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MRSA nasal colonization burden and risk of MRSA infection

Edward Stenehjem1, David Rimland

  • 1Atlanta Veterans Affairs Medical Center, Decatur, GA, USA. eddie.stenehjem@imail.org

American Journal of Infection Control
|December 25, 2012
PubMed
Abstract

Insights

Methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization increases infection risk. However, high MRSA nasal burden does not further elevate this risk compared to low burden colonization.

Area of Science:

  • Infectious Diseases
  • Microbiology
  • Epidemiology

Background:

  • Staphylococcus aureus nasal colonization is a known risk factor for infection.
  • Methicillin-resistant Staphylococcus aureus (MRSA) nasal burden, quantified by cycle threshold (Ct), is evaluated as a predictor of infection.
  • Understanding MRSA colonization levels can inform infection prevention strategies.

Purpose of the Study:

  • To assess the association between MRSA nasal colonization burden and the risk of subsequent MRSA infection.
  • To determine if high MRSA nasal burden poses a greater infection risk than low burden.

Main Methods:

  • Retrospective cohort study of United States veterans.
  • Classification into non-carrier, low burden (Ct > 24), and high burden (Ct ≤ 24) MRSA nasal colonization groups.
  • Prospective identification of MRSA infections and chart review, analyzed using multivariate logistic regression.

Main Results:

  • MRSA nasal colonization was a significant risk factor for MRSA infection (P = .008).
  • Low burden colonization (RR, 3.62) and high burden colonization (RR, 2.71) increased infection risk compared to non-carriers.
  • High burden nasal carriers did not have a statistically significant increased risk of infection compared to low burden carriers (RR, 0.75).

Conclusions:

  • MRSA nasal colonization is a confirmed risk factor for developing MRSA infections.
  • The level of MRSA nasal burden (high vs. low) did not significantly alter the risk of subsequent infection.

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