Molecular characterization of vancomycin-resistant enterococci from clinical and surveillance specimens

OBJECTIVE. To compare the molecular characteristics of infection-derived ( ID) isolates and intestinal colonization-derived ( ICD) isolates of vancomycin-resistant enterococci ( VRE) recovered from hospitalized patients. DESIGN. A 12-month prospective cohort study. SETTING. A 1,000-bed teaching facility. METHODS. From January through December 2004, a total of 30 pairs of vanA-containing enterococcal isolates were collected from patients admitted to a teaching hospital in South Korea. Each pair comprised an ID and an ICD VRE isolate from the same patient. All VRE isolates were investigated on the basis of SmaI-restricted pulsed-field gel electrophoresis ( PFGE) pattern, Tn1546 type, and presence of the esp gene, including A and C repeat number variation. RESULTS. Members of 19 pairs ( 63%) of VRE isolates were genetically indistinguishable from each other. The 11 patients for whom the molecular characteristics of the ID isolates differed from those of the ICD isolates had longer durations of hospitalization and intensive care unit ( ICU) stay, compared with the other 19 patients. CONCLUSIONS. These findings suggest the longer durations of hospitalization and ICU stay may be possible risk factors for colonization with multiple clones of VRE.