Methiciilin.resistant Staphylococcus aureus outbreak: A consensus panel's definition and management guidelines Richard P. Wenzel, MD, MSc a David R. Reagan, MD, PhD b Joseph S. Bertino, Jr, PharmD, FCCP c Ellen Jo Baron, PhD d Kathleen Arias, MS, CIC, e Richmond, Virginia, Mountain Home, Tennessee, Cooperstown, New York, los Angeles, California, and Baltimore, Maryland Objective: To provide medical personnel with a definition of an outbreak of methicillin- resistant Staphylococcus aureus (MRSA) and guidelines for managing potential outbreaks. Participants: Eighteen panel members were chosen from different specialties, types of insti- tutions, and geographic regions. Representatives from the American Society of Consultant Pharmacists, the American Society of Health-Systems 'Pharmacists, the Society for Heahhcare Epidemio!ogy of America, and the National Association of Directors of Nursing Administration participated. Consensus process: In preparation for the conference, panel members reviewed the litera- ture and wrote abstracts outlining their personal opinions on the core issues, which were circulated to all participants. During a weekend conference, the panel summarized the reviewed literature, defined an MRSA outbreak, and developed management guidelines. Evidence: Published literature, clinical experience, and expert opinion concerning the emergence and subsequent management of MRSA cases in health care institutions. Results: An outbreak of MRSA was defined as either an increase in the rate of MRSA cases or a clustering of new cases due to the transmission of a single microbial strain in the health care institution. An increased rate of cases can be defined statistically or experien- tially and includes both infected and colonized patients. A potential outbreak should trig- ger stepwise, multidisciplinaryactions consisting of basic epidemiologic procedures (phase I) to form an initial epidemiologic hypothesis of an outbreak (phase II) followed by a stan- dard epidemiologic workup (phase III) and microbiologic studies (phase IV) to confirm the hypothesis. Mupirocin calcium treatments should be considered to decolonize health care workers during the fourth phase, even before typing is completed. Conclusions: Until studies can be conducted to delineate the effectiveness of different recommendations, the proposed guidelines may provide a useful starting point that can be adapted to meet an individual institution's specific needs. (AJIC Am J Infect Control 1998;26:102-10) From the Medical College of Virginia, Virginia Commonwealth University, Richmond;a East Tennessee State University and Veterans Affairs Medical Center, Mountain Home; b Bassett Healthcare, Cooperstown; ~ University of California, Los Angeles, and University of Southern California, Pacific Palisades;d and Sinai Hospital of Baltimore. e This Consensus Panel Conference, "Infection Control: A Focus on MRSA," was held November 17-19, 1995, in Chantilly, Virginia, with the support of a grant from SmithKline Beecham Pharmaceuticals. Reprint requests: Richard E Wenzel, MD, MSc, Medical College of Virginia, Virginia Commonwealth University, PO Box 980663, Richmond, Virginia 23298-0663. Copyright 1998 by the Association for Professionals in Infection Control and Epidemiology, Inc. 0196-6553/98 $5.00 + 0 17/52/85694 The invariable development of resistance to antibiotics by microorganisms is making head- lines in both medical journals and the lay press. The first outbreak of methicillin-resistant Staphylococcus aureus (MRSA) was documented in the United States less than a decade after methicillin was discovered. 1 Within hospitals, the current prevalence of MRSA among all S. aureus isolates probably is 20% to 25% in the United States, 2,3 but it varies between and within com- munities and even within institutions. As a result of a workshop sponsored by the Centers for Disease Control and Prevention (CDC) and aimed at controlling hospital-based antimicro- 102