Molecular epidemiology of vancomycin-resistant Enterococcus faecium in a large urban hospital over a 5-year period

To investigate the dissemination of vancomycin-resistant Enterococcus faeci um (VREF) in a 728-bed tertiary-care hospital, all clinical VREF isolates r ecovered from June 1992 to June 1997 were typed by pulsed-field gel electro phoresis, and the transfer histories of the patients were documented. A tot al of 413 VREF isolates from urine (52%), wounds (16%), blood (11%), cathet er tips (6%), and other sites (15%) were studied. VREF specimens mostly cam e from patients on wards (66%) but 34% came from patients in an intensive c are unit, The number of VREF isolates progressively increased over time, wi th higher rates of isolation during the winter months and lower rates in th e late summer months. Four distinct banding patterns were detected by pulse d-field gel electrophoresis among 316 samples (76%). Strain A (122 samples; 30%) appeared in June 1992 as the first VREF strain and was found until De cember 1994 throughout the entire hospital. Type B (92 samples; 22%) was in itially detected in January 1994 and disappeared in November 1996, Strain C (10 samples; 2%) was limited to late 1996 and early 1997, Strain D (92 sam ples; 22%) showed two major peaks during March 1996 to August 1996 and Janu ary 1997 to February 1997, Unrelated strains (97 samples; 24%) appeared 1 y ear after the appearance of the first VREF isolate, and the numbers increas ed slightly over the gears. Nosocomial acquisition (i,e,, no known detectio n prior to admission and first isolation from cultures performed with sampl es retrieved greater than or equal to 2 days after hospitalization) was fou nd for 316 (91%) of 347 patients. Despite the implementation of Centers for Disease Control and Prevention guidelines, the proportion of related strai ns and high number of nosocomial cases of infection indicate a high transmi ssion rate inside the hospital. The results imply an urgent need for string ent enforcement of more effective infection control measures.