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Enterococci (group D streptococci)

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Topic updated on 08/12/17 10:13pm

Introduction
  • Classification
    • Bacteria
      • Gram-positive cocci
        • Enterococci
          • Enterococcus faecalis
          • Enterococcus faecium
  • LanCefield group D includes
    • enterococci
    • nonenterococcal group D streptococci
      • Lancefield grouping is based on differences in the C carbohydrate on the bacterial cell wall
  • Pathogenesis
    • transmission
      • endogenous
    • reservoir
      • normal flora of colon
      • urethra
      • female genital tract
    • molecular biology
      • GI or GU tract damage during surgery leads to bacteremia
      • presence of previously damaged heart valves leads to endocarditis
  • Etymology
    • entero = intestine
    • faecalis = feces
    • strepto = twisted (chains)
    • coccus = berry
Diseases
  • Endocarditis (subacute)
    • damaged heart valves predispose to infection
    • especially in elderly
  • UTI
  • Biliary tract infections
Laboratory
  • Evaluation
    • hydrolyzes esculin in 40% bile and 6.5% NaCl
      • bile esculin agar turns black
      • ability to grow in NaCl
        • growth in NaCl differentiates from nonenterococcal group D (Strep bovis)
          • Enterococci are hardier!
        • both Strep bovis and Enterococci can grow in bile
    • variable hemolysis
    • cocci in chains
    • PYR (pyrrolidonyl arylamidase) positive
    • catalase negative
  • Diagnosis
    • culture on blood agar
    • antibiotic sensitivities
Treatment
  • Vancomycin
  • VRE (vancomycin-resistant enterococci) are an important cause of nosocomial infection
    • treat VRE with linezolid and streptogramins (e.g. quinupristin/dalfopristin)
  • Penicillin G resistant
    • all strains exhibit some drug resistance
  • Prophylactic antibiotics before GI/GU surgery in high-risk patients


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