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Toru Takeshita Last modified date:2023.06.09

Professor / Section of Oral Health, Growth and Development
Department of Dental Science
Faculty of Dental Science

Graduate School
Undergraduate School
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Academic Degree
Country of degree conferring institution (Overseas)
Field of Specialization
Preventive Dentistry
Total Priod of education and research career in the foreign country
Outline Activities
Research activities
Study of the influence of oral microflora on oral or systemic health

Educational activities
1) Lecutre on and practice in oral microbiology, preventive dentistry, oral health science, and social dentistry to udnergraduate students
2) Clinical education on preventive dentistry to postgraduate students
3) Research instruction on preventive dentistry to postgraduate students

Social acitivties
1) Support of community dental health activity in health center and Hisayama town
Research Interests
  • Study of the influence of oral mirobiota on oral or systemic health
    keyword : Oral microbiota, T-RFLP, 16S rRNA gene
Academic Activities
1. Toru Takeshita, Yoshihisa Yamashita, Evaluation of salivary microbiota from an ecological perspectives, J Oral Bioscience, 2012.10.
1. Saori Oku, Toru Takeshita, Toshiko Futatsuki, Shinya Kageyama, Mikari Asakawa, Yasuo Mori, Toshihiro Miyamoto, Jun Hata, Toshiharu Ninomiya, Haruhiko Kashiwazaki, Yoshihisa Yamashita, Disrupted tongue microbiota and detection of nonindigenous bacteria on the day of allogeneic hematopoietic stem cell transplantation, PLoS pathogens, 10.1371/journal.ppat.1008348, 16, 3, 2020.01, Disruption of the intestinal microbiota caused by intensive chemotherapy, irradiation and antibiotics can result in development of severe gut graft-versus-host disease and infectious complications, leading to poorer outcomes among allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Although the oral cavity is also densely colonized by indigenous microorganisms, the bacterial composition in allo-HSCT recipients remains unclear. We determined the tongue microbiota composition of 45 patients with hematological disorders on the day of transplantation and compared them to 164 community-dwelling adults. The V1-V2 regions of the 16S rRNA gene sequences demonstrated that the allo-HSCT recipients had less diverse and distinct microbiota from that of community-dwelling adults. The full-length 16S rRNA gene sequences identified 146 bacterial taxa in the microbiota of allo-HSCT recipients, of which 34 bacterial taxa did not correspond to bacteria primarily inhabiting the oral cavity deposited in the expanded Human Oral Microbiome Database. Notably, the detection of Staphylococcus haemolyticus and/or Ralstonia pickettii was significantly associated with a higher risk of mortality during the follow-up period. These results demonstrate that the oral cavity of allo-HSCT recipients is colonized by a disrupted microbiota on the day of transplantation and suggest that detection of specific nonindigenous taxa could be a predictor of transplant outcome..
2. Yukari Ihara, Toru Takeshita, Shinya Kageyama, Rie Matsumi, Mikari Asakawa, Yukie Shibata, Yuki Sugiura, Kunio Ishikawa, Ichiro Takahashi, Yoshihisa Yamashita, Identification of initial colonizing bacteria in dental plaques from young adults using full-length 16S rRNA gene sequencing, mSystems, 10.1128/mSystems.00360-19, 4, 5, 2019.01, Development of dental plaque begins with the adhesion of salivary bacteria to the acquired pellicle covering the tooth surface. In this study, we collected in vivo dental plaque formed on hydroxyapatite disks for 6 h from 74 young adults and identified initial colonizing taxa based on full-length 16S rRNA gene sequences. A long-read, single-molecule sequencer, PacBio Sequel, provided 100,109 high-quality full-length 16S rRNA gene sequence reads from the early plaque microbiota, which were assigned to 90 oral bacterial taxa. The microbiota obtained from every individual mostly comprised the 21 predominant taxa with the maximum relative abundance of over 10% (95.8 6.2%, mean SD), which included Streptococcus species as well as nonstreptococcal species. A hierarchical cluster analysis of their relative abundance distribution suggested three major patterns of microbiota compositions: a Streptococcus mitis/Streptococcus sp. HMT-423-dominant profile, a Neisseria sicca/Neisseria flava/Neisseria mucosadominant profile, and a complex profile with high diversity. No notable variations in the community structures were associated with the dental caries status, although the total bacterial amounts were larger in the subjects with a high number of caries-experienced teeth (8) than in those with no or a low number of caries-experienced teeth. Our results revealed the bacterial taxa primarily involved in early plaque formation on hydroxyapatite disks in young adults. IMPORTANCE Selective attachment of salivary bacteria to the tooth surface is an initial and repetitive phase in dental plaque development. We employed full-length 16S rRNA gene sequence analysis with a high taxonomic resolution using a third-generation sequencer, PacBio Sequel, to determine the bacterial composition during early plaque formation in 74 young adults accurately and in detail. The results revealed 21 bacterial taxa primarily involved in early plaque formation on hydroxyapatite disks in young adults, which include several streptococcal species as well as nonstreptococcal species, such as Neisseria sicca/N. flava/N. mucosa and Rothia dentocariosa. Given that no notable variations in the microbiota composition were associated with the dental caries status, the maturation process, rather than the specific bacterial species that are the initial colonizers, is likely to play an important role in the development of dysbiotic microbiota associated with dental caries..
3. Mikari Asakawa, Toru Takeshita, Michiko Furuta, Shinya Kageyama, Kenji Takeuchi, Jun Hata, Toshiharu Ninomiya, Yoshihisa Yamashita, Tongue Microbiota and Oral Health Status in Community-Dwelling Elderly Adults, mSphere, 10.1128/mSphere.00332-18, 3, 4, 2018.08, Tongue microbiota are a dominant source of oral microbial populations that are ingested with saliva, and therefore careful attention is required for the maintenance of health of elderly adults, who are susceptible to aspiration of oral contents. This study aimed to investigate the variation in tongue microbiota among community-dwelling elderly adults. Following a dental examination, tongue coating was collected from a 15-mm-diameter circular area at the center of the tongue dorsum of 506 elderly adults aged 70 to 80 years inhabiting the town of Hisayama, Japan. The microbial composition and density were determined by a 16S rRNA gene sequencing approach using a next-generation sequencer and quantitative PCR analysis, respectively. Co-occurrence network analysis identified two cohabiting groups of predominant commensals, one of which was primarily composed of Prevotella histicola, Veillonella atypica, Streptococcus salivarius, and Streptococcus parasanguinis; these organisms have been previously associated with an increased risk of mortality due to pneumonia in the frail elderly. This bacterial group was more predominant in the elderly with fewer teeth, a higher plaque index, and more dental caries experience, whereas the total bacterial density was independent of these traits. A higher density of fungi was also observed in the elderly with these traits, as well as in individuals who wore dentures. These results suggest that elderly adults with poorer oral health swallow a more dysbiotic microbiota formed on the tongue.IMPORTANCE Aspiration of oral contents can lead to pneumonia, which is a major cause of death among elderly adults susceptible to swallowing impairments. Tongue microbiota are a dominant source of oral microbial populations that are ingested with saliva. This large-scale population-based study revealed variations in the tongue microbiota among community-dwelling elderly adults. The total bacterial density was independent of the conditions of teeth surrounding the tongue, whereas the microbiota composition, especially the relative abundances of predominant commensals, showed an association with tooth conditions. Our results demonstrate that the elderly with fewer teeth, poorer dental hygiene, and more dental caries experience constantly ingest more dysbiotic microbiota, which could be harmful for their respiratory health..
4. Shinya Kageyama, Toru Takeshita, Michiko Furuta, Mikiko Tomioka, Mikari Asakawa, Shino Suma, Kenji Takeuchi, Yukie Shibata, Yasuyuki Iwasa, Yoshihisa Yamashita, Relationships of variations in the tongue microbiota and pneumonia mortality in nursing home residents, Journals of Gerontology - Series A Biological Sciences and Medical Sciences, 10.1093/gerona/glx205, 73, 8, 1097-1102, 2018.01, Background: Aspiration of oral debris, containing dense oral bacteria, is a major cause of pneumonia in elderly adults. This study investigated the relationship between tongue microbiota composition and incidence of pneumonia-related deaths, in nursing home residents. Methods: The subjects were assessed for health conditions, including their tongue microbiota, at baseline. We determined tongue microbiota profiles by 16S ribosomal RNA gene sequencing and clustering approach. All subjects (n = 173) were followed prospectively for a median of 19 months to assess the incidence of all-cause death, including pneumonia-related death. We evaluated risk estimates of microbiota effects on death using multivariate Cox proportional hazards regression analysis. Results: Tongue microbiota were classified into two community types: type I was dominated by Prevotella and Veillonella species, while type II was dominated by Neisseria and Fusobacterium species. The subjects with type I microbiota exhibited a significantly greater risk of all-cause death (adjusted hazard ratio [aHR] = 3.79, 95% confidence interval [CI] = 1.38-10.39) and pneumonia-related death (aHR = 13.88, 95% CI = 1.64-117.21), than those with type II microbiota. There was no significant association between microbiota type and other-cause death. Conclusions: The tongue microbiota type was significantly associated with an increased mortality risk from pneumonia in nursing home residents..
5. Toru Takeshita, Shinya Kageyama, Michiko Furuta, Hidenori Tsuboi, Kenji Takeuchi, Yukie Shibata, Yoshihiro Shimazaki, Sumio Akifusa, Toshiharu Ninomiya, Yutaka Kiyohara, Yoshihisa Yamashita, Bacterial diversity in saliva and oral health-related conditions
The Hisayama Study, Scientific reports, 10.1038/srep22164, 6, 2016.02, This population-based study determined the salivary microbiota composition of 2,343 adult residents of Hisayama town, Japan, using 16S rRNA gene next-generation high-throughput sequencing. Of 550 identified species-level operational taxonomic units (OTUs), 72 were common, in ≥75% of all individuals, as well as in ≥75% of the individuals in the lowest quintile of phylogenetic diversity (PD). These "core" OTUs constituted 90.9 ± 6.1% of each microbiome. The relative abundance profiles of 22 of the core OTUs with mean relative abundances ≥1% were stratified into community type I and community type II by partitioning around medoids clustering. Multiple regression analysis revealed that a lower PD was associated with better conditions for oral health, including a lower plaque index, absence of decayed teeth, less gingival bleeding, shallower periodontal pockets and not smoking, and was also associated with tooth loss. By contrast, multiple Poisson regression analysis demonstrated that community type II, as characterized by a higher ratio of the nine dominant core OTUs, including Neisseria flavescens, was implicated in younger age, lower body mass index, fewer teeth with caries experience, and not smoking. Our large-scale data analyses reveal variation in the salivary microbiome among Japanese adults and oral health-related conditions associated with the salivary microbiome..
6. Toru Takeshita, Yoshio Nakano, Takashi Kumagai, Masaki Yasui, Noriaki Kamio, Yukie Shibata, Susumu Shiota, Yoshihisa Yamashita, The ecological proportion of indigenous bacterial populations in saliva is correlated with oral health status, ISME Journal, 10.1038/ismej.2008.91, 3, 1, 65-78, 2009.01, To obtain deeper insights into the etiology of oral disease, an understanding of the composition of the surrounding bacterial environments that lead to health or disease is required, which is attracting increasing attention. In this study, the bacterial compositions in the saliva of 200 subjects aged 15-40 years were depicted as peak patterns by terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA genes. The subjects were classified into three clusters by partitioning around medoids clustering based on their T-RFLP profiles, and the clinical oral health parameters of the clusters were compared. The clustering of the T-RFLP profiles in this study was mainly based on differences in the abundance distribution of the dominant terminal restriction fragments (TRFs) detected in most of the subjects. Predicted from the sizes of the TRFs, the characteristically more predominant members of each were Prevotella and Veillonella species in cluster I; Streptococcus species in cluster II and Neisseria, Haemophilus or Aggregatibacter species and Porphyromonas species in cluster III. The parameters associated with periodontal disease were significantly different among the clusters. Clusters I and II had a higher percentage of sites of periodontal pockets greater than 4 mm than cluster III, and cluster I contained sites exhibiting bleeding on probing more often than cluster II or III; no significant differences were observed in other parameters. These results suggest that the abundance distribution of commensal bacteria in saliva is correlated with periodontal health, and might be involved in the susceptibility of an individual to periodontal disease..
Educational Activities
1) Lecutre on and practice in oral microbiology, preventive dentistry, oral health science, and social dentistry to undergraduate students
2) Clinical education on preventive dentistry to postgraduate students
3) Research instruction on preventive dentistry to postgraduate students
Professional and Outreach Activities
1) Halitosis clinic in Kyushu University Hospital
2) Support of community dental health activity in health center and Hisayama town.