Increased Staphylococcus aureus Nasal Carriage Rates in Rheumatoid Arthritis Patients on Biologic Therapy.

BACKGROUND

Rheumatoid arthritis patients are at increased risk for periprosthetic joint infection after arthroplasty. The reason is multifactorial. Nasal colonization with Staphylococcus aureus is a modifiable risk factor; carriage rates in RA patients are unknown. The goal of this study is to determine the S aureus nasal carriage rates of RA patients on biologics, RA patients on traditional disease-modifying anti-rheumatic drugs (DMARDs), and osteoarthritis.

METHODS

Consecutive patients with RA on biologics (±DMARDs), RA on non-biologic DMARDs, or OA were prospectively enrolled from April 2017 to May 2018. One hundred twenty-three patients were determined necessary per group to show a difference in carriage rates. Patients underwent a nasal swab and answered questions to identify additional risk factors. S aureus positive swabs were further categorized using spa typing. Logistic regression evaluated the association with S aureus colonization between the groups after controlling for known risk factors.

RESULTS

RA patients on biologics, 70% of whom were on DMARDs, had statistically significant increase in S aureus colonization (37%) compared to RA on DMARDs alone (24%), or OA (20%) (P = .01 overall). After controlling for glucocorticoids, antibiotic use, recent hospitalization, and diabetes, RA on biologics had a significant increased risk of S aureus nasal colonization (Odds ratio 1.80, 95% confidence interval 1.00-3.22, P = .047).

CONCLUSION

S aureus colonization risk was increased for RA on biologics compared to RA not on biologics and OA. Nasal S aureus carriage increases the risk of surgical site infection; this modifiable risk factor should be addressed prior to total joint arthroplasty for this higher risk patient group.