Genomic Insights to Control the Emergence of Vancomycin-Resistant

P.D.R.J. and T.P.S. are joint senior authors. ABSTRACT Nosocomial outbreaks of vancomycin-resistant Enterococcus faecium (VREfm) are thought to occur by transmission of VREfm between patients, predicting that infection control interventions will limit cross-transmission. Despite implementa-tion of such strategies, the incidence of VREfm infections continues to rise. We aimed to use genomics to better understand the epidemiology of E. faeciumwithin a large hospital and investigate the reasons for failure of infection control strategies. Whole-genome sequencing was performed on 61 E. faecium (36 VREfm) isolates, predominately from blood cultures collected at a sin-gle hospital between 1998 and 2009, and on five vanB-positive anaerobic commensal bacteria isolated from human feces. Phylog-enomic analysis and precise mapping of the vanB gene, which contains the Tn1549 transposon, showed that at least 18 of the 36 VREfm isolates had acquired the transposon via independent insertion events, indicating de novo generation of VREfm rathe