>Enterococcus faecium (E. faecium)
- Enterococcus: Two species are common commensal organisms in the intestines of humans: E. faecalis (90-95%) and E. faecium (5-10%).
- Gram-positive cocci that often occur in pairs (diplococci) or short chains.
- Nonmotile, facultatively anaerobic microbe.
- Formerly classified as part of the Group D Streptococcus system
- Non-spore forming, but tolerant to a wide range of environmental conditions.
- Can cause life-threatening infections especially in a hospital setting (high levels of resistance).
- Important clinical infections caused by Enterococcus include urinary tract infections, bacteremia, bacterial endocarditis, diverticulitis, and meningitis.
- Enterococcus species have a high level of intrinsic antibiotic resistance. Some enterococci are intrinsically resistant to β-lactam-based antibiotics (penicillins, cephalosporins, carbapenems), as well as many aminoglycosides.
- Enterococci are relatively impermeable to aminoglycosides. Combination therapy with a cell wall-active agent (e.g. beta-lactam) is required in order to raise the permeability of the cell so that an adequate intracellular aminoglycoside concentration can be achieved while reducing the risk of toxicity.
- Vancomycin-resistant Enterococcus (VRE): particularly virulent strains of Enterococcus that are resistant to vancomycin. Treatment options for vancomycin-resistant E. faecalis include linezolid and daptomycin, although ampicillin is preferred if the bacteria are susceptible. Quinupristin/dalfopristin can be used to treat Enterococcus faecium but not E. faecalis.