Vancomycin-resistant enterococci in intensive care units: High frequency of stool carriage during a non-outbreak period

Background: We aimed to define the epidemiological associations of vancomycin-resistant enterococci (VRE) in intensive care units (ICUs) during a non-outbreak period by examining prevalence, risk factors for colonization, frequency of acquisition, and molecular strain types. Design: A prospective cohort design was followed. Consecutive patient admissions to 2 surgical ICUs at a tertiary care hospital were enrolled. The main outcome measures were results of serial surveillance cultures screened for VRE. Results: Of 290 patients enrolled, 35 (12%) had colonization with VRE on admission. The VRE colonization or infection had been previously detected by clinical cultures in only 4 of these patients. Using logistic regression, VRE colonization at the time of ICU admission was associated with second- and third-generation cephalosporins (odds ratio [OR] = 6.0, P < .0001), length of stay prior to surgical ICU admission (OR = 1.06, P = .01) greater than 1 prior ICU stay (OR = 9.6, P = .002), and a history of solid-organ transplantation (OR = 3.8, P = .021). Eleven (12.8%) of 78 patients with follow-up cultures acquired VRE. By pulsed-field gel electrophoresis, 2 strains predominated, one of which was associated with an overt outbreak on a non-ICU ward near the end of the study period. Conclusions: Colonization was common and usually not recognized by clinical culture. Most patients who had colonization with VRE and were on the surgical ICU acquired VRE prior to surgical ICU entry. Exposure to second- and third-generation cephalosporins, but not vancomycin, was an independent risk factor for colonization. Prospective surveillance of hospitalized patients may yield useful insights about the dissemination of nosocomial VRE beyond what is appreciated by clinical cultures alone.