Effects of antibiotics on nosocomial epidemiology of vancomycin-resistant enterococci

VRE are important nosocomial pathogens that have spread rapidly in several countries since the first isolates were detected approximately 15 years ago. Antibiotic use has been ascribed a crucial role in the dissemination of VRE. However, findings about the effect of antibiotics on the nosocomial epidemiology of VRE have not been consistent across published studies, since multiple biases may have distorted study results (15, 41). For instance, newly detected VRE carriage after antibiotic exposure may have represented either true, nosocomial acquisition of these organisms or expansion of preexisting but previously undetected carriage of VRE in stool (Muto et al., 9th Annu. Sci. SHEA Meet.). Moreover, studies were conducted in different settings, using both case control and cohort study design. Finally, many of the publications addressing this subject had a small sample size, focused on a limited number of antimicrobial agents, or did not adjust for important confounding factors such as length of hospital stay. Nonetheless, several useful findings may be extracted from our systematic review of the literature: (i) only a few studies have systematically examined the effect of antibiotics on the threshold of detection of VRE; (ii) in patients previously free of VRE, intravenous vancomycin use may have a limited role in facilitating new acquisition of VRE, while broad-spectrum cephalosporins or antianaerobic agents may have a more pronounced effect; (iii) many different antibiotic agents may increase VRE density in stool and may thus influence the epidemiology of VRE by increasing the likelihood of transmission; (iv) no antibiotic decolonization regimen has proven to be useful; and (v) the most-promising formulary interventions replaced broad-spectrum cephalosporins with penicillin agents, but more definitive data are needed.