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Clinical Incidence of Methicillin-Resistant Staphylococcus aureus (MRSA) Colonization or Infection as a Proxy Measure for MRSA Transmission in Acute Care Hospitals

  • Pei-Jean I. Feng (a1), Alexander J. Kallen (a1), Katherine Ellingson (a1), Robert Muder (a2), Rajiv Jain (a2) and John A. Jernigan (a1)...



The incidence of methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection has been used as a proxy measure for MRSA transmission, but incidence calculations vary depending on whether active surveillance culture (ASC) data are included.


To evaluate the relationship between incidences of MRSA colonization or infection calculated with and without ASCs in intensive care units and non-intensive care units.


A Veterans Affairs medical center.


From microbiology records, incidences of MRSA colonization or infection were calculated with and without ASC data. Correlation coefficients were calculated for the 2 measures, and Poisson regression was used to model temporal trends. A Poisson interaction model was used to test for differences in incidence trends modeled with and without ASCs.


The incidence of MRSA colonization or infection calculated with ASCs was 4.9 times higher than that calculated without ASCs. Correlation coefficients for incidences with and without ASCs were 0.42 for intensive care units, 0.59 for non-intensive care units, and 0.48 hospital-wide. Trends over time for the hospital were similar with and without ASCs (incidence rate ratio with ASCs, 0.95 [95% confidence interval, 0.93-0.97]; incidence rate ratio without ASCs, 0.95 [95% confidence interval, 0.92-0.99]; P = .68). Without ASCs, 35% of prevalent cases were falsely classified as incident.


At 1 Veterans Affairs medical center, the incidence of MRSA colonization or infection calculated solely on the basis of clinical culture results commonly misclassified incident cases and underestimated incidence, compared with measures that included ASCs; however, temporal changes were similar. These findings suggest that incidence measured without ASCs may not accurately reflect the magnitude of MRSA transmission but may be useful for monitoring transmission trends over time, a crucial element for evaluating the impact of prevention activities.


Corresponding author

Centers for Disease Control and Prevention, 1600 Clifton Road, MS A-35, Atlanta, GA 30333 (


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1.Cosgrove, SE, Sakoulas, G, Perencevich, EN, Schwaber, MJ, Karchmer, AW, Carmeli, Y. Comparison of mortality associated with methicillin-resistant and methicillin-susceptible Staphyloccocus aureus bacteremia: a meta-analysis. Clin Infect Dis 2003;36:5359.
2.Engemann, JJ, Carmeli, Y, Cosgrove, SE, et al. Adverse clinical and economic outcomes attributable to methicillin resistance among patients with Staphyloccocus aureus surgical site infection. Clin Infect Dis 2003;36: 592598.
3.Cosgrove, SE, Qi, Y, Kaye, KS, Harbarth, S, Karchmer, AW, Carmeli, Y. The impact of methicillin resistance in Staphyloccocus aureus bacteremia on patient outcomes: mortality, length of stay, and hospital charges. Infect Control Hosp Epidemiol 2005;26:166174.
4.Centers for Medicare and Medicaid Services. 9th Statement of Work. Washington, DC: US Department of Health and Human Services, 2008. Accessed December 14, 2009.
5. US Department of Health and Human Services. HHS action plan to prevent healthcare-associated infections. Washington DC: US Department of Health and Human Services, 2009. Accessed December 14, 2009.
6.Huang, SS. Health care-associated infection: assessing the value and validity of our measures. Clin Infect Dis 2009;48:11161122.
7.Cohen, AL, Calfee, D, Fridkin, SK, et al. Recommendations for metrics for multidrug-resistant organisms in healthcare settings: SHEA/HICPAC position paper. Infect Control Hosp Epidemiol 2008;29:901913.
8.Salgado, CD, Farr, BM. What proportion of hospital patients colonized with methicillin-resistant Staphyloccocus aureus are identified by clinical microbiological cultures? Infect Control Hosp Epidemiol 2006;27:116121.
9.Eveillard, M, Lancien, E, Barnaud, G, et al. Impact of screening for MRSA carriers at hospital admission on risk-adjusted indicators according to the imported MRSA colonization pressure. J Hosp Infect 2005;59:254258.
10.Huang, SS, Rifas-Shiman, SL, Warren, DK, et al. Improving methicillin-resistant Staphyloccocus aureus surveillance and reporting in intensive care units. J Infect Dis 2007;195:330338.
11.Calfee, DP, Salgado, CD, Classen, D, et al. Strategies to prevent trans-mission of methicillin-resistant Staphyloccocus aureus in acute care hospitals. Infect Control Hosp Epidemiol 2008;29:S62S80.
12.Robicsek, A, Beaumont, JL, Paule, SM, et al. Universal surveillance for methicillin-resistant Staphyloccocus aureus in 3 affiliated hospitals. Ann Intern Med 2008;148:409418.
13.Harbarth, S, Fankhauser, C, Schrenzel, J, et al. Universal screening for methicillin-resistant Staphyloccocus aureus at hospital admission and nosocomial infection in surgical patients. JAMA 2008;299:11491157.
14.Hindler, JF, Stelling, J. Analysis and presentation of cumulative antibiograms: a new consensus guideline from the Clinical and Laboratory Standards Institute. Clin Infect Dis 2007;44:867873.
15.White, RL, Friedrich, LV, Burgess, DS, Brown, EW, Scott, LE. Effect of removal of duplicate isolates on cumulative susceptibility reports. Diagn Microbiol Infect Dis 2001;39:251256.
16.Lucet, JC, Chevret, S, Durand-Zaleski, I, Chastang, C, Regnier, B. Prevalence and risk factors for carriage of methicillin-resistant Staphyloccocus aureus at admission to the intensive care unit: results of a multi-center study. Arch Intern Med 2003;163:181188.
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Infection Control & Hospital Epidemiology
  • ISSN: 0899-823X
  • EISSN: 1559-6834
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