Stability of vancomycin-resistant enterococcal genotypes isolated from long-term-colonized patients

Genotypic variation and stability of isolates of vancomycin-resistant enterococci (VRE) were studied to determine genetic diversity and whether strain definition based on pulsed-field gel electrophoresis (PFGE) is applicable to an endemic setting, Twenty-two PFGE types were identified among 455 VRE isolates, One-on-one comparisons of 10 vanA Enterococcus faecium strain types all yielded >10 band differences, Variations among vanA and vanB E. faecium isolates from individual longterm-colonized (4-160 days) patients yielded <3 band differences for >85% of comparisons, Comparison of all strains without grouping by vancomycin resistance types yielded two peaks of band differences: one with <3 and one with >10 band differences. These data show that VRE isolates were genetically closely related or very different; demonstrate that within individual patients, VRE isolates show Little genetic variation; and provide empirical evidence that PFGE can be used to study the epidemiology of VRE endemicity.