Objective  To observe the periodontal status and salivary microbial diversity in patients with rheumatoid arthritis, and to analyze the relationship between the composition of oral microflora in patients with RA and the incidence of rheumatoid arthritis.

  Methods  24 patients who were diagnosed as rheumatoid arthritis were enrolled in the experimental group, and 20 healthy persons were enrolled in the control group. The periodontal index was recorded and non-irritating saliva was collected. DNA was extracted and high-throughput sequencing was performed.

  Results  There were no significant differences in periodontal indices between the RA group and the control group. After analysis of salivary microorganisms in RA patients and control group, there was no significant difference in salivary microbial diversity between RA patients and control group. At the phylum level, 13 phyla were found, including Firmicutes (30.2%), Proteobacteria (29.3%), Bacteroidetes (23.8%), Fusobacteria (7.3%), Actinobacteria (5.6%) as dominant bacteria. Bacteroidetes (P=0.04) and spirochoetes (P=0.01) were significantly higher in the RA group. A total of 144 genus were found, and 12 dominant genus were found. 11 genuses were found to have significant difference between the RA group and the control. At the genus level, Prevotella (P=0.03), Porphyromonas (P=0.005 7), Tannerella (P=0.001 9) and Treponema (P=0.010) were significantly higher in the RA group. Salivary microbial community similarity in the RA group was significantly higher than that in the control group.

  Conclusion  Compared with healthy people, RA patients had higher periodontal inflammation indices, but there was no statistical difference. The oral saliva of patients with rheumatoid arthritis has a unique microbial diversity structure. This result provides a new insight for understanding the pathogenesis of rheumatoid arthritis.