Porphyromonas gingivalis amount in the tongue biofilm is associated with erosive arthritis in systemic lupus erythematosus

Background Several data have demonstrated the occurrence of erosive arthritis in Systemic Lupus Erythematosus (SLE) patients. However, a few studies have focused on the pathogenic mechanisms involved in this feature. The implication of oral pathogens has been proved in Rheumatoid Arthritis: in particular, Porphyromonas gingivalis (Pg), by inducing citrullination, could trigger autoimmune response. Here, we evaluated amount of Pg on the tongue in a cohort of SLE patients with arthritis, focusing on the association with the erosive phenotype. Methods SLE patients with arthritis were enrolled. DAS28 was applied to assess activity. Erosive damage was evaluated by ultrasound at level of MCP (metacarpophalangeal) and PIP (proximal interphalangeals) joints. All subjects underwent a tongue cytologic swab in order to quantify the amount of Pg (real-time PCR). The bacterium expression was obtained from the ratio between the patient's DNA amount and that obtained from healthy subjects. Results 33 patients were enrolled (M/F 3/30; median age 47 years, IQR 17; median disease duration 216 months, IQR 180): 12 of them (36.4%) showed erosive damage, significantly associated with ACPA positivity (p = 0.03) and higher values of DAS28 (p = 0.01). A mean ratio of 19.7 +/- 31.1 was found for Pg amount. Therefore, we used Pg mean values as threshold, identifying two groups of patients, namely, ( high )Pg and ( low )Pg. Erosive damage was significantly more frequent in ( high )Pg patients in comparison with ( low )Pg (60.0% vs 26.0%, p = 0.001). Furthermore, ( high )Pg patients showed higher prevalence of skin manifestations, serositis, and neurological involvement (p = 0.005, p = 0.03, p = 0.0001, respectively). Conclusion The possible contribution of oral microbiota in SLE erosive arthritis was here evaluated for the first time, finding a significant association between erosive damage and higher expression of Pg at tongue level.

Automated summary

This study evaluated the possible involvement of oral microbiota in SLE erosive arthritis for the first time, finding a significant association between erosive damage and higher expression of Pg on the tongue. High levels of Pg were associated with more frequent erosive damage and other systemic manifestations in SLE patients.