Last Bacteria Standing: VREfm Persistence in the Hospitalized Gut

Enterococci are gram-positive, gastrointestinal (GI) tract commensal bacteria that have recently evolved into multidrug-resistant nosocomial pathogens. Enterococci are intrinsically hardy, meaning that they can thrive in challenging environments and outlast other commensal bacteria. Further adaptations enable enterococci to dominate the GI tracts of hospitalized patients, and this domination precedes invasive infection and facilitates transmission to other patients. A recent study by Boumasmoud et al. used whole genome sequencing (WGS) to characterize 69 vancomycin-resistant Enterococcus faecium (VREfm) isolates collected from a Swiss hospital. WGS uncovered a clone that was repeatedly sampled from dozens of patients over multiple years. This persistent clone accumulated mutations as well as a novel linear plasmid, which together likely increased its persistence in the GI tracts of infected patients. This study is one of several recent examples that highlight the genetic plasticity of VREfm as it adapts to the hospitalized gut and becomes a leading nosocomial pathogen.