Whole-genome sequencing surveillance of vancomycin-resistant Enterococcus faecium (VRE) detects hospital outbreaks and identifies the postanesthesia care unit as a transmission locus.

Abstract

Objective: Vancomycin-resistant enterococci (VRE) can cause serious healthcare-associated infections. Patients can become colonized and infected through contact with healthcare workers, hospital surfaces, equipment, and other patients. We evaluated the utility of broadly applied whole-genome sequencing (WGS) surveillance of vancomycin-resistant Enterococcus faecium (VREfm) for detection of hospital-based transmission.

Design: Retrospective genomic and epidemiologic analysis of clinical VREfm isolates.

Setting: Brigham and Women's Hospital, an 800-bed tertiary care center in Boston, MA, USA.

Methods: VREfm was isolated from patient screening and diagnostic specimens. We sequenced the genomes of 156 VREfm isolates, 12 at the request of infection control and 144 as a convenience sample, and used single nucleotide polymorphism (SNP) differences to assess relatedness. For isolate pairs separated by 15 or fewer SNPs by two orthogonal comparison methods, we mapped epidemiologic connections to identify putative transmission clusters.

Results: We found evidence for 16 putative transmission clusters comprising between two and four isolates each and involving 41/156 isolates (26.3%). Our analysis discovered 14 clusters that were missed by traditional surveillance methods and additional members of two clusters that were detected by traditional methods. Patients in four transmission clusters were linked only by exposure to the postanesthesia care unit.

Conclusions: We show that WGS surveillance for VREfm can support infection control investigations and detect transmission events missed by routine surveillance methods. We identify the postanesthesia care unit as a locus for VREfm transmission, which demonstrates how WGS surveillance could inform targeted interventions to prevent the spread of VREfm.