Mycoplasma fermentans in rheumatoid arthritis and other inflammatory arthritides

Objective. To evaluate the association between infection with Mycoplasma fermentans (Mf) and rheumatoid arthritis (RA) and other inflammatory arthritides. Methods. Screening of synovial fluid samples (SF) for Mf was done by culture and by polymerase chain reaction (PCR) in 38 and 34 RA patients, respectively, 8 undifferentiated arthritis (UDA), 9 reactive arthritis (ReA), and in 40 other arthritides. The prevalence of antibodies to Mf in these SF was determined by both ELISA and immunoblotting (IB). Antibodies were measured also in sera of 88 RA patients, 28 ReA, 14 UDA, 71 other arthritides, and in 102 healthy blood donors. Results. All SF were culture-negative for Mf, while 7 SF were positive by PCR (6/34 RA and 1/8 UDA). SF from patients with other arthritides and ReA were PCR-negative. The prevalence of anti-Mf antibodies in SF of RA patients was significantly higher than in SF of other arthritides (p = 0.01). In 47% (17/38) of all RA (including the 6 PCR-positive patients), the level of antibodies to Mf in their SF was higher than that in sera, compared to 7.5% (3/40) in other arthritides (p = 0.0002). There was no significant difference in the prevalence of serum antibodies to Mf between patients with RA, other arthritides, and healthy controls. By IB with Mf sonicate, binding to Mf peptides P107, P48, and P29 was detected in SF of 7/11 RA patients but not in 11 patients with traumatic arthritis. Specific binding to Mf membrane lipoproteins was also more prevalent in SF of RA patients than in other arthritides (p = 0.038). Conclusion. The finding that both Mf DNA and specific antibodies to Mf were present in the SF of RA patients suggests that in some RA patients Mf may play a role in initiating or perpetuating synovitis.