Molecular and clinical epidemiology of vancomycin-resistant Enterococcus faecalis.

OBJECTIVES With the recent emergence of vancomycin-resistant (VR) Staphylococcus aureus, subsequent to the suggested transfer of the vanA resistance gene from Enterococcus faecalis, we sought to determine risk factors for acquisition of VR E. faecalis and to evaluate the molecular epidemiology of this less-prevalent and less-studied species of VR enterococcus. METHODS We compared clinical isolates of VR E. faecalis from 71 patients, collected over 12 years in a large community teaching hospital, with isolates from 126 patients with vancomycin-susceptible E. faecalis. RESULTS Risk factors for VR E. faecalis acquisition by multivariate analysis were nursing home residence (P = 0.0005), haemodialysis (P = 0.009), decubitus ulcers (P = 0.03) and receipt of parenteral vancomycin (P = 0.0002). Twenty-one percent of VR E. faecalis demonstrated vanA and 79% vanB resistance. The number of VanA isolates increased over time. Molecular analysis showed vanA or vanB in multiple PFGE groups. CONCLUSIONS The results of this study suggest gene dissemination among some isolates and intra-hospital spread of other isolates. The risk factors identified clearly suggest that VR E. faecalis is a nosocomial pathogen and should be considered in infection control practices. Further surveillance of VR E. faecalis is warranted, due to the potential spread of vancomycin resistance among enterococci and staphylococci.