Proteus mirabilis and rheumatoid arthritis: no association with the disease.

Proteus mirabilis (PM) is implicated in different studies in the pathogenesis of rheumatoid arthritis (RA) because of the structural homogeneity of its haemolysin B precursor with EQRRAA sequences in DRB 1 haplotype. The aim of the study was to compare the levels of antibodies specific to PM in the sera of patients with RA and healthy controls in our population. Serum samples from 78 consecutive RA patients and 75 healthy controls were analysed for the presence of IgG isotype and total immunoglobulins (IgG + IgA + IgM) against PM using enzyme-linked immunosorbent assay (ELISA) with two kinds of antigen preparations, whole bacteria and SDS-lysed bacterial extract. There was no significant increase in the concentrations of anti- Proteus antibodies (APA) in patients with RA compared to healthy controls in our population, when SDS-lysed bacterial extract or whole bacteria were used as antigen. The APA levels did not correlate with serum CRP levels. We conclude that P. mirabilis has no pathological or aggravating role in RA.