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. 2013 May;41(5):405-10.
doi: 10.1016/j.ajic.2012.07.017. Epub 2012 Dec 20.

MRSA nasal colonization burden and risk of MRSA infection

Edward Stenehjem  1 , David Rimland
Affiliations

MRSA nasal colonization burden and risk of MRSA infection

Edward Stenehjem et al. Am J Infect Control. 2013 May.

Abstract

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.

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Conflict of interest statement

Conflicts of interest: None to report.

Figures

Fig 1
Fig 1
Distribution of the cycle threshold (CT) among patients with positive admission nasal MRSA screening (Xpert MRSA assay) in Atlanta veterans (n = 205).
See this image and copyright information in PMC

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