研究者業績

倉田 修

クラタ オサム  (Osamu Kurata)

基本情報

所属
日本獣医生命科学大学 獣医学部 獣医学科 教授
学位
博士(水産学)

J-GLOBAL ID
200901072207237875
researchmap会員ID
1000192391

論文

 22
  • Goshi Kato, Hayato Nakajima, Kyuma Suzuki, Yuhei Kanzawa, Chihaya Nakayasu, Kosei Taguchi, Osamu Kurata, Motohiko Sano
    Frontiers in immunology 14 1101491-1101491 2023年  査読有り
    INTRODUCTION: Temporal elevation of water temperature positively affects immune activity and disease resistance in poikilothermic teleost fish. The ayu, Plecoglossus altivelis, an important fish species for Japanese freshwater fisheries, is usually produced under higher water temperatures than the natural conditions to facilitate rapid growth. However, it has been reported that rearing fish at higher water temperatures inhibits the development of the thymus, suggesting that resistance to infectious diseases is reduced in ayu reared at higher water temperatures. Here, we show that decreased resistance to bacterial cold-water disease and excessive inflammatory responses occurred in ayu reared at 22°C compared with those reared at lower temperatures. METHODS: Ayu larvae were reared at 12°C, 15°C and 22°C for 77 days and fed 3% of their body weight. Thymus index and condition factor was calculated after the fish rearing. Then, ayu reared at the different temperatures were challenged with Flavobacterium psychrophilum and the fish were sampled for histopathology and gene expression analyses. Further, the fish were vaccinated with formalin-killed F. psychrophilum and continuously reared at the three different water temperatures. Serum antibody titer was determined by ELISA and cumulative mortality in each group was recorded after the bacterial challenge. RESULTS: Ayu reared at 22°C showed a significantly lower thymus index and higher condition factor than those reared at lower temperatures. Infiltrated leukocytes and many melanin pigments were frequently observed in the adipose tissues and spleens of ayu reared at 22°C, respectively, but not in those reared at 12°C. The gene expression levels of inflammatory cytokines such as IL-1β, IL-8 and TNFα in the spleen were significantly higher in the 22°C group than in the 12°C group. The cumulative survival rate after challenge with Flavobacterium psychrophilum was 51.7%, 40.0% and 13.3% in the 12°C, 15°C and 22°C groups, respectively. The relative percent survival values of vaccinated fish reared at 15°C and 22°C groups were lower than those reared at 12°C. Moreover, the specific antibody titer of the vaccinated fish was the lowest in the 22°C group and the highest in the 12°C group. DISCUSSION: These results suggest that rearing the fish under high water temperature causes excessive inflammatory responses similar to metabolic inflammation in human obesity, resulting in a decrease of disease resistance. In addition, thymic involution induced by higher water temperature probably leads the poor response to vaccination. The present study provides insights into the physiological and immunological changes of fish under global warming.
  • 倉田 修, 羽地 雅, 川島 拓也, 八木澤 優, 齋藤 哲, 森 竜也
    魚病研究 57(3) 95-102 2022年9月15日  査読有り筆頭著者責任著者
    無機物の食品添加物で構成されるオキシリンクSPのサケ科卵のミズカビ病に対する防除効果を調べた。室内試験においてSaprolegnia属菌5種に対するオキシリンクSPの殺菌効果を検討した結果,30分間の薬浴では10,000倍以下の希釈で殺菌作用を示した。野外試験では,Saprolegnia属菌以外の菌類が発育したサクラマス卵を除き,ニジマスおよびイワナ卵での菌糸発育抑制効果を確認した。魚卵毒性については,生産上大きな被害はないが,ニジマス卵の発眼率および孵化率に影響を与えた。一方,イワナ卵およびサクラマス卵に対する影響は認められなかった。オキシリンクSPによる薬浴はサケ科卵を対象としたミズカビ病の防除に有用であるが,薬浴条件について検討する必要がある。
  • Osamu Kurata, Suyu Miyashita, Shinpei Wada
    Fish Pathology 56(4) 216-219 2021年12月15日  査読有り筆頭著者責任著者
  • Osamu Kurata, Suyu Miyashita, Shusei Toda, Shinpei Wada, Takamitsu Sakai
    Fish Pathology 55(4) 151-161 2021年1月15日  査読有り筆頭著者責任著者
  • Yozo Takada, Kosei Taguchi, Kyuma Suzuki, Akihiko Ashizawa, Koichi Kaji, Shun Watanabe, Shinpei Wada, Osamu Kurata
    Fish Pathology 55(2) 31-37 2020年6月  査読有り責任著者

MISC

 75
  • Takeshi Komine, Saralee Srivorakul, Mitsumi Yoshida, Yoshiaki Tanaka, Yuma Sugimoto, Mari Inohana, Hanako Fukano, Yoshihiko Hoshino, Osamu Kurata, Shinpei Wada
    Journal of fish diseases 46(5) 507-516 2023年5月  
    Mycobacterium marinum is a slow-growing, photochromogenic nontuberculous mycobacterium, which can cause mycobacteriosis in various animals, including humans. Several cases of fish mycobacteriosis have been reported to date. Mycobacterium marinum has also been isolated from aquatic environmental sources such as water, sand, biofilms, and plants in the natural environments. Hence, we hypothesized that a wide variety of sources could be involved in the transmission of M. marinum. In this study, we tested this hypothesis by isolating M. marinum from various sources such as fish, invertebrates, seagrass, periphytons, biofilms, sand, and/or water in two aquaria in Japan and conducting a phylogenetic analysis based on single-nucleotide polymorphisms (SNPs) using whole-genome sequences of the isolated strains. The analysis revealed that the strains from animal and environmental sources belonged to the same clusters. This molecular-based study epidemiologically confirmed that various sources, including fish, invertebrates, and environmental sources, could be involved in transmission of M. marinum in a closed-rearing environment. This is the first report where M. marinum was isolated from different sources, and various transmission routes were confirmed in actual cases, which provided essential information to improve the epidemiology of M. marinum.
  • Takeshi Komine, Yuko Matsuoka, Mari Inohana, Osamu Kurata, Shinpei Wada
    Microbiology resource announcements 12(3) e0113522 2023年3月16日  
    Mycobacterium chelonae is a nontuberculous mycobacterium that causes infections in various animals, including humans. In this study, we report the draft genome sequence of M. chelonae subsp. bovis strain NJB1701, which was isolated from a Baikal seal (Pusa sibirica) in captivity in Japan.
  • Takeshi Komine, Hyogo Ihara, Mari Inohana, Jennifer Caroline Kwok, Akane Shimizu, Tsumugi Terasawa, Ayaka Miyazaki, Saralee Srivorakul, Hajime Iwao, Sachiko Harada, Mitsunori Yoshida, Yoshihiko Hoshino, Osamu Kurata, Hanako Fukano, Shinpei Wada
    Frontiers in veterinary science 10 1248288-1248288 2023年  
    INTRODUCTION: Mycobacterium montefiorense is one of the causes of non-tuberculous mycobacterial infections in moray eels and salamanders. Although M. montefiorense infection could be a threat to salamanders, little information is available regarding this pathogen and associated infection. This study aimed to provide fundamental information regarding M. montefiorense and its infection in salamanders. METHODS: Nine M. montefiorense strains isolated from three species of salamanders, namely, Japanese black salamander (Hynobius nigrescens), Hakuba salamander (H. hidamontanus), and Tohoku hynobiid salamander (H. lichenatus), between 2010 and 2018, were characterized based on phenotypic and genetic examination. We also pathologically observed salamanders infected with the M. montefiorense strains, including Hakuba salamanders and Tohoku hynobiid salamanders. RESULTS: The microbiological and chemical characteristics of the M. montefiorense salamander and an eel strain (reference strain) matched. Susceptibility testing for antimicrobials suggested that clarithromycin may be effective. Regarding disinfectants, phtharal, peracetic acid, glutaral, sodium hypochlorite, and benzalkonium chloride may be effective. Phylogenetic analyses revealed that the strains isolated from salamanders in 2014 and 2018 were genetically closely related, which could indicate an outbreak. The main gross findings in infected salamanders include skin ulcerative lesions or nodules in the enlarged liver. Microscopically, multifocal to coalescent granulomatous lesions composed of massive macrophages containing numerous acid-fast bacilli were prominently observed in the liver. CONCLUSION: This study contributes to our understanding of the genetic diversity and phenotypic characteristics of M. montefiorense, as well as the pathology of the infection.
  • Mari Inohana, Takeshi Komine, Yoshiaki Tanaka, Osamu Kurata, Shinpei Wada
    Journal of fish diseases 46(1) 47-59 2023年1月  
    Mycobacterium marinum is a prevalent nontuberculous mycobacterium (NTM)-infecting teleosts. Conversely, little is known about mycobacteriosis in elasmobranchs, and M. marinum infection has never been reported from the subclass. This study investigated the histopathological characteristics and localization of this mycobacterium through molecular analysis of two captive sharks, a scalloped hammerhead Sphyrna lewini and a Japanese bullhead shark Heterodontus japonicus, exhibited in the same aquarium tank. We detected genital mycobacteriosis caused by M. marinum infection using molecular analyses, including polymerase chain reaction (PCR) and DNA sequencing targeting the 60 kDa heat-shock protein gene (hsp65), and peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH) targeting the 16S rRNA gene. Both sharks showed granulomas in connective tissues of the gonads without central necrosis or surrounding fibrous capsules, which is unlike the typical mycobacterial granulomas seen in teleosts. This study reveals that elasmobranchs can be aquatic hosts of M. marinum. Because M. marinum is a representative waterborne NTM and a potential zoonotic agent, cautious and intensive research is needed to overcome a lack of data on the relationship between NTM and the aquatic environment in association with this subclass of Chondrichthyes.
  • Takeshi Komine, Hyogo Ihara, Kentaro Ono, Mitsumi Yoshida, Yuma Sugimoto, Mari Inohana, Hanako Fukano, Osamu Kurata, Shinpei Wada
    The Journal of veterinary medical science 84(12) 1617-1620 2022年11月18日  
    In 2019, several aquarium-reared fish died at a sea life park in Japan. Necropsy revealed micronodules on the spleen in the dotted gizzard shad (Konosirus punctatus). Seven of 16 fish exhibited microscopic multifocal granulomas associated with acid-fast bacilli in the spleen, kidney, liver, alimentary tract, mesentery, gills, and/or heart. Bacterial cultures yielded isolates from the dotted gizzard shad and a Japanese sardine (Sardinops melanostictus). Microbiological and molecular biological examinations revealed the isolates as Mycobacterium pseudoshottsii. To our knowledge, this is the first isolation of M. pseudoshottsii from aquarium-reared fish.

書籍等出版物

 5

講演・口頭発表等

 108

担当経験のある科目(授業)

 3

共同研究・競争的資金等の研究課題

 16

産業財産権

 3