Duration of colonization with vancomycin-resistant Enterococcus.

Objective: To determine the duration of colonization with vancomycin-resistant Enterococcus (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.