Natural History of Colonization with Vancoimycin-Resistant Enterococcus faecium

Abstract

Objective: To determine the incidence, duration, and genetic diversity of colonization with vancomycin-resistant Enterococcus faecium (VREF). Setting: Oncology unit of a 650-bed university hospital. Methods: Surveillance perianal swab cultures were performed on admission and weekly. The molecular relatedness of VREF isolates was determined by pulsed-field gel electrophoresis and by the hybridization pattern of the vanA resistance determinant. Results: During 8 months of surveillance, the VREF colonization rate was 16.6 Patients per 1,000 patient-hospital days, which was 10.6 times greater than the VREF infection rate. Eighty-six Patients with VREF colonization were identified. Colonization persisted for at least 7 weeks in the majority of Patients. Of 36 colonized Patients discharged from the hospital and then readmitted, an average of $2\frac{1}{2}$ weeks later, 22 (61%) Patients still were colonized with VREF. Of the 14 Patients who were VREF-negative at readmission, only three Patients remained culture-negative throughout hospitalizations. PFGE demonstrated that colonization with the same VREF isolate may persist for at least 1 year, and Patients may be colonized with more than one strain of VREF. Conclusion: VREF colonization is at least 10-fold more prevalent than infection among oncology Patients. Colonization often persists throughout lengthy hospitalizations and may continue for long periods following hospitalization.