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 whet her strain definition based on pulsed-field gel electrophoresis (PFGE) is applicable to an endemic setting, Twenty-two PFGE types were ident ified among 455 VRE isolates, One-on-one comparisons of 10 vanA Entero coccus faecium strain types all yielded >10 band differences, Variatio ns among vanA and vanB E. faecium isolates from individual longterm-co lonized (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 an d one with >10 band differences. These data show that VRE isolates wer e genetically closely related or very different; demonstrate that with in individual patients, VRE isolates show Little genetic variation; an d provide empirical evidence that PFGE can be used to study the epidem iology of VRE endemicity.