Morphology: Gram-positive cocci in pairs/short chains, vancomycin-resistant (vanA / vanB).
VREEnterococcusGramPosOther
Typical drugs
- #1Linezolid— Bacteriostatic — limit in endocarditis.
- #2Daptomycin— High-dose for serious infections.
Empiric therapy when resistant
Linezolid 600 mg IV/PO q12h. Daptomycin 8–10 mg/kg/day for bacteremia/endocarditis. Combination therapy often considered for endocarditis.
Resistance mechanisms
Target alteration
vanA / vanB modify peptidoglycan terminus from D-Ala-D-Ala to D-Ala-D-Lac, preventing vancomycin binding
Example: VRE
Resistance notes
Most VRE in US are E. faecium. E. faecalis is usually still vancomycin-susceptible.
Pearls
Risk factors: prior vancomycin, long hospital stay, immunocompromise. Don't reflexively cover VRE — confirm if isolated.