Vancomycin-resistant enterococcus (VRE) carriage and infection in intensive care units

From July, 1997, through December, 2001, patients who were admitted to intensive care units (ICUs) were enrolled in the study of vancomycin resistance enterococcus (VRE) colonization. Among 4,538 patients admitted to the ICUs, 363 (8.0%) patients were found to have positive culture of VRE at the day of admission to the ICUs and 453 (10.0%) of patients were negative to the first day of admission but became colonized with VRE during the stay in ICU. Among 816 patients, 9 (1.1%) with VRE isolated from sterile sites were selected for further analysis. Pulsed-field gel electrophoresis (PFGE) revealed a total of four PFGE banding patterns in the colonized and infected Enterococcus faecium isolates. Six of nine 9 were found to have an identical PFGE type Ia, suggesting the circulation of an endemic strain. All of these type Ia isolates also contained two potential virulence genes, the esp and hly genes and were first identified in Asia. After the further typing of 540 isolates that were randomly selected from each month, the endemic strain was not identified before the first patient was colonized and infected with this strain in November, 1998, but was isolated from other ICU patients during each month thereafter throughout the remainder of the study period. Although colonization of VRE is the first step toward infection, a low infection rate was observed, except in patients with prolonged hospitalization and severe illness. Use of the isolation room and reminders regarding hand hygiene failed to prevent the circulation of endemic strain. Thus, the SHEA guideline (Muto et al., Infect. Control Hosp. Epidemiol. 2003;24:362-386) for preventing nosocomial transmission of VRE should be enforced.