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Affiliation |
Faculty of Agriculture Region of Marine Life Science |
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Title |
Associate Professor |
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External Link |
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Related SDGs |
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NISHIKI Issei
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Research Areas 【 display / non-display 】
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Life Science / Aquatic bioproduction science
Papers 【 display / non-display 】
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Isolation of Erythromycin (EM)-Resistant Enterococci Carrying Erm(B) From Aquaculture Water and Investigation of the Potential Conjugative Transfer of EM Resistance to Emerging Fish Pathogens, Lactococcus formosensis and Lactococcus garvieae Serotype III. Reviewed
Araki K, Iwao Y, Minami T, Nishiki I, Yoshida T
Journal of fish diseases e70110 2025.12
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吉田 照豊, 西木 一生
Microbiology and Biotechnology Letters 53 ( 3 ) 476 - 480 2025.9
Language：English Publishing type：Research paper (scientific journal) Publisher：Korean Society for Microbiology and Biotechnology
We present the complete genome of Weissella tructae strain TB02, accompanied by an in-depth genomic analysis of its key features. The genome is approximately 1,449,263 bp with a GC content of 40.6%, and encodes 1492 genes (1,393 coding sequences and 99 RNA genes). The genome shares over 99.9% identity with genomes of W. tructae strains from Weissellosis outbreaks in rainbow trout. Conversely, it exhibits 81.4% to 81.5% identity to the type strain Weissella ceti CECT 7719 and KACC 18534 from beaked whales. These findings enhance our understanding of its pathogenic role and its potential as a transboundary infectious agent globally.
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Araki Kaho, Itoda Takuma, Nishiki Issei, Yoshida Terutoyo
魚病研究 60 ( 3 ) 157 - 160 2025.9
Language：English Publishing type：Research paper (scientific journal) Publisher：日本魚病学会
<i>Lactococcus garvieae</i> serotype III infections have been found in striped jack <i>Pseudocaranx dentex</i> since 2021. In the absence of a vaccine against serotype III, erythromycin (EM) is used to treat this infection. In 2024, five EM-resistant <i>L.</i><i>garvieae</i> serotype III isolates were obtained from striped jack specimens. These isolates carried <i>erm</i>(B), an EM-resistance gene. The filter mating experiment confirmed that the EM-resistance trait was successfully transferred to <i>L.</i><i>formosensis</i> as the recipient. All biased sinusoidal field gel electrophoresis (BSFGE) patterns of these strains were similar to the BSFGE type A of the previous study and coincided with each other.
DOI： 10.3147/jsfp.60.157
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Araki Kaho, Nishiki Issei, Yoshida Terutoyo
魚病研究 59 ( 4 ) 119 - 126 2024.12
Language：English Publishing type：Research paper (scientific journal) Publisher：日本魚病学会
<i>Lactococcus garvieae</i> serotype III, a newly emerging pathogen that causes lactococcal infection, has been detected in fish farms since 2021. This pathogen has caused severe damage to the striped jack <i>Pseudocaranx dentex</i> and greater amberjack <i>Seriola dumerili</i>. This study collected strains from various fish species on farms between 2021 and 2023 and conducted an epidemiological and characterization study of <i>L. garvieae</i> serotype III using biochemical characterization tests, agglutinating titers against diagnostic antisera, biased sinusoidal field gel electrophoresis (BSFGE), and drug susceptibility tests. Capsule-like structures were found on the cell surfaces of <i>L. garvieae</i> serotype III strains, and strains showed similar characteristics except for the reaction of acidification ribose in biochemical characterization test using the API 20 STREP system. All strains were agglutinated with antiserum raised against <i>L. garvieae</i> serotype III and lower or non-agglutinated with antiserum raised against <i>L. garvieae</i> serotype I. BSFGE analysis identified three types of electrophoretic pattern: A, B, and C. BSFGE types A and B spread to fish farms in 2021, while type C found in 2022. All strains analyzed in this study were thought to be resistant to lincomycin but not to erythromycin.
DOI： 10.3147/jsfp.59.119
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Araki Kaho, Mouri Ayaka, Minami Takayuki, Nishiki Issei, Yoshida Terutoyo
Fish Pathology 59 ( 2 ) 63 - 70 2024.6
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Society of Fish Pathology
Pathogenic bacteria that cause lactococcal infections in marine aquaculture in Japan are currently classified into three types based on serotype and genetic characterization: <i>Lactococcus garvieae</i> type I, <i>L. formosensis</i> (formerly, <i>L. garvieae</i> type II), and <i>L. garvieae</i> type III. Although a slide agglutination test with rabbit antiserum is used to discriminate these three types, its accuracy is insufficient for clinical diagnosis owing to the existence of isolates that show agglutination with more than one diagnostic antiserum. Furthermore, a previously developed PCR assay was not able to distinguish <i>L. garvieae</i> type I from <i>L. garvieae</i> type III, a newly emerging pathogen. In this study, primers specific to each type were designed and applied in a newly developed multiplex PCR assay to discriminate these three types of lactococcal pathogens isolated from diseased fish. Amplification products with the expected sizes of 262, 1,007, and 500 bp could be obtained for <i>L. garvieae</i> type I, <i>L. formosensis</i>, and <i>L. garvieae</i> type III, respectively. Amplification products could not be obtained from isolates of <i>Lactococcus</i> spp. from non-marine fish species. These results show that the multiplex PCR assay can discriminate these three pathogens that cause lactococcal infections in fish farms.
DOI： 10.3147/jsfp.59.63
Presentations 【 display / non-display 】
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魚類養殖場におけるerm(B)保有エリスロマイシン(EM)耐性腸球菌の検出と魚類のレンサ球菌への耐性伝達
荒木香帆・岩尾 豊・南 隆之・西木一生・吉田照豊
令和7年度 日本魚病学会春季大会
Event date： 2025.3.17 - 2025.3.18
Language：Japanese Presentation type：Oral presentation (general)
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Lactococcus garvieae 血清型III型(III型レンサ球菌)のerm(B)を保有するエリスロマイシン(EM)耐性株の出現
荒木香帆・糸田拓馬・西木一生・吉田照豊
令和7年度 日本魚病学会春季大会
Event date： 2025.3.17 - 2025.3.18
Presentation type：Poster presentation
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Lactococcus garvieae III型の遺伝学的解析
西木一生・北村 大・吉田照豊
令和5年度日本魚病学会春季大会
Event date： 2023.3.14 - 2023.3.15
Presentation type：Poster presentation
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海産養殖魚におけるαレンサ球菌症原因細菌の同定方法の開発
毛利文香・西木一生・吉田照豊
令和4年度日本水産学会九州支部大会
Event date： 2023.1.7
Language：Japanese Presentation type：Oral presentation (general)
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海面養殖魚から分離した血清型不明の Lactococcus garvieae に関する研究 I
俵 佑誠・南 隆之・西木一生・吉田照豊
令和4年度日本魚病学会春季大会
Event date： 2022.3.5 - 2022.3.6
Presentation type：Oral presentation (general)
Grant-in-Aid for Scientific Research 【 display / non-display 】
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新型Lactococcus garvieae感染症の疫学調査およびワクチン開発に関する研究
Grant number：23K05396 2023.04 - 2026.03
独立行政法人日本学術振興会 科学研究費基金 基盤研究(C)
Authorship：Principal investigator
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ノカルジアの魚類マクロファージ内における生存戦略に関する研究
Grant number：18K05805 2018 - 2023
独立行政法人日本学術振興会 科学研究費基金 基盤研究(C)
Authorship：Coinvestigator(s)