Enterococcus faecalis

Enterococcus faecalis

Background:

Enterococcus faecalis:

• 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 -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.

Therapy:

1. (Penicillin G or Ampicillin) +/- (gentamicin or streptomycin)  [see comments above]
2. Ampicillin-sulbactam 1.5 – 3 gm IV q6h
3. Vancomycin 1 gram  ivpb q12h (patient-specific dosing required)  +/- (gentamicin or streptomycin)
4. UTI:  VRE:  Nitrofurantoin 50-100mg q6h or Fosfomycin 3 gm orally x 1 dose

VRE: See comments above.

1. Linezolid 600 mg orally or IV q 12h
2. Daptomycin  4 – 6 mg/kg IV once daily.