Enterococcus faecium
Enterococcus faecium is a Gram-positive, gamma-hemolytic or non-hemolytic bacterium in the genus Enterococcus. It can be commensal in the gastrointestinal tract of humans and animals, but it may also be pathogenic, causing diseases such as neonatal meningitis or endocarditis.
Vancomycin-resistant E. faecium is often referred to as VRE.
Pathogenic properties
This bacterium has developed multi-drug antibiotic resistance and uses colonization and secreted factors in virulence. The enterococcal surface protein allows the bacteria to aggregate and form biofilms. Additional virulence factors include aggregation substance, cytosolin, and gelatinase. AS allows the microbe to bind to target cells and it facilitates the transfer of genetic material between cells.By producing the enterocins A, B, and P, Enterococcus faecium can combat pathogenic gut microbes, such as Escherichia coli, reducing gastrointestinal disease in hosts. As an alternative to adding antibiotics to livestock feed, which risks antimicrobial resistance, E. faecium Strain NCIMB 10415 is being used as a probiotic in animal feed. However, the constant exposure to high levels of this microbe result in immunosuppression by reducing expression of IL-8, IL-10, and CD86, predisposing livestock to severe Salmonella infections.
Metabolism
E. faecium exhibits a metabolically flexible and heterogeneous profile, particularly in clinical settings such as catheter-associated urinary tract colonization. A 2025 study of urinary isolates from intensive care unit patients revealed that E. faecium consistently metabolizes lactose and L-arabinose, while showing little to no ability to utilize melezitose or inositol. E. faecium isolates often varied and adapted their substrate usage even within the same patient, indicating high intra-host metabolic diversity.Vancomycin-resistant ''Enterococci'' (VRE)
Enterococcus faecium has been a leading cause of multi-drug resistant enterococcal infections over Enterococcus faecalis in the United States. Approximately 40% of medical intensive care units reportedly found that the majority, respectively 80% and 90.4%, of device-associated infections were due to vancomycin- and ampicillin-resistant E. faecium.The rapid increase of VRE has made it difficult for physicians to fight infections caused by E. faecium since not many antimicrobial solutions are available. In the United States infections by VRE occurs more frequently.
Persons infected or colonized with VRE are more likely to transmit the organism. Transmission depends primarily on which body site harbor the bacteria, whether the body fluids are excreted and how frequently health care providers touch these body sites. Patients infected or colonized with VRE may be cared for in any patient care setting with minimal risk of transmission to other patients provided appropriate infection control measures are taken.
A genome-wide E. faecium sRNA study suggested that some sRNAs are linked to the antibiotic resistance and stress response.
Patients with bloodstream infections caused by E. faecium have a higher mortality rate compared to those caused by Enterococcus faecalis.