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Characterization and Pathogenicity of Flavobacterium psychrophilum Isolated from Rainbow Trout (Oncorhynchus mykiss) in Korea

Flavobacterium psychrophilum is the causative agent of bacterial cold-water disease in salmonids and rainbow trout fry syndrome. This pathogen has attained a global presence and can spread both horizontally and vertically. However, it was not documented in Korea before September 2018. In this study,...

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Autores principales: Park, Jiyeon, Roh, HyeongJin, Lee, Yoonhang, Lee, Ju-Yeop, Kang, Hyo-Young, Seong, Min Ji, Kang, Yura, Heo, Young Ung, Kim, Bo Seong, Park, Chan-Il, Kim, Do-Hyung
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10609541/
https://www.ncbi.nlm.nih.gov/pubmed/37894203
http://dx.doi.org/10.3390/microorganisms11102546
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author Park, Jiyeon
Roh, HyeongJin
Lee, Yoonhang
Lee, Ju-Yeop
Kang, Hyo-Young
Seong, Min Ji
Kang, Yura
Heo, Young Ung
Kim, Bo Seong
Park, Chan-Il
Kim, Do-Hyung
author_facet Park, Jiyeon
Roh, HyeongJin
Lee, Yoonhang
Lee, Ju-Yeop
Kang, Hyo-Young
Seong, Min Ji
Kang, Yura
Heo, Young Ung
Kim, Bo Seong
Park, Chan-Il
Kim, Do-Hyung
author_sort Park, Jiyeon
collection PubMed
description Flavobacterium psychrophilum is the causative agent of bacterial cold-water disease in salmonids and rainbow trout fry syndrome. This pathogen has attained a global presence and can spread both horizontally and vertically. However, it was not documented in Korea before September 2018. In this study, the objectives were to characterize Flavobacterium psychrophilum strain FPRT1, isolated from diseased rainbow trout genotypically and phenotypically. We also conducted various investigations to better understand its impact and assess potential control measures. We acquired fifty rainbow trout (approximately 70 g in weight) and transferred them to a laboratory aquarium. During the initial acclimation period, we observed mortality and examined affected fish for clinical signs. We isolated the bacterium from the spleen of infected rainbow trout using tryptone yeast extract salts agar supplemented with glucose, naming this FPRT1. Antibiotic susceptibility testing was carried out, and from the result, we selected enrofloxacin to administer to the trout orally to reduce mortality. To evaluate pathogenicity, we exposed the trout to FPRT1 at different water temperatures (8, 15, and 22 °C). Genomic analysis was conducted to identify the serotype and relatedness of FPRT1 to European strains. Affected fish displayed clinical signs, such as ulcerative lesions in the mandible, anemia with pale gills, exophthalmia, and increased mucus secretion. Internal symptoms included pale liver and enlarged spleen. FPRT1 was susceptible to erythromycin, enrofloxacin, florfenicol, oxytetracycline, and gentamicin, but resistant to oxolinic acid and sulfamethoxazole/trimethoprim. Oral administration of enrofloxacin resulted in a decrease in mortality from 28% to 6%. Pathogenicity tests revealed varying mortality rates due to FPRT1 at different temperatures. The highest rates were observed at 8 °C (ranging from 43% to 100%) for both intraperitoneal and intramuscular injections, and lower rates occurred at 22 °C (ranging from 0% to 30%), with intramuscular injections displaying higher susceptibility. Genomic analysis identified FPRT1 as serotype 2 and indicated its close genetic relationship with European strains based on the core genome and dispensable genome. The substantial genomic similarity between our strain and European strains suggests the possibility of bacterial spread through the importation of fertilized eggs from Europe. In conclusion, this study highlights the introduction of the previously undocumented pathogen (F. psychrophilum) into Korean rainbow trout populations. The detection of this pathogen and its pathogenicity assessment is not only important for understanding its impact on local aquaculture but also for establishing surveillance and control measures to prevent further transmission and outbreaks in the region.
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spelling pubmed-106095412023-10-28 Characterization and Pathogenicity of Flavobacterium psychrophilum Isolated from Rainbow Trout (Oncorhynchus mykiss) in Korea Park, Jiyeon Roh, HyeongJin Lee, Yoonhang Lee, Ju-Yeop Kang, Hyo-Young Seong, Min Ji Kang, Yura Heo, Young Ung Kim, Bo Seong Park, Chan-Il Kim, Do-Hyung Microorganisms Article Flavobacterium psychrophilum is the causative agent of bacterial cold-water disease in salmonids and rainbow trout fry syndrome. This pathogen has attained a global presence and can spread both horizontally and vertically. However, it was not documented in Korea before September 2018. In this study, the objectives were to characterize Flavobacterium psychrophilum strain FPRT1, isolated from diseased rainbow trout genotypically and phenotypically. We also conducted various investigations to better understand its impact and assess potential control measures. We acquired fifty rainbow trout (approximately 70 g in weight) and transferred them to a laboratory aquarium. During the initial acclimation period, we observed mortality and examined affected fish for clinical signs. We isolated the bacterium from the spleen of infected rainbow trout using tryptone yeast extract salts agar supplemented with glucose, naming this FPRT1. Antibiotic susceptibility testing was carried out, and from the result, we selected enrofloxacin to administer to the trout orally to reduce mortality. To evaluate pathogenicity, we exposed the trout to FPRT1 at different water temperatures (8, 15, and 22 °C). Genomic analysis was conducted to identify the serotype and relatedness of FPRT1 to European strains. Affected fish displayed clinical signs, such as ulcerative lesions in the mandible, anemia with pale gills, exophthalmia, and increased mucus secretion. Internal symptoms included pale liver and enlarged spleen. FPRT1 was susceptible to erythromycin, enrofloxacin, florfenicol, oxytetracycline, and gentamicin, but resistant to oxolinic acid and sulfamethoxazole/trimethoprim. Oral administration of enrofloxacin resulted in a decrease in mortality from 28% to 6%. Pathogenicity tests revealed varying mortality rates due to FPRT1 at different temperatures. The highest rates were observed at 8 °C (ranging from 43% to 100%) for both intraperitoneal and intramuscular injections, and lower rates occurred at 22 °C (ranging from 0% to 30%), with intramuscular injections displaying higher susceptibility. Genomic analysis identified FPRT1 as serotype 2 and indicated its close genetic relationship with European strains based on the core genome and dispensable genome. The substantial genomic similarity between our strain and European strains suggests the possibility of bacterial spread through the importation of fertilized eggs from Europe. In conclusion, this study highlights the introduction of the previously undocumented pathogen (F. psychrophilum) into Korean rainbow trout populations. The detection of this pathogen and its pathogenicity assessment is not only important for understanding its impact on local aquaculture but also for establishing surveillance and control measures to prevent further transmission and outbreaks in the region. MDPI 2023-10-12 /pmc/articles/PMC10609541/ /pubmed/37894203 http://dx.doi.org/10.3390/microorganisms11102546 Text en © 2023 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Park, Jiyeon
Roh, HyeongJin
Lee, Yoonhang
Lee, Ju-Yeop
Kang, Hyo-Young
Seong, Min Ji
Kang, Yura
Heo, Young Ung
Kim, Bo Seong
Park, Chan-Il
Kim, Do-Hyung
Characterization and Pathogenicity of Flavobacterium psychrophilum Isolated from Rainbow Trout (Oncorhynchus mykiss) in Korea
title Characterization and Pathogenicity of Flavobacterium psychrophilum Isolated from Rainbow Trout (Oncorhynchus mykiss) in Korea
title_full Characterization and Pathogenicity of Flavobacterium psychrophilum Isolated from Rainbow Trout (Oncorhynchus mykiss) in Korea
title_fullStr Characterization and Pathogenicity of Flavobacterium psychrophilum Isolated from Rainbow Trout (Oncorhynchus mykiss) in Korea
title_full_unstemmed Characterization and Pathogenicity of Flavobacterium psychrophilum Isolated from Rainbow Trout (Oncorhynchus mykiss) in Korea
title_short Characterization and Pathogenicity of Flavobacterium psychrophilum Isolated from Rainbow Trout (Oncorhynchus mykiss) in Korea
title_sort characterization and pathogenicity of flavobacterium psychrophilum isolated from rainbow trout (oncorhynchus mykiss) in korea
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10609541/
https://www.ncbi.nlm.nih.gov/pubmed/37894203
http://dx.doi.org/10.3390/microorganisms11102546
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