Quantitative Analysis and Molecular Fingerprinting of Methicillin‐Resistant Staphylococcus aureus Nasal Colonization in Different Patient Populations: A Prospective, Multicenter Study • Author(s): L. A. Mermel , DO, SM, S. J. Eells , MPH, M. K. Acharya , MD, J. M. Cartony , BS, D. Dacus , MS, S. Fadem , MD, E. A. Gay , BS, S. Gordon , MD, J. R. Lonks , MD, T. M. Perl , MD, MSc, L. K. McDougal , MS, J. E. McGowan , MD, G. Maxey , BA, D. Morse , MS, F. C. Tenover , PhD Reviewed work(s): Source: Infection Control and Hospital Epidemiology, Vol. 31, No. 6 (June 2010), pp. 592-597 Published by: The University of Chicago Press on behalf of The Society for Healthcare Epidemiology of America Stable URL: http://www.jstor.org/stable/10.1086/652778 . Accessed: 17/11/2011 12:20 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. The University of Chicago Press and The Society for Healthcare Epidemiology of America are collaborating with JSTOR to digitize, preserve and extend access to Infection Control and Hospital Epidemiology. http://www.jstor.org

infection control and hospital epidemiology june 2010, vol. 31, no. 6 o r i g i n a l a r t i c l e Quantitative Analysis and Molecular Fingerprinting of Methicillin- Resistant Staphylococcus aureus Nasal Colonization in Different Patient Populations: A Prospective, Multicenter Study L. A. Mermel, DO, SM S. J. Eells, MPH M. K. Acharya, MD J. M. Cartony, BS D. Dacus, MS S. Fadem, MD E. A. Gay, BS S. Gordon, MD J. R. Lonks, MD T. M. Perl, MD, MSc L. K. McDougal, MS J. E. McGowan, MD G. Maxey, BA D. Morse, MS F. C. Tenover, PhD objectives. To better understand the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection in different patient populations, to perform quantitative analysis of MRSA in nasal cultures, and to characterize strains using molecular fingerprinting. design. Prospective, multicenter study. setting. Eleven different inpatient and outpatient healthcare facilities. participants. MRSA-positive inpatients identified in an active surveillance program inpatients and outpatients receiving hemodialysis inpatients and outpatients with human immunodeficiency virus (HIV) infection patients requiring cardiac surgery and elderly patients requiring long-term care. methods. Nasal swab samples were obtained from January 23, 2006, through July 27, 2007 MRSA strains were quantified and char- acterized by molecular fingerprinting. results. A total of 444 nares swab specimens yielded MRSA (geometric mean quantity, 794 CFU per swab range, 3–15,000,000 CFU per swab). MRSA prevalence was 20% for elderly residents of long-term care facilities (25 of 125 residents), 16% for HIV-infected outpatients (78 of 494 outpatients), 15% for outpatients receiving hemodialysis (31 of 208 outpatients), 14% for inpatients receiving hemodialysis (86 of 623 inpatients), 3% for HIV-infected inpatients (5 of 161 inpatients), and 3% for inpatients requiring cardiac surgery (6 of 199 inpatients). The highest geometric mean quantity of MRSA was for inpatients requiring cardiac surgery (11,500 CFU per swab). An association was found between HIV infection and colonization with the USA300 or USA500 strain of MRSA ( The Brazilian clone was found P X .001). for the first time in the United States. Pulsed-field gel electrophoresis patterns for 11 isolates were not compatible with known USA types or clones. conclusion. Nasal swab specimens positive for MRSA had a geometric mean quantity of 794 CFU per swab, with great diversity in the quantity of MRSA at this anatomic site. Outpatient populations at high risk for MRSA carriage were elderly residents of long-term care facilities, HIV-infected outpatients, and outpatients receiving hemodialysis. Infect Control Hosp Epidemiol 2010 31(6):592-597 From the Warren Alpert Medical School of Brown University (L.A.M., J.R.L.) and the Division of Infectious Diseases, Rhode Island Hospital (L.A.M.), and the Division of Infectious Diseases, Miriam Hospital (J.R.L.), Providence, Rhode Island Outcomes Research International, Hudson, (M.K.A., S.F.), and Life Care Home Health Services, Delray Beach, Florida (D.D.) The Cleveland Clinic Foundation, Cleveland, Ohio (S.G.) Johns Hopkins Medical Institutions, Baltimore, Maryland (T.M.P.) 3M Infection Prevention, St. Paul, Minnesota (J.M.C., G.M., D.M.) the Department of Epidemiology, Rollins School of Public Health, Emory University (S.J.E., E.A.G., J.E.M.), and the Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention (L.K.M.), Atlanta, Georgia and Cepheid, Sunnyvale, California (F.C.T.). Received May 15, 2009 accepted December 11, 2009 electronically published April 19, 2010. 2010 by The Society for Healthcare Epidemiology of America. All rights reserved. 0899-823X/2010/3106-0006$15.00. DOI: 10.1086/652778 One in 3 individuals is colonized with Staphylococcus aureus, most often in the nares.1,2 In the United States, S. aureus is the second most common pathogen causing healthcare-as- sociated infections, 49% of which are infections caused by methicillin-resistant S. aureus (MRSA).3 USA100 is the most common strain of MRSA among healthcare-associated MRSA infections in the United States.4,5 The aims of our study were to better understand the prevalence of MRSA colonization or infection in different patient populations, to perform quantitative analysis of MRSA in nasal cultures, and to char- acterize strains using molecular fingerprinting. methods Patients were enrolled at 11 healthcare facilities from January 23, 2006, through July 27, 2007. Nasal swab samples were