The Many Faces of E. Faecium: from Probiotics to Pathogenesis

Enterococcus faecium (E. faecium) represents a controversial species. E. faecium is ubiquitous in nature and adapts easily to diverse environmental conditions due to its ability to acquire and share new genetic elements. E. faecium is also part of the bacterial population in fermented foods contributing in collaboration with other bacterial species to the characteristic flavor and texture of artisanal food products. Finally, E. faecium is also an opportunistic pathogen, which prevented the species to obtain the generally recognized as safe (GRAS) status for use in food and feed production. Furthermore, due to emergence and rapid global spread of vancomycin-resistant E. faecium (VRE) it poses nowadays a serious health treat worldwide. Genetic modelling distinguishes three different “clades” or “lineages” of E. faecium: hospital-associated E. faecium (clade A1), animal-associated (clade A2) and community-associated (clade B). Clade A1 hospital-associated E. faecium are genetically and evolutionarily distinct from community-associated isolates and Clade B E. faecium was recently reassigned to the Enterococcus lactis (E. lactis) group.