Background: This paper presents the results of continued research on specific antibacterial antibodies, which are useful in the diagnosis of musculoskeletal diseases of suspected Gram-negative bacterial origin: Yersinia enterocolitica/pseudotuberculosis, Chlamydia trachomatis and Chlamydophila pneumoniae.
Material and methods: The study included 159 positive sera in ELISA screening test of anti-Yersinia spp. antibodies (IgA and/or IgG class) and 38 positive sera of anti-Chlamydia trachomatis antibodies (IgA and/or IgG class). They were confirmed by Western blot, with specific recombinant antigens for these microorganisms. The presence of specific antibodies against Yersinia spp. and Chlamydia trachomatis and/or Chlamydophia pneumoniae (Fig. 1, 2) was confirmed in about 60% of positive sera in ELISA for IgA class and in 75% for IgG class.
Results: Detailed analysis showed that the most common antibodies to recombinant antigens were YOP D for Yersinia spp., for both IgA (98.9%) and IgG (95.3%) class (Fig. 3) and MOMP for Chlamydia trachomatis (Fig. 6) and Chlamydophia pneumoniae (Fig. 7) in the IgA and IgG class (about 85–100%). Unexpected results for anti-Chlamydia spp. antibodies confirmed by Western blot were obtained. It was disclosed that in about 56% of sera were confirmed anti-Chlamydia trachomatis and anti-Chlamydophila pneumoniae antibodies at the same time. This may indicate previous infection or contact with these two species of microorganisms and the antibodies’ cross-reactivity (Fig. 4a, 4b).
Discussion: The obtained results indicate how important is the confirmation by Western blot of Yersinia and Chlamydia spp. infection, due to the high specificity of the Western blot test. It should also be remembered that the serological diagnosis of reactive and undifferentiated arthritis of suspected bacterial origin has to be always in close correlation with the clinical picture and carefully conducted medical history.
Conclusions: The reliability of the serological findings requires additional confirmation of the prevalence of specific antibodies to particular microorganisms in serum and/or circulating immune complexes (CIC). It points to the need for further research in this field that has been already initiated.