Emerging incidence of Enterococcus faecium among hospital isolates (1993 to 2002).

Historically, most clinical microbiology laboratories report that 80 to 90% of enterococci are Enterococcus faecalis, whereas E. faecium accounts for 5 to 10% of isolates. At our medical center from 1993 to 2002, we evaluated the percentages of E. faecium among all enterococcal isolates and the percentages of E. faecium isolates that were vancomycin resistant. Over this 10-year period, the percentage of enterococci that were identified as E. faecium increased from 12.7 to 22.2% (P < 0.001) and the proportion of E. faecium that was vancomycin resistant increased from 28.9 to 72.4% (P < 0.001). Both the percentage of E. faecium among the enterococci and the proportion of vancomycin-resistant E. faecium increased significantly over this 10-year period.