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Invasive Methicillin-Resistant Staphylococcus aureus Infections in the United States.
Klevens, R. Monina DDS, MPH; Morrison, Melissa A. MPH; Nadle, Joelle MPH; Petit, Susan MPH; Gershman, Ken MD, MPH; Ray, Susan MD; Harrison, Lee H. MD; Lynfield, Ruth MD; Dumyati, Ghinwa MD; Townes, John M. MD; Craig, Allen S. MD; Zell, Elizabeth R. MSTAT; Fosheim, Gregory E. MPH; McDougal, Linda K. MS; Carey, Roberta B. PhD; Fridkin, Scott K. MD; Active Bacterial Core surveillance (ABCs) MRSA Investigators
[Article] JAMA. 298(15):1763-1771, October 17, 2007.

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Context: As the epidemiology of infections with methicillin-resistant Staphylococcus aureus (MRSA) changes, accurate information on the scope and magnitude of MRSA infections in the US population is needed.

Objectives: To describe the incidence and distribution of invasive MRSA disease in 9 US communities and to estimate the burden of invasive MRSA infections in the United States in 2005.

Design and Setting: Active, population-based surveillance for invasive MRSA in 9 sites participating in the Active Bacterial Core surveillance (ABCs)/Emerging Infections Program Network from July 2004 through December 2005. Reports of MRSA were investigated and classified as either health care-associated (either hospital-onset or community-onset) or community-associated (patients without established health care risk factors for MRSA).

Main Outcome Measures: Incidence rates and estimated number of invasive MRSA infections and in-hospital deaths among patients with MRSA in the United States in 2005; interval estimates of incidence excluding 1 site that appeared to be an outlier with the highest incidence; molecular characterization of infecting strains.

Results: There were 8987 observed cases of invasive MRSA reported during the surveillance period. Most MRSA infections were health care-associated: 5250 (58.4%) were community-onset infections, 2389 (26.6%) were hospital-onset infections; 1234 (13.7%) were community-associated infections, and 114 (1.3%) could not be classified. In 2005, the standardized incidence rate of invasive MRSA was 31.8 per 100 000 (interval estimate, 24.4-35.2). Incidence rates were highest among persons 65 years and older (127.7 per 100 000; interval estimate, 92.6-156.9), blacks (66.5 per 100 000; interval estimate, 43.5-63.1), and males (37.5 per 100 000; interval estimate, 26.8-39.5). There were 1598 in-hospital deaths among patients with MRSA infection during the surveillance period. In 2005, the standardized mortality rate was 6.3 per 100 000 (interval estimate, 3.3-7.5). Molecular testing identified strains historically associated with community-associated disease outbreaks recovered from cultures in both hospital-onset and community-onset health care-associated infections in all surveillance areas.

Conclusions: Invasive MRSA infection affects certain populations disproportionately. It is a major public health problem primarily related to health care but no longer confined to intensive care units, acute care hospitals, or any health care institution.