Enterococcus species

Background

Microbiology

• Facultative anaerobic, non-spore-forming, alpha- or gamma-hemolytic, catalase-negative, Gram-positive cocci"cocci" is not in the list (coccus, bacillus, coccobacillus, diplococcus, spirochete, curved, pleomorphic, yeast, mold) of allowed values for the "Shape" property.
• Grows on bile esculin agar
• PYR positive
• Most are Lancefield group D
• Commensal gut flora
• Increasing antibiotic resistance

Species

• E. faecalis
  • More common (90-95%)
  • More commonly genitourinary source
  • More susceptible to antibiotics
• E. faecium
  • Less common (5-10%)
  • More commonly gastrointestinal source
  • Less susceptible to antibiotics
  • Most common VRE
• E. gallinarum
• E. casseliflavus

Vacomycin Resistance

• Vancomycin binds to d-Ala-d-Ala pentapeptids, interfering with cell wall synthesis
• VanA: most common. Mutation to d-Ala-d-Lac, leading to high resistance to glycopeptides.
• VanB: more common in E. faecium in Australia
• VanC: chromosomal resistance on E. gallinarum and E. casseliflavus

Management

VRE

• Daptomycin, doxycycline, linezolid, tedizolid, oritavancin, quinupristin-dalfopristin (for E. faecium)