16 times smaller than in other regions, the number of indicator bacteria was highest in this region. Therefore, microbiological pollution in the Guryongpo-South region might be due to sources other than the effluent released from nearby fish farms.
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