Schleifer & Kilpper-Bälz 1984
Enterococcus faecium is a Gram-positive, gamma-hemolytic or non-hemolytic bacterium in the genus Enterococcus. It can be commensal (innocuous, coexisting organism) in the gastrointestinal tract of humans and animals, but it may also be pathogenic, causing diseases such as neonatal meningitis or endocarditis.
Pathogenic properties 
This bacterium has developed multi-drug antibiotic resistance and uses colonization and secreted factors in virulence (enzymes capable of breaking down fibrin, protein and carbohydrates to regulate adherence bacteria to inhibit competitive bacteria). The enterococcal surface protein (Esp) allows the bacteria to aggregate and form biofilms. Additional virulence factors include aggregation substance (AS), cytosolin, and gelantinase. AS allows the microbe to bind to target cells and it facilitates the transfer of genetic material between cells.
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 (namely, infections due to central lines, urinary drainage catheters, and ventilators) 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(s) 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.
Enterococcus infections, including VRE infections, cause a range of different symptoms depending on the location of the infection. This includes infections of the bloodstream, urinary tract infections (UTI), and wound infections associated with catheters or surgery. Wound infections associated with catheters and surgery can cause soreness and swelling at wound site, red, warm skin around wounds, and fluid leakage. Urinary tract infections can cause frequent or intense urges to urinate, pain or burning sensations while urinating, fatigue, and lower back or abdominal pain. Bloodstream infections can cause fever, chills, body aches, nausea and vomiting, and diarrhea.
The 22 sequenced Enterococcus faecium genomes:
Tolerance to Alcohol-Based Disinfectants
A study published in 2018 showed multi drug-resistant E. faecium exhibiting tolerance to alcohol-based solutions. The authors speculated about this being an explanation to an increase of E. faecium infections, indicating that alternate methods are required to slow the spread of E. faecium in a hospital setting. The study found that isolates of the bacterium from after 2010 were 10 times more tolerant of the alcohol-based disinfectants than older isolates. However, the isopropanol solutions tested in this study used isopropanol concentrations lower than those used in most hand desinfectants and the authors also stated that hand disinfectants using 70 % isopropanol were effective in full strength even against tolerant strains. However, a mouse gut colonization model of E. faecium transmission showed that alcohol-tolerant E. faecium resisted standard 70% isopropanol surface disinfection, resulting in greater mouse gut colonization compared to alcohol-sensitive E. faecium. This research has led some to question whether it may be possible for microbes to become entirely tolerant of alcohol. 
- Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 294–5. ISBN 0-8385-8529-9.CS1 maint: extra text: authors list (link)
- Willem RJ. "Emerging Infectious Diseases". Centers for Disease Control and Prevention. Retrieved 23 October 2017.
- Mascini EM, Troelstra A, Beitsma M, Blok HE, Jalink KP, Hopmans TE, Fluit AC, Hene RJ, Willems RJ, Verhoef J, Bonten MJ (March 2006). "Genotyping and preemptive isolation to control an outbreak of vancomycin-resistant Enterococcus faecium". Clinical Infectious Diseases. 42 (6): 739–46. doi:10.1086/500322. PMID 16477546.
- Agudelo Higuita NI, Huycke MM (2014). Gilmore MS, Clewell DB, Ike Y, Shankar N (eds.). Enterococci: From Commensals to Leading Causes of Drug Resistant Infection. Boston: Massachusetts Eye and Ear Infirmary. PMID 24649504.
- Gilmore MS, Clewell DB, Ike Y, Shankar N, Agudelo Higuita NI, Huycke MM (February 2014). "Enterococcal Disease, Epidemiology, and Implications for Treatment". In Gilmore MS, Clewell DB, Ike Y (eds.). Enterococci: From Commensals to Leading Causes of Drug Resistant Infection. PMID 24649504.
- "Enterococcal Infections, Vancomycin Resistant" (PDF). Infectious Disease Epidemiology Section Office of Public Health, Louisiana Dept of Health & Hospitals. 8 September 2008.
- Sinel C, Augagneur Y, Sassi M, Bronsard J, Cacaci M, Guérin F, Sanguinetti M, Meignen P, Cattoir V, Felden B (September 2017). "Small RNAs in vancomycin-resistant Enterococcus faecium involved in daptomycin response and resistance". Scientific Reports. 7 (1): 11067. Bibcode:2017NatSR...711067S. doi:10.1038/s41598-017-11265-2. PMC 5593968. PMID 28894187.
- "VRE in Healthcare Settings". United States Centers for Disease Control. Retrieved 23 May 2017.
- Genomes listed are from the "Integrated Microbial Genomes and Microbiomes". United States Department of Energy.
- Pidot, Sacha J.; Gao, Wei; Buultjens, Andrew H.; Monk, Ian R.; Guerillot, Romain; Carter, Glen P.; Lee, Jean Y. H.; Lam, Margaret M. C.; Grayson, M. Lindsay (2018-08-01). "Increasing tolerance of hospital Enterococcus faecium to handwash alcohols". Science Translational Medicine. 10 (452): eaar6115. doi:10.1126/scitranslmed.aar6115. ISSN 1946-6234. PMID 30068573.
- "Some Bacteria Are Becoming 'More Tolerant' Of Hand Sanitizers, Study Finds". NPR.org. Retrieved 2018-08-06.
- Cai Y, Wang R, Liang B, Bai N, Liu Y (March 2011). "Systematic review and meta-analysis of the effectiveness and safety of tigecycline for treatment of infectious disease". Antimicrobial Agents and Chemotherapy. 55 (3): 1162–72. doi:10.1128/AAC.01402-10. PMC 3067123. PMID 21173186.
- Chewning JH (July 2011). "Vancomycin-resistant Enterococcus faecium bacteremia successfully treated with high-dose ampicillin-sulbactam in a pediatric patient after hematopoietic stem cell transplantation". Journal of Pediatric Hematology/Oncology. 33 (5): 401. doi:10.1097/MPH.0b013e31820db7eb. PMID 21602724.