Nasal Carriage of enterotoxigenic Staphylococcus aureus and microRNA 146a expression profile in rheumatoid arthritis patients.

Rheumatoid arthritis (RA) is a chronic autoimmune disease of multifactorial etiology which is linked to interactions between host and environmental factors. Previous studies showed that nasal carriage of the enterotoxigenic Staphylococcus aureus and increased expression of micro RNA-146a (miRNA-146a) may have a role in RA pathogenesis and severity. The objectives of this study were to evaluate the prevalence of nasal colonization by the enterotoxigenic S. aureus in RA patients and to correlate serum levels of staphylococcal enterotoxin and miRNA-146a relative expression in all the study participants with disease severity in RA patients. In this case-control study, after S. aureus isolation from nasal swabs of all participants, the prevalence of nasal colonization by enterotoxigenic S. aureus was assessed by the enzyme-linked immunosorbent assay (ELISA). Also, serum staphylococcal enterotoxin level was measured by ELISA. The quantitative reverse transcription polymerase chain reaction was used to assess serum miRNA-146a relative expression level. Assessment of RA disease activity was achieved according to the Disease Activity Score in 28 joints (DAS 28). Enterotoxigenic nasal S. aureus carriage rate was significantly higher in RA patients than control subjects (p < 0.001). RA patients showed a significantly higher mean value of serum levels of staphylococcal enterotoxin and miRNA-146a relative expression when compared to controls (p < 0.001 for both) and the highest mean value of both were found in RA patients with high disease activity (p < 0.001). There was a significant positive correlation between the relative expression level of miRNA-146a and serum level of staphylococcal enterotoxin in RA patients. In conclusion, staphylococcal enterotoxins and miRNA-146a could have a significant role in RA pathogenesis and both correlate with disease activity.