Human oral mucosa and saliva bacterial metagenome in RAU patients. human oral metagenome

Pyrosequencing data has been used to characterize the microbiota in the oral mucosa and saliva of RAU patients. Recurrent aphthous stomatitis (RAS) is a common oral mucosal disorder of unclear etiopathogenesis. Although recent studies of oral microbiota by high-throughput sequencing of 16S rRNA genes implied involvement of imbalanced oral microbiota in the etiopathogenesis of RAS, no specific bacterial species associated with RAS is known. The present study aimed to characterize the microbiota in the oral mucosa and saliva of RAS patients in comparison with control subjects. The bacterial communities of the oral mucosa and saliva from RAS patients with active lesions (RASAL, n=20 for mucosa and n=9 for saliva) and control subjects (n=19 for mucosa and n=8 for saliva) were analyzed by pyrosequencing of 16S rRNA genes. There were no significant differences in alpha diversity between controls and RASAL, but the mucosal microbiota of RASAL showed increased inter-subject variability. A comparison of the relative abundance of each taxon revealed dysbiosis of both the mucosal and salivary microbiota in RASAL patients. Particularly, decreased Streptococcus salivarius (in both the mucosa and saliva) and Veillonella dispar (in the mucosa) and increased Acinetobacter johnsonii (in the mucosa) were associated with RAS risk. A dysbiosis index developed using the abundance of A. johnsonii, S. salivarius, and V. dispar correctly predicted 82% of 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 and V. dispar. In conclusion, pyrosequencing analysis successfully characterized the oral microbiota of RAS patients in comparison with normal flora and revealed several taxa associated with RAS. This knowledge may provide a diagnostic tool and new targets for therapeutics of RAS.