We report an outbreak of vancomycin-variable vanA+ enterococci (VVE) able to escape phenotypic detection by current guide- lines and demonstrate the molecular mechanisms for in vivo switching into vancomycin resistance and horizontal spread of the vanA cluster. Forty-eight vanA+ Enterococcus faecium isolates and one Enterococcus faecalis isolate were analyzed for clonality with pulsed-field ...