Clonal diversity of vancomycin-resistant enterococci from an outbreak in a tertiary care university hospital

Background: Enterococci have become important nosocomial pathogens and now account for approximately 12% of nosocomial infections. Enterococci can be transferred from patient to patient and from health care personnel to patient. We investigated the clonal diversity of vancomycin-resistant enterococci (VRE) causing an outbreak of infections and attempted to determine the patterns of spread of these bacteria in a university hospital. Methods: Ribotyping was used to examine the clonal diversity of 50 VRE isolates, including 23 from wounds, 14 from urine, 8 from blood, 3 from the rectum, 1 from drainage, and 1 from the cornea. Results: Nine patients were infected with Enterococcus faecalis, 10 with Enterococcus faecium, 3 with both E faecalis and E faecium, and 1 with Enterococcus avium. The results suggest that the sources of the VRE infections included endogenous strains and strains acquired by transmission from attending staff or from the environment. Three patients were infected by both nosocomial and endogenous strains. Conclusions: These data suggest that the collection and analysis of several isolates from repeated specimens is necessary to obtain a fuller understanding of the epidemiology and population structure of antibiotic-resistant enterococci.