Antimicrobial pressure and the emergence and spread of multiresistant enterococci.

Multiresistant enterococci persist as important pathogens, particularly in US tertiary care hospitals. The emergence of vancomycin and ampicillin resistance in clinical Enterococcus faecium strains and the ascension of this species as an important nosocomial pathogen are among the more remarkable developments in the past decade. This emergence and spread is due to both the failure to adhere to well-established infection control measures and the persistent selective antibiotic pressure exerted in tertiary care institutions. Accumulating data specifically implicate the use of extended-spectrum cephalosporins and drugs with potent activity against anaerobic bacteria in the spread of vancomycin-resistant enterococci (VRE). These antibiotics appear to exert different effects on the initial establishment or the persistence of high levels of VRE colonization. Successful strategies to control the spread of multiresistant enterococci will require a more detailed understanding of the specific impacts of antimicrobial pressures as well as renewed commitment to adherence to well-established infection control measures.