Staphylococcal Enterotoxin C in Synovial Fluid of Patients With Rheumatoid Arthritis

Background: In the previous studies using the commercial ELISA kit, the existence of staphylococcal superantigens has been reported in synovial fluid of patients with rheumatoid arthritis (RA). Objectives: This study aimed to design molecular methods to detect staphylococcal enterotoxin C in synovial fluid of patients with rheumatoid arthritis. Materials and Methods: In this experimental study, Staphylococcus aureus strain producing enterotoxin C was used as the reference strain. The polymerase chain reaction (PCR) was set up by design a specific pair of primers. Besides bacterial culture, 50 synovial fluid samples of patients with rheumatoid arthritis were subjected to DNA extraction, and then PCR amplification was carried out according to the protocol. All samples were examined by ELISA method for enterotoxin C. The data were descriptively analyzed. Results: The results of bacterial culture were negative for all samples. The results showed that 66% (33 cases) of samples contained entC gene and only 46% (23 cases) have also enterotoxin C. The interesting finding was that the results of ELISA and PCR were the same and have shown only 22 positive cases (44% samples) for staphylococcal enterotoxin C. Conclusions: Based on the findings of this study, S. aureus enterotoxin C (SEC) has been detected in synovial fluid of patients with rheumatoid arthritis by PCR and ELISA methods. These valuable findings may describe the exact etiology of the RA and as well as change the methods of its diagnosis and treatment. This is the first research, which has shown the staphylococcal entC gene in synovial fluid of RA patients. However, S. aureus strains can produce more than 20 types of enterotoxins. Therefore, its involvement on rheumatoid arthritis pathogenesis makes an important challenge in the future. In this regard, further investigation on the other enterotoxins is necessary.