A sustained hospital outbreak of vancomycin-resistant Enterococcus faecium bacteremia due to emergence of vanB E. faecium sequence type 203

Abstract

Background. A significant increase in the rate of vancomycin-resistant Enterococcus faecium (VREfm) bacteremia at our health service, despite improved infection control, prompted us to investigate the cause. Methods. E. faecium bacteremia (including VREfm) over a 12-year period (1998-2009) was investigated using multilocus sequence typing, antibiotic and antiseptic susceptibility profiles, optical mapping, and whole genome sequencing of historical and recent isolates. Results. For 10 years, the rate of bacteremia due to vanB VREfm remained stable and sequence type (ST) 17 was predominant. In 2005, ST203 vancomycin-susceptible E. faecium first appeared at our institution, and from March 2007,..