title: Mucosal and salivary microbiota associated with recurrent aphthous stomatitis.
abstract: BACKGROUND
  Recurrent aphthous stomatitis (RAS) is a common oral mucosal disorder of unclear etiopathogenesis. Although recent studies of the oral microbiota by high-throughput sequencing of 16S rRNA genes have suggested that imbalances in the oral microbiota may contribute to the etiopathogenesis of RAS, no specific bacterial species associated with RAS have been identified. The present study aimed to characterize the microbiota in the oral mucosa and saliva of RAS patients in comparison with control subjects at the species level.
  
  
  RESULTS
  The bacterial communities of the oral mucosa and saliva from RAS patients with active lesions (RAS, n = 18 for mucosa and n = 8 for saliva) and control subjects (n = 18 for mucosa and n = 7 for saliva) were analyzed by pyrosequencing of the 16S rRNA genes. There were no significant differences in the alpha diversity between the controls and the RAS, but the mucosal microbiota of the RAS patients showed increased inter-subject variability. A comparison of the relative abundance of each taxon revealed decreases in the members of healthy core microbiota but increases of rare species in the mucosal and salivary microbiota of RAS patients. Particularly, decreased Streptococcus salivarius and increased Acinetobacter johnsonii in the mucosa were associated with RAS risk. A dysbiosis index, which was developed using the relative abundance of A. johnsonii and S. salivarius and the regression coefficients, correctly predicted 83 % of the total cases for the absence or presence of RAS. Interestingly, A. johnsonii substantially inhibited the proliferation of gingival epithelial cells and showed greater cytotoxicity against the gingival epithelial cells than S. salivarius.
  
  
  CONCLUSIONS
  RAS is associated with dysbiosis of the mucosal and salivary microbiota, and two species associated with RAS have been identified. This knowledge may provide a diagnostic tool and new targets for therapeutics for RAS.
authors.affiliation: Department of Oral Microbiology and Immunology, School of Dentistry and Dental Research Institute, Seoul National University, 101 Daehak-ro, Seoul, Jongno-gu, 110-744, Republic of Korea.
authors.forename: Yun-Ji
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Department of Oral Microbiology and Immunology, School of Dentistry and Dental Research Institute, Seoul National University, 101 Daehak-ro, Seoul, Jongno-gu, 110-744, Republic of Korea.
authors.forename: Yun Sik
authors.initials: YS
authors.lastname: Choi
authors.affiliation: Department of Oral Microbiology and Immunology, School of Dentistry and Dental Research Institute, Seoul National University, 101 Daehak-ro, Seoul, Jongno-gu, 110-744, Republic of Korea.
authors.forename: Keum Jin
authors.initials: KJ
authors.lastname: Baek
authors.affiliation: School of Biological Sciences, Seoul National University, Seoul, Republic of Korea.
authors.forename: Seok-Hwan
authors.initials: SH
authors.lastname: Yoon
authors.affiliation: Department of Oral Medicine and Oral Diagnosis, School of Dentistry and Dental Research Institute, Seoul National University, 101 Daehak-ro, Seoul, Jongno-gu, 110-744, Republic of Korea. dentopark@snu.ac.kr.
authors.forename: Hee Kyung
authors.initials: HK
authors.lastname: Park
authors.affiliation: Department of Oral Microbiology and Immunology, School of Dentistry and Dental Research Institute, Seoul National University, 101 Daehak-ro, Seoul, Jongno-gu, 110-744, Republic of Korea. youngnim@snu.ac.kr.
authors.forename: Youngnim
authors.initials: Y
authors.lastname: Choi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D064806:Dysbiosis / Q000382:microbiology; D005260:Female; D006801:Humans; D008297:Male; D064307:Microbiota; D008875:Middle Aged; D009061:Mouth Mucosa / Q000382:microbiology*; D012463:Saliva / Q000382:microbiology*; D013281:Stomatitis, Aphthous / Q000382:microbiology*; D055815:Young Adult
keywords: Oral microbiota; Pyrosequencing; Recurrent aphthous stomatitis