396. The Natural History of Colonization with Methicillin-Resistant Staphylococcus Aureus (MRSA) and Vancomycin-Resistant Enterococcus (VRE): A Systematic Review
Session: Poster Abstract Session: MRSA, MSSA, Enterococci
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C

Background: No published systematic reviews have assessed the natural history of colonization with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococcus (VRE). Time to clearance of colonization has important implications for patient care and infection control policy.

Methods: We performed parallel searches in OVID Medline for studies that reported the time to documented clearance of MRSA and VRE colonization in the absence of treatment, published between January 1990 and July 2012.

Results: For MRSA, we screened 982 articles, identified 16 eligible studies (13 observational studies and 3 randomized controlled trials), for a total of 1,804 non-duplicated subjects. For VRE, we screened 284 articles, identified 13 eligible studies (12 observational studies and 1 randomized controlled trial), for a total of 1,936 non-duplicated subjects. Studies reported varying definitions of clearance of colonization; no study reported time of initial colonization. Studies varied in the frequency of sampling and follow-up period. The reported median duration of follow-up was 38 weeks for MRSA and 25 weeks for VRE. Based on pooled analyses, the median time to clearance was 88 weeks for MRSA-colonized patients (Fig 1A) and 26 weeks for VRE-colonized patients (Fig 1B). In a secondary analysis, clearance rates for MRSA and VRE were compared by restricting duration of follow-up for the MRSA studies to the maximum observed time point for VRE studies (43 weeks). With this restriction, the model-fitted median time to documented clearance for MRSA would occur at 41 weeks after documented colonization, demonstrating the sensitivity of the pooled estimate to length of study follow up.

Conclusion: Few available studies report the natural history of MRSA and VRE colonization. Those included in this review suggest an increase in documented clearance over time, a result which is sensitive to the duration of follow up. Lack of a consistent definition of clearance, uncertainty regarding the time of initial colonization, variation in frequency of sampling for persistent colonization, and variation in duration of follow up are limitations of the existing published literature.

Erica S. Shenoy, MD, PhD, Department of Medicine, Massachusetts General Hospital, Boston, MA; Medicine, Harvard Medical School, Boston, MA; Infection Control Unit, Massachusetts General Hospital, Boston, MA, Molly Paras, MD, Medicine, Massachusetts General Hospital, Boston, MA, Farzad Noubary, PhD, The Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, Boston, MA, Rochelle Walensky, MD, MPH, FIDSA, General Medicine Division, Massachusetts General Hospital, Boston, MA and David Hooper, MD, Massachusetts General Hospital, Boston, MA


E. S. Shenoy, None

M. Paras, None

F. Noubary, None

R. Walensky, None

D. Hooper, None

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