Role of Environmental Contamination as a Risk Factor for Acquisition of Vancomycin-Resistant Enterococci in Patients Treated in a Medical Intensive Care Unit

Abstract

SINCE THEIR FIRST appearance in 1988, vancomycin-resistant enterococci (VRE) have become endemic in many hospitals throughout the United States. According to data from the National Nosocomial Infections Surveillance System, by the end of 1999 about 25% of all enterococci involved in nosocomial infections were resistant to vancomycin hydrochloride.¹ For patients admitted to the intensive care unit (ICU), the prevalence of resistance in the first 5 months of 1999 was 47% higher than during the period from 1994 to 1998.² Patients with hematologic malignancies, transplant recipients, and the critically ill are at particular risk for colonization and subsequent infection with VRE.³ Because in the United States there are no reservoirs of vancomycin-resistant Enterococcus faecium or Enterococcus faecalis other than colonized patients,^4-7 and because resistance to glycopeptides cannot be selected by antibiotics from a previously susceptible bacterial population,⁸ each instance of colonization or infection with these organisms represents an episode of horizontal transmission, many of which occur in the hospital setting. Once colonized, patients become long-term carriers,⁹ so in a given facility or unit the endemic prevalence of VRE is related to the admission rate of previously colonized patients.¹⁰ This basal rate will eventually be increased by new cases resulting from cross-transmission through the hands of health care workers and, possibly, other items.