Rheumatoid Arthritis Increases Mortality Risk in Staphylococcus aureus Infections
Staphylococcus aureus bacteria, enmeshed within the pseudopodia of a red-colored human white blood cell. Image Credit: National Institute of Allergy and Infectious Diseases.
Patients with rheumatoid arthritis (RA) suffering from Staphylococcus aureus infection have more complications and higher mortality rates than patients without RA, according to a study published in the Journal of Infection.
The increased risk of severe infections in patients with RA is well established, but outcomes related to infections by specific pathogens in this population remain largely unexplored. S aureus infection can range in severity from uncomplicated skin infection to potentially lethal bacteremia, which carries a 30-day mortality rate of up to 30%. Although RA has not been shown to predict mortality in S aureus bacteremia (SAB), limited data suggest that patients with RA are at higher risk for S aureus-related osteoarticular infections than patients who do not have RA.
Researchers, led by Insa Joost, MD, from University Medical Center Freiburg in Germany, compared the clinical characteristics and outcomes of SAB in patients with RA vs patients without RA in a post-hoc analysis of INSTINCT (INvasive STaphylococcus aureus INfections CohorT), a prospective cohort study.
High-Yield Data Summary
- Patients with RA are a highly vulnerable group for severe courses of S aureus bacteremia.
Of 1069 patients with SAB, 31 had RA. Compared with patients without RA, patients with RA were more likely to have septic shock (39% vs 23%; P =.049) or disseminated infection (39% vs 16%; P =.002). Patients with RA also had higher rates of osteoarticular infection (48% vs 15% of patients without RA; P <.001) and were more likely to experience multiple osteoarticular infections (23% vs 6% of patients without RA; P =.002).
Although the incidence of endocarditis was similar in both groups, more patients with RA required surgical management than patients without RA (61% vs 28%).
Mortality at 30 days was significantly higher in patients with RA than in patients without RA (36% vs 19%; P =.034). Increased mortality rates in patients with RA continued to persist at 90 days and 1 year.
RA was an independent predictor of mortality (hazard ratio, 2.3). Other risk factors for mortality included use of immunosuppressive agents, age, severe sepsis, and septic shock.
In addition, RA was identified as a risk factor for osteoarticular infection (odds ratio, 4.2). Immunosuppressive treatment did not increase the risk for osteoarticular infection or disseminated infection in either group.
Summary and Clinical Applicability
Patients with RA are at increased risk for severe infection, but the clinical course and outcomes of infection in this population have not been well studied. In a prospective cohort study, researchers found that in patients with SAB, patients with RA were more likely to experience severe complications and had higher mortality rates than patients without RA.
“Further studies with larger patient cohorts are needed to assess the impact of certain immunosuppressive drugs (eg, biologicals). It would also be interesting to evaluate if other bacteria display a similar osteoarticular tropism like the one we found for S. aureus,” Dr Joost told Rheumatology Advisor.
- Only a small number of patients with RA were included in this study
- RA disease activity was not measured but may have affected clinical course and outcomes in the group of patients with RA
The researchers report financial relationships with Pfizer, MSD Sharp & Dohme, Astellas, Basilea, Novartis, AstraZeneca, Cubist, Tetraphase, The Medicines Company, BD Biosciences, bioMérieux, Limbach Gruppe SE, ViiV Healthcare, and Janssen-Cilag.
Joost I, Kaasch A, Pausch C, et al. Staphylococcus aureus bacteremia in patients with rheumatoid arthritis - data from the prospective INSTINCT cohort [published online March 18, 2017]. J Infect. doi:10.1016/j.jinf.2017.03.003