Structure and transfer of the vanA cluster in vanA-positive, vancomycin-susceptible Enterococcus faecium, and its revertant mutant.

Of 18 vanA-positive vancomycin-susceptible Enterococcus faecium isolates, vanRS in the vanA cluster was detected in all isolates, while vanHAX was detected in only 2 isolates. Following exposure to glycopeptides, 22.2% of vancomycin-susceptible E. faecium (VSE) converted into vancomycin-resistant E. faecium. The vanA cluster of the revertant mutant was transferred to the VSE isolates.