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Open Access Highly Accessed Research article

Natural history of colonization with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE): a systematic review

Erica S Shenoy1*, Molly L Paras2, Farzad Noubary3, Rochelle P Walensky4 and David C Hooper5

Author Affiliations

1 Division of Infectious Diseases, Infection Control Unit and Medical Practice Evaluation Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA

2 Division of Infectious Diseases, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA

3 The Institute for Clinical Research and Health Policy Studies, Tufts Medical Center, Tufts Clinical and Translational Science Institute and Tufts University, Boston, MA, USA

4 Divisions of Infectious Diseases, Massachusetts General and Brigham and Women’s Hospital; Medical Practice Evaluation Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA

5 Division of Infectious Diseases, Infection Control Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA

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BMC Infectious Diseases 2014, 14:177  doi:10.1186/1471-2334-14-177

Published: 31 March 2014

Abstract

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, assays used for sampling, and follow-up period. The median duration of total follow-up was 38 weeks for MRSA and 25 weeks for VRE. Based on pooled analyses, the model-estimated median time to clearance was 88 weeks after documented colonization for MRSA-colonized patients and 26 weeks for VRE-colonized patients. In a secondary analysis, clearance rates for MRSA and VRE were compared by restricting the 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.

Conclusions

Few available studies report the natural history of MRSA and VRE colonization. Lack of a consistent definition of clearance, uncertainty regarding the time of initial colonization, variation in frequency of sampling for persistent colonization, assays employed and variation in duration of follow-up are limitations of the existing published literature. The heterogeneity of study characteristics limits interpretation of pooled estimates of time to clearance, however, studies included in this review suggest an increase in documented clearance over time, a result which is sensitive to duration of follow-up.

Keywords:
MRSA; VRE; Colonization; Carrier; Contact precautions