Abstract
Introduction
Patients with rheumatoid arthritis (RA) have a higher risk of surgical site infection (PJI) than patients with osteoarthritis (OA). Disease modifying therapy is in widespread use in RA patients, and biologic medications may increase Staphylococcus aureus colonization rates. Because S. aureus colonization likely increases risk of surgical infection, perioperative assessments and therapies to decrease the risk of invasive S.aureus infections may be warranted. The objective of this study was to determine if there was a difference in S. aureus carriage among patients with RA, OA, and RA on biologics (RA+B).
Methods
An a priori power analysis determined 123 participants per group were needed to detect a relative difference of 20% among groups with 80% power. After IRB approval, patients were screened; included patients met American College of Rheumatology classification criteria. Patients were approached between April 2017 and May 2018 and asked to perform a nasal swab while on site using the Center for Disease Control's swabbing protocol; questionnaires pertaining to their current health status were collected. Swabs were inoculated onto ChromAgar/ChromID MRSA plates for detection of S. aureus. Mann-Whitney U and Chi-square tests were used to evaluate baseline differences between groups. Logistic regression evaluated the associations between groups and S. aureus carriage. All statistical analyses were performed using SAS Software version 9.3 (SAS Institute, Cary, NC); statistical significance was defined as p<0.05.
Results
Overall the patient cohort evaluated had a mean age of 66 (+/-13.7), BMI of 29 (+/-28.2), and were predominantly female (78%) .28% of the cohort was on antibiotics within three months prior to the nasal swab, 18% were currently on steroids, and 24% had been hospitalized within the last year. We found differences in age (p<0.001), BMI (p<0.001), sex (p<0.001), diabetes (p=0.04), steroid use (p=0.02), antibiotic use (p<0.001), and hospitalizations within the last year (p<0.001). S. aureus carriage was most prevalent in RA+B37%, followed by RA (24%), and OA (20%). After multivariate adjustment, RA+B was found to have increased odds of S. aureus (OR=1.80, 95% CI 1.00–3.22); p=0.047) compared to RA group. Use of glucocorticoids, hospitalization, or diabetes did not increase the odds of S. aureus carriage. The OA group had decreased odds of S. aureus growth when compared to the RA group; however, this was not found to be statistically significant (p=0.987).
Conclusion
RA patients treated with biologics have an increased prevalence of S. aureus colonization. Since nasal S. aureus carriage may play a role in the pathogenesis of surgical infections, S. aureus decolonization should be considered in RA patients on biologics prior to elective surgery.
