Heads I Win, Tails You Lose: Modifying the Impact of MRSA After Hospital Discharge

Becky A. Smith, MD; Lance R. Peterson, MD


March 04, 2015

Editorial Collaboration

Medscape &

Health Care-Associated Methicillin-resistant Staphylococcus aureus Infections Increases the Risk of Postdischarge Mortality

Nelson RE, Stevens VW, Jones M, Samore MH, Rubin MA
Am J Infect Control. 2015;43:38-43


Universal Screening and Decolonization for Control of MRSA in Nursing Homes: A Cluster Randomized Controlled Study

Bellini C, Petignat C, Masserey E, et al
Infect Control Hosp Epidemiol. 2015 Jan 12. [Epub ahead of print]


Taking Aim at MRSA Colonization and Infection

Two new large studies highlight the negative long-term impact of methicillin-resistant Staphylococcus aureus (MRSA) healthcare-associated infection (HAI), and the failure of traditional infection control practices in lowering colonization prevalence during a stay in a long-term care facility (LTCF). Because colonization with MRSA is the greatest risk factor for MRSA clinical infection,[1] a critical question to ask is whether a successful strategy for reducing MRSA colonization, infection, and potential increased mortality outside of the hospital is possible, especially in LTCFs. Or is losing the wager that "we can do better" inevitable?

The first study consisted of 370,000 patients with inpatient admission between October 1, 2007, and September 30, 2010, from 123 US Department of Veterans Affairs hospitals. Investigators constructed multivariable Cox proportional hazard regressions to assess the impact of a positive culture on postdischarge mortality for 365 days. In addition to comparing the impact of MRSA HAI with all patients without MRSA, the investigators performed a propensity score matching process, in which adequate matches were identified for all but seven of the 3599 patients with MRSA infection.

In the full cohort, patients with MRSA were 42% more likely to die (adjusted hazard ratio, 1.42; 95% confidence interval [CI], 1.32-1.53; P < .001). This difference was maintained in the propensity-matched cohort, where a positive MRSA HAI increased the risk by 46% (95% CI, 1.21-1.77).

This study has limitations in that some cultures probably represented colonization rather than infection, but the investigators stratified the results with treatment data to minimize that effect. It also has significant strengths that result from the large data set across the United States. The investigators justifiably concluded that patients with a positive MRSA culture are at an increased risk for death compared with patients without a positive culture, even after hospital discharge, which underscores the importance of interventions designed to reduce MRSA transmission.

The second study attempted to lower MRSA colonization prevalence in a large nursing home cohort using a prospective, cluster randomized trial between June 2010 and December 2011 in the state of Vaud, Switzerland. Three prevalence studies in Vaud found MRSA in LTCFs increasing from 4.5% of residents in 2003 to 12% in 2008, thus leading investigators to perform an intervention trial.

Using a computer-generated code, the 104 participating LTCFs were randomly allocated to either the intervention group (universal MRSA screening and topical decolonization of carriers plus disinfection of the environment, along with standard precautions) or the control group (standard precautions alone, consisting of private rooms and hand hygiene). Screening for MRSA carriage was done at study entry and 12 months thereafter. In addition, all newly admitted or readmitted residents underwent MRSA screening.

The mean compliance with the MRSA screening program was 87% (range, 20%-100%) and 86% (range, 27%-100%) in the intervention and control facilities, respectively. This outcome was unexpected, in that the mean prevalence declined significantly, by 3% in the intervention LTCFs and 2.3% in the control facilities; this corresponded to a nonsignificant 0.7-percentage point reduction attributable to the intervention (P = 0.66). Low screening compliance in some facilities may have negatively affected the outcome, as did the observation that colonization rates at the onset of the study were lower than anticipated. This finding suggests that MRSA prevalence may have been declining independently, which confounded the outcome of this investigation.


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