Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Colonization and Infection by Staphylococcus Aureus among Those Using Biologic Therapy.

Varley1,  Cara, Deodhar1,  Atul A., Ehst1,  Benjamin, Bakke1,  Antony, Blauvelt1,  Andrew, Vega2,  Robert, Winthrop1,  Kevin

Oregon Health & Science University, Portland, OR
Oregon State Public Health Laboratory, Hillsboro, OR

Purpose:

While much emphasis has been placed on preventing opportunistic infections in patients with inflammatory arthritis on biologic therapy, it is clear that most serious infections are due to "routine" organisms like Staphylococcal aureus. In an ongoing prospective study we investigated the relationship between rates of new and persistent colonization, new infections with S. aureus, use of biologics and underlying disorder.

Methods:

We prospectively enrolled patients with autoimmune inflammatory diseases from the rheumatology and dermatology clinics of our University. Patients receiving or being considered for biologic therapy (etanercept, infliximab, adalimumab, rituximab, abatacept) were surveyed for the presence of S. aureus infection risk factors and assessed for S. aureus colonization. Specimens collected from the bilateral nares and inguinal folds were cultured using standardized laboratory isolation procedures and screened for the presence of methicillin-resistant S aureus (MRSA) utilizing Spectra™ MRSA test media (Remel Scientific®) and mannitol salt agar containing 4 mcgs of oxacillin (MSAO, Remel Scientific). We actively sought to follow up patients to assess persistence of colonization, new colonization, or infections with S. aureus, and their relationship with underlying disease and therapy.

Results:

We enrolled a total of 392 patients (rheumatoid arthritis n=103 (26.3%), psoriasis or psoriatic arthritis n=205 (52.3%), ankylosing spondylitis n=29 (7.4%), combination of two or more n=15 (3.8%), other n=40 (10.2%). At baseline, 156 (39.8%) were colonized with S. aureus, of which 19 (12.2%) had MRSA. Our baseline colonization rates of S. aureus (39.8%) and MRSA (4.8%) were significantly higher than previously reported for the general population (30.8% and 0.8%, p<0.01 for both). Colonization rates were similar between biologic users and non-users (40.1% and 39.5%, p=0.90) but were significantly higher for psoriasis patients compared to those with RA (43.4% and 30.1%, p=0.02). 184 patients, of which 122 (66.3%) were on biologic therapy, completed follow up (mean 1 year, range 0.2–2.3 years). Biologic agents did not increase the risk of persistent (colonized at baseline and follow up) or new colonization (see table). Self reported infections were more common in persistently colonized patients compared to those newly, transiently or never colonized (RR=4.25, 95% CI 0.99–18.25, p=0.05).

Conclusion:

Inflammatory arthritis patients at our center have higher rates of S. aureus colonization than the general population, and the risk of new colonization is not modified by biologic therapy. Prospective follow up shows a trend towards increased risk of subsequent infections in those with persistent S aureus colonization.

Colonization and Self Reported Staph Infections at Follow-up, N = 184

 Persistent Staph ColonizationNo Staph ColonizationSelf Reported Staph Infection
Anti-TNF Exposure Between Enrollment and Follow-up33¥625*
 27.05%50.82%4.20%
No Anti-TNF Exposure Between Enrollment and Follow-up10¥342*
 16.13%54.84%3.28%
Rheumatoid Arthritis11310
 22.92%64.58%0.00%
Psoriasis and/or Psoriatic Arthritis22495
 22.00%49.00%5.05%
Ankylosing Spondylitis540
 38.46%30.77%0.00%
Othern380
 18.75%50.00%0.00%
Two or More242#
 28.57%57.14%28.57%
¥ No statistically significant association between anti-TNF exposure and persistent staph colonization, p = 0.15
* No statistically significant association between anti-TNF exposure and self reported staph infections, p = 1.00
n Includes Crohn's Disease, Ulcerative Colitis, Uveitis
# Both patients had a psoriasis diagnosis

To cite this abstract, please use the following information:
Varley, Cara, Deodhar, Atul A., Ehst, Benjamin, Bakke, Antony, Blauvelt, Andrew, Vega, Robert, et al; Colonization and Infection by Staphylococcus Aureus among Those Using Biologic Therapy. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :758
DOI: 10.1002/art.28526

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