Resistance Mechanisms, Epidemiology, and Approaches to Screening for Vancomycin-Resistant Enterococcus in the Health Care Setting

Abstract

bInfections attributable to vancomycin-resistant Enterococcus (VRE) strains have become increasingly prevalent over the past decade. Prompt identification of colonized patients combined with effective multifaceted infection control practices can reduce the transmission of VRE and aid in the prevention of hospital-acquired infections (HAIs). Increasingly, the clinical microbiology laboratory is being asked to support infection control efforts through the early identification of potential patient or environmental reservoirs. This review discusses the factors that contribute to the rise of VRE as an important health care-associated pathogen, the utility of laboratory screening and various infection control strategies, and the available laboratory methods to identify VRE in clinical specimens. Hospital-acquired infections (HAIs) are a serious threat for patient care and carry a significant cost to hospitals, since treatment of these infections is no longer reimbursable. In addition, regulations requiring hospitals to report HAIs creates further pressure to reduce incidence rates. Screening patients at admission for methicillin-resistant Staphylococcus aureus (MRSA) has been a successful approach in reducing MRSA HAIs in some health care systems and may be a successful strategy for controlling other health care-associated pathogens, including Clostridium difficile, carbapenem-resistant Enterobacteriaceae (CRE), and vancomycin-resistant Enterococcus (VRE) (1). However, there is debate about the optimal approach to screening and infection control, which may differ between pathogens of interest.Members of the genus Enterococcus are well-documented pathogens associated with various clinical manifestations, including bacteremia, infective endocarditis, intra-abdominal and pelvic infections, urinary tract infections, and, in rare cases, central nervous system infections (2-4). Infection with vancomycin-resistant Enterococcus is associated with an increased mortality rate, illustrated by a 2.5-fold increase in mortality for patients suffering from VRE bacteremia (5). Vancomycin resistance in Enterococcus spp. has been increasing in prevalence since it was first encountered in 1986 (6, 7). Currently, 30% of Enterococcus species isolates from the United States are vancomycin resistant, and infection with these organisms causes an estimated 1,300 deaths each year (8). The majority of VRE are associated with the species E. faecium (77%) and E. faecalis (9%), with the remaining 14% of isolates representing species less frequently implicated in serious infections, including E. gallinarum, E. casseliflavus, E. avium, and E. raffinosus (8).The optimal approach to reducing VRE infections is multifactorial, requiring antimicrobial stewardship to reduce the selection of VRE in colonized patients, appropriate infection control practices to reduce transmission, and reliable sensitive laboratory methods for the detection of VRE in a timely manner. ANTIMICROBIAL RESISTANCE MECHANISMS AND APPROACHES TO THERAPYUnderstanding the mechanism be...

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