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• Pathogenesis of Vibrio cholerae

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• Significant removal of bacterial biofilm induced by multiple-Short ranges of electric interventions*

  Taira, H; Yaga, M; Nakasone, S; Nishida, K; Yamashiro, T

  JOURNAL OF ORTHOPAEDIC SCIENCE ( Journal of Orthopaedic Science )  29 ( 1 ) 341 - 348   2024.01 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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• Significant removal of bacterial biofilm induced by multiple short ranges of electric interventions

  Hiroyuki Taira, Minoru Yaga, Satoshi Nakasone, Kotaro Nishida, Tetsu Yamashiro

  Journal of Orthopaedic Science     2023.01 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

• Fermentation products of the fungus Monascus spp. impairs the physiological activities of toxin-producing Vibrio cholerae

  Jun Xu, Rino Arakaki, Shinjiro Tachibana, Tetsu Yamashiro

  Microbiological Research ( Elsevier BV )  258   126995   2022.05 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Monascus spp. are filamentous fungi used in fermented foods. They are also natural colorants and food preservatives. Certain metabolites of Monascus spp. lower cholesterol and have other health-promoting effects in humans. In the present study, we demonstrated that the fermentation products of Monascus spp. inhibited ATP synthesis and motility in toxigenic Vibrio cholerae. Single-cell tracking and rotation assays on single flagella showed that Monascus fermentation extract (MFE) significantly impaired V. cholerae swimming by disrupting flagellar rotation. A membrane potential-sensitive carbocyanine dye revealed that MFE depolarized the V. cholerae cell membrane which, in turn, lowered the membrane potential and, by extension, restricted ATP synthesis and flagellar rotation. MFE also severely hindered the motility of other pathogenic bacteria such as V. parahaemolyticus, Pseudomonas aeruginosa, Salmonella enterica Typhimurium, and Leptospira interrogans. The foregoing findings indicate that Monascus fermentation extract could potentially preventing infection caused by multiple pathogenic bacteria as the conventional prophylaxes and slow their progression and lower mortality and morbidity.

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• Fermentation products of the fungus Monascus spp. impairs the physiological activities of toxin-producing Vibrio cholerae.

  Xu J, Arakaki R, Tachibana S, Yamashiro T

  Microbiological research ( Microbiological Research )  258   126995 - 126995   2022.05 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

  　View Summary

  Monascus spp. are filamentous fungi used in fermented foods. They are also natural colorants and food preservatives. Certain metabolites of Monascus spp. lower cholesterol and have other health-promoting effects in humans. In the present study, we demonstrated that the fermentation products of Monascus spp. inhibited ATP synthesis and motility in toxigenic Vibrio cholerae. Single-cell tracking and rotation assays on single flagella showed that Monascus fermentation extract (MFE) significantly impaired V. cholerae swimming by disrupting flagellar rotation. A membrane potential-sensitive carbocyanine dye revealed that MFE depolarized the V. cholerae cell membrane which, in turn, lowered the membrane potential and, by extension, restricted ATP synthesis and flagellar rotation. MFE also severely hindered the motility of other pathogenic bacteria such as V. parahaemolyticus, Pseudomonas aeruginosa, Salmonella enterica Typhimurium, and Leptospira interrogans. The foregoing findings indicate that Monascus fermentation extract could potentially preventing infection caused by multiple pathogenic bacteria as the conventional prophylaxes and slow their progression and lower mortality and morbidity.

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• Analysis of human clinical and environmental Leptospira to elucidate the eco-epidemiology of leptospirosis in Yaeyama, subtropical Japan

  Yukuto Sato , Idam Hermawan , Tetsuya Kakita , Sho Okano , Hideyuki Imai , Hiroto Nagai , Ryosuke Kimura , Tetsu Yamashiro , Tadashi Kajita , Claudia Toma

  PLOS Neglected Tropical Diseases ( Public Library of Science (PLoS) )  16 ( 3 ) e0010234 - e0010234   2022.03 [ Peer Review Accepted ]

  Type of publication: Research paper (scientific journal)

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  Background Leptospirosis, a zoonosis caused by species in the spirochete genus Leptospira, is endemic to the Yaeyama region in Okinawa, subtropical Japan. Species of the P1 subclade “virulent” group, within the genus Leptospira, are the main etiological agents of leptospirosis in Okinawa. However, their environmental persistence is poorly understood. This study used a combination of bacterial isolation and environmental DNA (eDNA) metabarcoding methods to understand the eco-epidemiology of leptospirosis in this endemic region. Findings Polymerase chain reaction (PCR) characterized twelve human clinical L. interrogans isolates belonging to the P1 subclade “virulent” subgroup and 11 environmental soil isolates of the P1subclade “low virulent” subgroup (genetically related to L. kmetyi, n = 1; L. alstonii, n = 4; L. barantonii, n = 6) from the Yaeyama region targeting four virulence-related genes (lipL32, ligA, ligB and lpxD1). Clinical isolates were PCR positive for at least three targeted genes, while all environmental isolates were positive only for lipL32. Analysis of infected renal epithelial cells with selected clinical and environmental strains, revealed the disassembly of cell-cell junctions for the Hebdomadis clinical strain serogroup. Comparison of leptospiral eDNA during winter and summer identified operational taxonomic units corresponding to the species isolated from soil samples (L. kmetyi and L. barantonii) and additional P2 subclade species (L. licerasiae, L. wolffii-related, among others) that were not detected by soil cultivation. Total Leptospira read counts were higher in summer than in winter and the analysis of leptospiral/animal eDNA relationship suggested Rattus spp. as a potential reservoir animal. Conclusion Our study demonstrated high environmental Leptospira diversity in the Yaeyama region, particularly during summer, when most of the leptospirosis cases are reported. In addition, several Leptospira species with pathogenic potential were identified that have not yet been reported in Yaeyama; however, the environmental persistence of P1 subclade species previously isolated from human clinical cases in this region was absent, suggesting the need of further methodology development and surveillance.

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• 北部ベトナム農村地域における下痢原性腸管寄生原虫Cryptosporidium spp.の検出と疫学的背景について

  櫻井 優輝, 岩下 華子, 山城 哲

  琉球医学会誌 ( 琉球医学会 )  37 ( 1-4 ) 121 - 121   2018.12

   

• Vibrio cholerae O1 El Tor from southern Vietnam in 2010 was molecularly distinct from that present from 1999 to 2004

  V. H. Nguyen, H. T. Pham, T. T. Diep, C. D.H. Phan, T. Q. Nguyen, N. T.N. Nguyen, T. C. Ngo, T. V. Nguyen, Q. K. Do, H. C. Phan, B. M. Nguyen, M. Ehara, M. Ohnishi, T. Yamashiro, L. T.P. Nguyen, H. Izumiya

  Epidemiology and Infection ( Cambridge University Press )  144 ( 6 ) 1241 - 1247   2016.04

   

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• Construction of Human Neutralizing Antibody against Rabies

  2001

  　

  　

   

• Seroprevalence of Dengue Virus Specific IgG among Residents in Santo Domingo, Dominican Republic

  1900.01

  　

  　

   

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Academic Awards 【 display / non-display 】

• Award of Japanese Society of Tropical Medicine

  1900.01.01   Japanese Society of Tropical Medicine   Molecular Epidemiological Analysis on Vibrio cholerae in Asia

  Winner: Tetsu Yamashiro

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• Grant-in-Aid for Scientific Research(C)

  Project Year: 2022.04  -  2025.03 

  Direct: 3,100,000 (YEN)  Overheads: 4,030,000 (YEN)  Total: 930,000 (YEN)

• Grant-in-Aid for Scientific Research(A)

  Project Year: 2016.04  -  2020.03 

  Direct: 31,700,000 (YEN)  Overheads: 9,510,000 (YEN)  Total: 41,210,000 (YEN)

• Diarrhea in Vietnam

  Grant-in-Aid for Scientific Research(A)

  Project Year: 2016.04  -  2020.03 

  Investigator(s): Yamashiro Tetsu 

  Direct: 31,700,000 (YEN)  Overheads: 41,210,000 (YEN)  Total: 9,510,000 (YEN)

  　View Summary

  We have analyzed 2120 diarrheal stool samples collected in Nam Dinh Province in northern Vietnam and compared the detection rates and profiles of diarrheagenic microorganisms with those of the 471 non-diarrheal stool samples. The detection rate of diarrheagenic microorganisms was 13.1% for diarrheal stool samples and 8.4% for non-diarrheal stool samples, showing a significant difference. The incidence of diarrheal disease seemed to be higher among users of the public water supply facilities, and users of pit-type toilets. In the study, Salmonella spp., Aeromonas spp., Campylobacter., Shigella spp., and Vibrio spp. were less frequently detected, while Entamoeba hitolytica, Giardia spp., and Cryptosporidium spp. were commonly detected in a wide range of age groups. Analysis of stool samples collected from livestock animals indicated Giardia spp. and Cryptosporidium spp. may be transmitted from livestock animals to humans.

• A community based study of diarrheal diseases in agricultural village in northern Vietnam

  Grant-in-Aid for Scientific Research(B)

  Project Year: 2013.04  -  2016.03 

  Investigator(s): YAMASHIRO Tetsu, HASHIZUME Masahiro 

  Direct: 14,000,000 (YEN)  Overheads: 18,200,000 (YEN)  Total: 4,200,000 (YEN)

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  A prospective community based diarrheal study was conducted in a typical agricultural area in Nam Dinh province in northern Vietnam in the study period. A 300 out of approx. 2,100 households were randomly chosen, and stool samples and epidemiological data were collected in order to estimate 1) distributions of etiological agents of; and 2) possible risk factors for diarrhea. Approximately 1,200 diarrheal sapmles were collected and analyzed in the study, and rotavirus, adenovirus, any categories of diarrheagenic Escherichia coli, Clostridium difficicile, and Entoamoeba histolytica were estimated as significant etiologies of diarrhea including mild to moderate cases in the community. Approximately 20% of the all households raised livestock animals including cows, pigs, and poultry, and of those, cow raising was estimated to be a risk factor for Giardia infections, one of the intestinal protozoa to cause diarrhea, in Hien Khanh commune.