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Author Notes:

Address correspondence to Edward Stenehjem, MD, MSc, Department of Clinical Epidemiology and Infectious Diseases, Intermountain Medical Center, 5121 S. Cottonwood St, Gardner Women and Newborn Center LL2, Murray, UT 84157. eddie.stenehjem@imail.org (E. Stenehjem).

The authors thank Priscilla Maldonado-Estrada, Henry K. Lowery, Cortney Stafford, and the Atlanta VAMC clinical microbiology laboratory for their assistance.

Conflicts of interest: None to report.


Research Funding:

Educational support was provided by PHS Grant UL RR025008 from the Clinical and Translational Science Award program, National Institutes of Health, National Center for Research Resources.


  • Science & Technology
  • Life Sciences & Biomedicine
  • Public, Environmental & Occupational Health
  • Infectious Diseases
  • Staphylococcus aureus
  • Carriage quantification
  • Cycle threshold

MRSA nasal colonization burden and risk of MRSA infection


Journal Title:

American Journal of Infection Control


Volume 41, Number 5


, Pages 405-410

Type of Work:

Article | Post-print: After Peer Review


Background: Staphylococcus aureus nasal colonization burden has been identified as a risk factor for infection. This study evaluates methicillin-resistant S aureus (MRSA) nasal burden, as defined by the cycle threshold (Ct) and risk of subsequent infection. Methods: In a retrospective cohort study, United States veterans were classified into 3 MRSA nasal colonization groups: noncarriers, low burden (Ct > 24 cycles), and high burden (Ct ≤ 24 cycles). MRSA infections were identified prospectively, and clinical information was obtained by chart review. Multivariate logistic regression assessed the association of MRSA nasal burden and risk of MRSA infection. Results: During 4-years of follow-up, 4.3% of noncarriers, 18.5% of low burden, and 17.2% of high burden developed a MRSA infection. In multivariate analysis, MRSA nasal colonization was a risk factor for MRSA infection (P =.008) with low burden (risk ratio [RR], 3.62; 95% confidence interval [CI]: 1.47-8.93) and high burden (RR, 2.71; 95% CI: 0.95-7.72) associated with subsequent MRSA infection when compared with noncarriers. When compared with low burden, high burden nasal carriers were not at increased risk of infection (RR, 0.75; 95% CI 0.36-1.55). Conclusion: MRSA nasal colonization was a risk factor for MRSA infection. High nasal burden of MRSA did not increase the risk of infection.

Copyright information:

© 2013 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

This is an Open Access work distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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