Persistence of Staphylococcus aureus colonization among individuals with immune-mediated inflammatory diseases treated with TNF-α inhibitor therapy

Objective. We investigated the relationship between Staphylococcus aureus colonization and the use of immunosuppressive therapies in patients with immune-mediated inflammatory diseases (IMIDs). Methods. We prospectively enrolled IMID patients from the rheumatology and dermatology departments of Oregon Health & Science University. At enrolment, we surveyed patients for S. aureus infection risk factors and those using immune-modulating therapies, and evaluated their colonization status with bilateral nares and inguinal fold cultures. Patients were asked to follow up 6-12 months later for reassessment of colonization status by repeat culture. S. aureus isolates were tested for the presence of methicillin resistance by PCR. Results. We enrolled a total of 548 IMID patients. At enrolment, 219 (40.0%) patients were colonized with S. aureus, of which 27 (12.3%) were methicillin-resistant S. aureus (MRSA). Baseline colonization rates were similar between TNF-alpha inhibitor users and non-users (40.5% and 39.4%, P = 0.79), but were significantly higher for psoriasis patients compared with those with RA (43.5% and 31.8%, P = 0.02). A total of 384 patients were available for follow-up. Patients who were colonized at enrolment were more likely to be colonized at follow-up if they were treated with TNF-alpha inhibitors during the study as compared to patients without TNF-alpha inhibitor exposure [odds ratio (OR) = 2.2 (95% CI 1.1, 4.2), P = 0.02]. Conclusion. Patients with psoriasis are more likely to be colonized with S. aureus than patients with RA. Patients who are colonized with S. aureus are more likely to remain colonized if exposed to TNF-alpha inhibitors.