We studied the prevalence and clonality of high-level gentamicin-resistant
enterococci (HLGRE) in a Dutch university hospital. Of 238 enterococcal
strains isolated from blood cultures between 1991 and 1997, 57 were HLGRE.
Genomic analysis of these strains revealed 19 different genotypes, two of
which were encountered more frequently [type A (12/57), type B (23/57)].
The spread of these types largely explained the rise in HLGRE incidence
from 14% in 1991 to 31% in 1997. However, the contribution of unique
strains to the total HLGRE burden also increased from 4% to 16%. We
conclude that both clonal expansion and the emergence of unique HLGRE have
contributed significantly to the increasing incidence of HLGRE.