Enterococcus faecalis - Bacterial strain, organism, antimicrobial therapy,
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Enterococcus faecalis

Background:

Enterococci
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>Enterococcus faecalis
>Enterococcus faecium (E. faecium)


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 beta-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:

Important considerations:  The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions.   Generally, the most common agents/regimens are listed first.  Listed dosages may need to be adjusted for renal dysfunction.
  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. 


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