Molecular epidemiology of vancomycin-resistant Enterococcus faecium bloodstream infections among patients with neutropenia over a 6-year period in South Korea.
Over a 6-year period (March 2000-February 2006), there were 60 vancomycin-resistant Enterococcus faecium (VREF) bloodstream infections (BSIs) in a hematology unit, accounting for 83.3% of all VREF BSIs in the hospital. We investigated 49 VREF isolates causing BSIs in patients with neutropenia to understand the molecular epidemiology at this unit. All isolates had the vanA genotype. Pulsed-field gel electrophoresis typing revealed high clonal diversity (23 types with nine clusters comprising 35 isolates) and 1 predominant type, type A (14/49, 28.6%), persisted at this unit throughout the study period, suggesting the clonal spread of this endemic strain by cross-contamination. Tn1546 types were less heterogeneous, with five main Tn1546 types, two of which (types I and IV) accounted for 67.4% of isolates. This indicates that in addition to clonal spread, the horizontal transfer of Tn1546 played a major role in the nosocomial dissemination of vancomycin resistance. The genetic diversity of VREF increased over time, implying an increasing influx of new strains into the unit and genetic changes, possibly attributable to the horizontal transfer of diverse Tn1546 types. Despite such diversity, all the isolates belonged to clonal complex 17, which is the epidemic clone worldwide, enriched with the esp (35/49, 71.4%) and hyl (24/49, 48.9%) virulence genes. This hospital-adapted clone has become endemic and is well suited to causing BSIs in patients with neutropenia in this unit.
Division of Infectious Diseases, Department of Internal Medicine, The Catholic University of Korea, College of Medicine, Seoul, Korea.
Sun Hee
SH
Park
Chulmin
C
Park
Su-Mi
SM
Choi
Dong-Gun
DG
Lee
Si-Hyun
SH
Kim
Jae-Cheol
JC
Kwon
Ji-Hyun
JH
Byun
Jung-Hyun
JH
Choi
Jin-Hong
JH
Yoo
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016470:Bacteremia / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D003428:Cross Infection / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D016984:Enterococcus faecium / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology / Q000379:methods; D058889:Molecular Typing / Q000379:methods; D009503:Neutropenia / Q000382:microbiology; D056910:Republic of Korea / Q000453:epidemiology; D020713:Vancomycin Resistance
D000900:Anti-Bacterial Agents