National prevalence of methicillin-resistant Staphylococcus aureus in inpatients at United States health care facilities, 2010

Background: Methicillin-resistant Staphylococcus aureus (MRSA) remains one of the most prevalent multidrug-resistant organisms causing health care-associated infections. Limited data are available about how the prevalence of MRSA has changed over the past several years and what MRSA prevention practices have been implemented since the 2006 Association for Professionals in Infection Control and Epidemiology, Inc, MRSA survey. Methods: We conducted a national prevalence survey of MRSA colonization or infection in inpatients at US health care facilities. The survey was developed, received institutional review board approval, and then was distributed to all US Association for Professionals in Infection Control and Epidemiology, Inc, members. Members were asked to complete the survey on 1 day during the period August 1 to December 30, 2010, reporting the number of inpatients with MRSA infection or colonization and facility- and patient-specific information. Results: Personnel at 590 facilities indicated a state and responded to the survey. All states were represented, except for Alaska and Washington, DC (mean, 12 facilities per state; range, 1-38). Respondents reported 4,476 MRSA-colonized/infected patients in 67,412 inpatients; the overall MRSA prevalence rate was 66.4 per 1,000 inpatients (25.3 infections and 41.1 colonizations per 1,000 inpatients). Active surveillance testing was conducted by 75.7% of the respondents; 39.6% used nonselective media, 37.2% used selective media, and 23.3% used polymerase chain reaction. Detailed data were provided on 3,176 MRSA-colonized/infected patients. Of those in whom colonization/infection status was reported (1,908/3,086 [61.8%] were MRSA colonized and 1,778/3,086 [38.2%] were MRSA infected), most MRSA-colonized or infected patients (78.3%) were detected within 48 hours of admission; the most common site of infection was skin and soft tissue (42.9%); and, using the Centers for Disease Control and Prevention's definitions, approximately 50% would be classified as health care-associated infections. Conclusion: Our survey documents that the MRSA prevalence in 2010 is higher than that reported in our 2006 survey. However, the majority of facilities currently are performing active surveillance testing, and, compared with 2006, the rate of MRSA infection has decreased while the rate of MRSA colonization has increased. In addition, compared with 2006, the proportion of MRSA strains recovered from MRSA-colonized/infected patients that are health care-associated strains has deceased, and community-associated strains have increased.