SPREAD OF VANCOMYCIN-RESISTANT ENTEROCOCCI - WHY DID IT HAPPEN IN THEUNITED-STATES

The question of why vancomycin-resistant enterococci (VRE) became epid emic in the United States can be answered on at least three basic leve ls: (1) molecular and genetic, (2) factors affecting host-microbe inte ractions, and (3) epidemiological. This article will address the epide miological issues and seek to defend the assertion that, once VRE had evolved, its spread throughout hospitals in the United States was all but assured. Nosocomial VRE outbreaks were reported first in the mid- and late-1980s. Since that time, scientific reports of VRE have increa sed over 20-fold. Among hospitals participating in the National Nosoco mial Infection Surveillance System from 1989 to 1997, the percentage o f enterococci reported as resistant to vancomycin increased from 0.4% to 23.2% in intensive-care settings and from 0.3% to 15.4% in non-inte nsive-care settings. Factors leading to the spread of VRE in US hospit als include (1) antimicrobial pressure, (2) sub-optimal clinical labor atory recognition and reporting, (3) unrecognized ''silent'' carriage and prolonged fecal carriage, (4) environmental contamination and surv ival, (5) intrahospital and interhospital transfer of colonized patien ts, (6) introduction of unrecognized carriers from community settings such as nursing homes, and (7) inadequate compliance with hand washing and barrier precautions. Guidelines developed by the Centers for Dise ase Control and Prevention's Hospital Infection Control Practices Advi sory Committee address each of these factors. The impact of these guid elines on the spread of VRE within individual institutions has been va riable, and the overall impact of the guidelines nationally is unknown .