MRSA in the Urban Poor • CID 2002:34 (15 February) • 425 MAJOR ARTICLE Population-Based Community Prevalence of Methicillin-Resistant Staphylococcus aureus in the Urban Poor of San Francisco Edwin D. Charlebois, 1 David R. Bangsberg, 1 Nicholas J. Moss, 1 Matthew R. Moore, 1 Andrew R. Moss, 2 Henry F. Chambers, 1 and Franc ¸ oise Perdreau-Remington 1 1 Department of Medicine, Epidemiology and Prevention Interventions Center, Division of Infectious Diseases, San Francisco General Hospital, and 2 Department of Epidemiology & Biostatistics, University of California, San Francisco The study objective was to determine the prevalence and risk factors for nasal colonization with Staphylococcus aureus and methicillin resistance among the urban poor and to compare antibiotic resistance and genetic similarity to concurrently collected clinical isolates of methicillin-resistant S. aureus (MRSA). A population- based community sample of 833 homeless and marginally housed adults were cultured and compared with 363 clinical isolates of MRSA; 22.8% of the urban poor were colonized with S. aureus. Of S. aureus isolates, 12.0% were methicillin resistant. Overall prevalence of MRSA was 2.8%. Significant multivariate risk factors for MRSA were injection drug use (odds ratio [OR], 9.7), prior endocarditis (OR, 4.1), and prior hospitalization within 1 year (OR, 2.4). Resistance to antimicrobials other than b-lactams was uncommon. Only 2 individuals (0.24%) with MRSA had no known risk factors. A total of 22 of 23 community MRSA genotypically matched clinical MRSA isolates, with 15 of 23 isolates identical to MRSA clones endemic among hospitalized patients. Recent reports of infection with methicillin-resistant Staphylococcus aureus (MRSA) in adults and children without known risk factors has led to concern that MRSA may be becoming a community-acquired path- ogen [1–5]. One of the difficulties in assessing the incidence and prevalence of community-acquired MRSA (CA-MRSA) Received 15 June 2001; revised 16 August 2001; electronically published 2 January 2002. Financial support: Centers for Disease Control and Prevention (Atlanta), California Emerging Infections Program, the University of California, San Francisco AIDS Clinical Research Program, National Institute of Mental Health, Bethesda, Maryland (grant R01-MH54907), and an unrestricted grant from Pharmacia & Upjohn, Peapack, New Jersey. E.D.C. and D.R.B. were supported in part by the Doris Duke Foundation, New York City. H.F.C. was supported in part by the USPHS and NIH/NIAID (grants AI43959 and AI46610). Reprints and correspondence: Dr. Edwin D. Charlebois, Dept. of Medicine, Division of Infectious Diseases, San Francisco General Hospital, University of California, San Francisco, 1001 Potrero Ave. UCSF 1372, Building 100, Rm. 303, San Francisco, CA 94110 (edc@epi-center.ucsf.edu). Clinical Infectious Diseases 2002; 34:425–33  2002 by the Infectious Diseases Society of America. All rights reserved. 1058-4838/2002/3404-0001$03.00 is the lack of accepted criteria for the definition of “community acquired.” It is often problematic to dif- ferentiate “health care–acquired” from true CA-MRSA, given the study design and sample populations reported in the literature. The potential establishment of MRSA infections in the community and the subsequent need to treat these infections with vancomycin raises the specter of the spread of vancomycin-resistant strains of S. aureus. This could lead to few or no treatment options for S. aureus infections. Indeed, the recent emergence of vancomycin intermediate-resistant S. aureus (VISA) in the United States and abroad is thought to have been driven by increasing vancomycin usage [6]. The single largest risk factor identified in studies else- where of CA-MRSA is hospitalization within the past 12 months [7–9]. It is also known that adults who acquire MRSA in the hospital may remain colonized for long periods of time [10, 11]. Injection drug use has also been reported to be a risk factor for CA-MRSA and carriage of S. aureus in a few urban settings [12–15]. by guest on June 1, 2016 http://cid.oxfordjournals.org/ Downloaded from