Duration of Colonization with Vancomycin-ResistantEnterococcus

Abstract

Objective:To determine the duration of colonization with vancomycin-resistantEnterococcus(VRE) and the adequacy of 3 consecutive negative cultures to determine clearance.Design:Retrospective cohort study.Setting:A university hospital.Population:Patients identified by perirectal cultures as VRE carriers who had follow-up cultures.Methods:Follow-up perirectal cultures were collected in inpatient and outpatient settings, at least 1 week apart, when patients were not receiving antibiotics with activity against VRE. The likelihood of culture positivity was analyzed given prior culture results and time from the initial positive culture.Results:A total of 116 patients colonized with VRE had 423 follow-up cultures, a mean of 204 days (range, 4 to 709 days) after their initial isolate. The first follow-up culture, collected a mean of 125 days after the initial positive isolate, was negative in 64%. After 1 negative follow-up culture, the next one was negative in 92% of the patients. After 2 negative cultures, 95% remained culture-negative. After 3 sequential negative cultures, 35 (95%) of 37 patients remained culture-negative. As the interval between the initial and the follow-up isolates increased, the probability that a subsequent culture would be positive decreased (P< .001, chi square for trend). Prolonged hospitalization, intensive care, and antibiotic use each decreased the likelihood of clearing VRE.Conclusion:These data support the Centers for Disease Control and Prevention criterion of 3 sequential negative cultures, at least 1 week apart, to remove patients from VRE isolation. Nevertheless, this may reflect a decrease in the quantity of VRE to an undetectable level and these patients should be observed for relapse, especially when re-treated with antibiotics.