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Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Carriage in Residents of Veterans Affairs Long-Term Care Facilities: Role of Antimicrobial Exposure and MRSA Acquisition
Nimalie D. Stone MD, Donna R. Lewis MSN, Theodore M. Johnson II MD, Thomas Hartney MD, Doris Chandler MSN, Johnita Byrd-Sellers, John E. McGowan Jr MD, Fred C. Tenover PhD, John A. Jernigan MD, Robert P. Gaynes MD and for the Southeast Veterans Affairs Long-Term Care Methicillin-Resistant Staphylococcus aureus Cooperative
Infection Control and Hospital Epidemiology
Vol. 33, No. 6 (June 2012), pp. 551-557
Published by: Cambridge University Press on behalf of The Society for Healthcare Epidemiology of America
Stable URL: http://www.jstor.org/stable/10.1086/665711
Page Count: 7
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Objective. To identify risk factors associated with methicillin-resistant Staphylococcus aureus (MRSA) acquisition in long-term care facility (LTCF) residents.Design. Multicenter, prospective cohort followed over 6 months.Setting. Three Veterans Affairs (VA) LTCFs.Participants. All current and new residents except those with short stay (<2 weeks).Methods. MRSA carriage was assessed by serial nares cultures and classified into 3 groups: persistent (all cultures positive), intermittent (at least 1 but not all cultures positive), and noncarrier (no cultures positive). MRSA acquisition was defined by an initial negative culture followed by more than 2 positive cultures with no subsequent negative cultures. Epidemiologic data were collected to identify risk factors, and MRSA isolates were typed by pulsed-field gel electrophoresis (PFGE).Results. Among 412 residents at 3 LTCFs, overall MRSA prevalence was 58%, with similar distributions of carriage at all 3 facilities: 20% persistent, 39% intermittent, 41% noncarriers. Of 254 residents with an initial negative swab, 25 (10%) acquired MRSA over the 6 months; rates were similar at all 3 LTCFs, with no clusters evident. Multivariable analysis demonstrated that receipt of systemic antimicrobials during the study was the only significant risk factor for MRSA acquisition (odds ratio, 7.8 [95% confidence interval, 2.1–28.6]; ). MRSA strains from acquisitions were related by PFGE to those from a roommate in 9/25 (36%) cases; 6 of these 9 roommate sources were persistent carriers.Conclusions. MRSA colonization prevalence was high at 3 separate VA LTCFs. MRSA acquisition was strongly associated with antimicrobial exposure. Roommate sources were often persistent carriers, but transmission from roommates accounted for only approximately one-third of MRSA acquisitions.
© 2012 by The Society for Healthcare Epidemiology of America. All rights reserved.