A sustained hospital outbreak of vancomycin-resistant Enterococcus faecium bacteremia due to emergence of vanB E. faecium sequence type 203.
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, coinciding with the appearance of a vanB VREfm ST203, the rate of VRE bacteremia has increased exponentially. Although we found no difference in antiseptic susceptibility or presence of genes encoding putative virulence determinants (esp(Efm), hyl(Efm), and fms genes), comparative genomics revealed almost 500 kb of unique sequence when an ST17 and an ST203 VREfm isolate were compared, suggesting that other genomic factors are responsible for the apparent success of E. faecium.


CONCLUSIONS
The application of multilocus sequence typing has uncovered the emergence of an epidemic clone of E. faecium ST203 that appears to have acquired the vanB locus and has caused a sustained outbreak of VRE bacteremia.
Johnson
Paul D R
PD
Department of Infectious Diseases and Microbiology, Austin Health, Monash University, Melbourne, Victoria, Australia.
Ballard
Susan A
SA
Grabsch
Elizabeth A
EA
Stinear
Timothy P
TP
Seemann
Torsten
T
Young
Heather L
HL
Grayson
M Lindsay
ML
Howden
Benjamin P
BP
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001315:Australia / Q000453:epidemiology; D016470:Bacteremia / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D001426:Bacterial Proteins / Q000235:genetics*; D015373:Bacterial Typing Techniques; D021821:Communicable Diseases, Emerging / Q000382:microbiology; D003428:Cross Infection / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D016984:Enterococcus faecium / Q000145:classification / Q000187:drug effects / Q000235:genetics*; D023281:Genomics; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology*; D006801:Humans; D015994:Incidence; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D010802:Phylogeny; D013845:Thienamycins / Q000627:therapeutic use; D014640:Vancomycin / Q000627:therapeutic use; D020713:Vancomycin Resistance / Q000235:genetics*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D013845:Thienamycins; C079913:VanB protein, Enterococcus; D014640:Vancomycin; D000077731:Meropenem