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- Enterococci are facultative anaerobic, Gram-positive bacteria in short chains; may grow under extreme conditions, i.e., 6.5% NaCl, pH 9.6, temperature range from 10-45°C, and in the presence of bile salts.
- Significant component of normal colonic flora, present in oropharyngeal and vaginal secretions
- Found in soil, water, food
- Adheres to extracellular matrix proteins and urinary tract epithelia
- Produces biofilms
- Exploits opportunity to proliferate once antibiotic-susceptible organisms are eradicated
- Species-specific antimicrobial resistance differences, e.g., high-level β-lactam resistance is increasing in E. faecium, but uncommon in E. faecalis.
- Intrinsically resistant to many β-lactams (e.g., cephalosporins) due to inner cell wall penicillin-binding proteins.
- Resistant to TMP/SMX as organism uses exogenous folate to overcome anti-folate synthesis mechanism.
- Relatively impermeable to aminoglycosides (AG), addition of a cell-wall agent may allow bactericidal effect at ribosomal target.
- Ribosomal mutation and decreased aminoglycoside transport confer high-level AG resistance.
- Some gentamicin-resistant strains may remain susceptible to streptomycin.
- Vancomycin resistant enterococci (VRE): occurs E. faecium >>> E. faecalis.