Methicillin-Resistant : What Is the Best Prevention Strategy?*Staphylococcus aureus: What Is the Best Prevention Strategy?* Infection in ICU: What Is the Best Prevention Strategy?*

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Staphylococcus aureus is a major human pathogen. The resistance to celbenin, a penicillinase-resistant penicillin or methicillin, was first reported in 1961 and has been on the rise since then. Methicillin resistance is measured by oxacillin, methicillin, or cefoxitin sensitivity. Methicillin resistance is mediated by a penicillin-binding protein 2a and requires the presence of the mec gene, part of the staphylococcal cassette chromosome. Estimated prevalence of methicillin-resistant S. aureus (MRSA) ranges between 8% and 14%, depending on the geographic location and type of testing used (1). Healthcare-associated infections (HAIs) remain an important health burden (2). An infection acquired during ICU stay can be associated with doubling of treatment cost and prolonged hospitalization (3). MRSA is one of the leading causes of both HAI and community-associated infection. Fifty-three percent of pathogens from device-associated infections, including MRSA, come from adult critical care units within acute care hospitals (4). For the period 2011–2014, the antimicrobial resistance patterns for HAIs reported to the Centers for Disease Control and Prevention’s National Healthcare Safety Network indicated that S. aureus (12%) was the second most common pathogen behind Escherichia coli (15%) (4). The percentage of methicillin resistance varied by HAI but remained high; in 2014, 51% central line–associated bloodstream infections, 52% catheter-associated urinary tract infections, 42% ventilator-associated pneumonias, and 43% surgical site infections were caused by MRSA (4). Furthermore, methicillin resistance confers higher morbidity and mortality, and therefore, prevention and control of MRSA transmission and infection are important.
In 2014, the Society for Healthcare Epidemiology of America in collaboration with the Infectious Diseases Society of America, the American Hospital Association, the Association for Professionals in Infection Control and Epidemiology, and The Joint Commission published an updated document on the strategies to prevent MRSA transmission and infection in acute care hospitals (5). These strategies include MRSA risk assessment, education, infection control measures, monitoring program, reporting, and accountability. If MRSA is not controlled with these strategies, special approaches may include active surveillance, decolonization (universal or targeted), universal gown and glove use, or additional special approaches. The data on the best approach to MRSA reduction have been mixed. Active screening for MRSA and decolonization in ICU settings has been associated with a decrease in MRSA infections, mortality, and medical costs (6). In a prospective, interventional study, using a case-control design, compared with targeted screening, universal screening increased the rate of detection of MRSA upon hospital admission but did not significantly reduce the rate of hospital-acquired MRSA infection and was associated with higher costs of care (7). In a pragmatic, cluster-randomized trial, universal decolonization was more effective than targeted decolonization or screening and isolation in reducing rates of MRSA clinical isolates and bloodstream infection (8). In a subsequent cost-effectiveness, decision-analysis model, the same authors demonstrated that, compared with screening and isolation, universal decolonization was estimated to save $171,000 and prevent nine additional bloodstream infections for every 1,000 ICU admissions (9). Individualized bundling infection control measures have also shown to improve quality of care and reduce cost (10).
In this issue of Critical Care Medicine, Whittington et al (11) performed another cost analysis of three prevention strategies for MRSA. Using a Markov model in a hypothetical cohort of adults admitted to the ICU followed up for 1 year, they found that universal and targeted decolonization were less costly and more effective than screening and isolation. When compared with targeted decolonization, universal decolonization was cost saving to cost effective, with maximum cost savings occurring when a hospital uses more expensive screening tests like polymerase chain reaction.

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