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 vancomyc in-resistant enterococci (VRE) in intensive care units (ICUs) during a non- outbreak period by examining prevalence, risk factors for colonization, fre quency of acquisition, and molecular strain types. Design: A prospective cohort design was followed. Consecutive patient admis sions to 2 surgical ICUs at a tertiary care hospital were enrolled. The mai n outcome measures were results of serial surveillance cultures screened fo r VRE. Results: Of 290 patients enrolled, 35 (12%) had colonization with VRE on ad mission. The VRE colonization or infection had been previously detected by clinical cultures in only 4 of these patients. Using logistic regression, V RE colonization at the time of ICU admission was associated with second- an d 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 p rior ICU stay (OR = 9.6, P = .002), and a history of solid-organ transplant ation (OR = 3.8, P = .021). Eleven (12.8%) of 78 patients with follow-up cu ltures acquired VRE. By pulsed-field gel electrophoresis, 2 strains predomi nated, 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 surgi cal ICU acquired VRE prior to surgical ICU entry. Exposure to second- and t hird-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.