Role of environmental contamination in the transmission of vancomycin-resistant enterococci.

Abstract

The acquisition and spread of bacterial resistance to commonly used antibiotics is an ongoing problem in the 1990s.1 Important nosocomial pathogens with an increasing incidence or newly acquired resistance include oxacillin-resistant Staphylococcus aureus, enteric gram-negative bacilli producing extended-spectrum p-lactamase, and vancomycin-resistant Enterococcus species (VRE). Reports of VRE began to appear in the mid-1980s in Europe and are now an important problem in an evergrowing number of hospitals in the United States. Data accumulated via the National Nosocomial Infection Surveillance (NNIS) system of the Centers for Disease Control and Prevention (CDC) revealed that VRE increased 35-fold among all nosocomial isolates of enterococci (0.3% to 10.4%) between 1989 and 1995.2 By 1994 and 1995, 41% of all NNIS hospitals reported at least one nosocomial enterococcal infection. A recent report notes that attributable mortality is approximately 40%.3 Because of the importance of VRE as a nosocomial pathogen, the Hospital Infection Control Practices Advisory Committee (HICPAC) of the CDC has published guidelines for preventing nosocomial transmission.4 Among the important scientific questions regarding nosocomially acquired VRE are the following. First, do patients colonized or infected with VRE contaminate their environment? Second, what is the role of surface contamination in the transmission of VRE? Third, is surface contamination linked to the transmission of other nosocomial pathogens? Finally, what scientifically based policies can infection control professionals adopt to prevent or reduce nosocomial transmission of these pathogens? Several investigators have studied the frequency of environmental contamination found in the rooms of patients with VRE."11 Cultures of the surface environment yielded VRE in 7% to 37% of samples (Table). These investigations also produced several other important findings. Boyce et al reported that environmental contamination was more widespread in the rooms of patients with diarrhea6 (Table). In a later study, Boyce et al reported that the disposable gowns of nurses who cared for a patient with copious diarrhea also were contaminated with VRE.8 Montecalvo et al reported that 8% of cultures taken after terminal cleaning still yielded VRE.7 Molecular analysis of VRE strains has demonstrated both multiple circulating strains9,1112 and outbreaks due to a single strain.6,8,12,13 In some cases, isolates obtained from the environment were identical to the epidemic strain causing infection.6'8 However, in these outbreaks, it often has been difficult to determine whether cross-transmission occurred due to contaminated common equipment (eg, stethoscopes), acquisition of transient hand carriage by