Variant esp gene as a marker of a distinct genetic lineage of vancomycin-resistant Enterococcus faecium spreading in hospitals

In the USA, vancomycin-resistant Enterococcus faecium (VREF) is endemic in hospitals, despite lack of carriage among healthy Individuals. In Europe, h owever, hospital outbreaks are rare, but VREF carriage among healthy indivi duals and livestock is common. We used amplified fragment-length polymorphi sm analysis to genotype 120 VREF isolates associated with hospital outbreak s and 45 nonepidemic isolates hom the USA, Europe, and Australia. We also l ooked for the esp virulence gene in these isolates and in 98 VREF from anim als. A specific E faecium subpopulation genetically distinct from non-epide mic VREF isolates was found to be the cause of the hospital epidemics in al l three continents. This subpopulation contained a variant of the esp gene that was absent in all nonepidemic and animal isolates. Identification of t he variant esp gene will be important in guiding infection-control strategi es, and the Esp protein could be a new target for antibacterial therapy.