Fact, fiction, or no data: what does surveillance for methicillin-resistant Staphylococcus aureus prevent in the intensive care unit?

The polarizing debate about how to control antimicrobial-resistant organisms in hospitals continues to focus on methi-cillin-resistant Staphylococcus aureus (MRSA) and the use of active surveillance cultures. In the United States, MRSA infection causes an estimated 18,650 deaths annually among hospitalized patients [1] and likely cost billions of dollars [2]. The National Nosocomial Infections Surveillance system of the Centers for Disease Control and Prevention reported that, by 2003, 160% of the S. aureus isolates causing nosocomial infections in US hospitals were methicillin resistant [3]. Compared with infections due to methicillin-susceptible strains of S. aureus, infections due to MRSA are associated with poorer clinical outcomes [4] and increased health care costs [5]. Because the prevalence of MRSA is increasing in hospitals, efforts to control MRSA are gaining more public attention. The control of MRSA in the intensive care unit (ICU) is supported by 2 principal ep-idemiologic findings: higher MRSA colo-nization rates increase the risk for MRSA transmission between hospitalized patients [6], and MRSA colonization is a significant risk factor for developing a subsequent MRSA infection [7–9]. An estimated 19% of patients who are colonized with MRSA at the time of admission to an ICU will develop MRSA infection, and 25% of those who acquire MRSA col-onization while in the ICU may later develop MRSA infection [8]. Given the increased risk of infection in colonized patients , preventing transmission of MRSA between patients is predicted to reduce hospital-acquired MRSA colonization and subsequent infections. Active surveillance cultures (ASCs) are a contentiously debated strategy for prevention of MRSA transmission in hospitals. ASCs incorporates screening patients at the time of admission to a hospital unit to identify MRSA carriers (prevalent carriers) followed by periodic screening in the unit to identify people who acquire MRSA colonization while in the ICU (incident cases). The premise of ASCs lies in detecting patients who are asymptomatically colonized with multidrug-resistant bacteria , such as MRSA, and who can be isolated from other patients. The Society for Healthcare Epidemiology of America published guidelines in 2003 supporting ASCs, in combination with other basic infection control practices, to identify MRSA-colonized patients [10]. The Center for Disease Control and Prevention's Health-care Infection Control Practices Advisory Committee offered a more conservative recommendation of ASCs as a second tier for preventing transmission after baseline infection control measures fail [11]. Generally, a screening program targets a person at risk who can be offered an intervention to prevent a …