Chapter 15 Microbiology

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Chapter 15 Microbiology
2013-02-10 18:09:05
Streptococcus Enterococcus

Streptococcus and Enterococcus Microbiology
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  1. Streptococcus pneumoniae gram stain morphology
    "Lancet shaped" gram positive diplococci
  2. Streptococcus pneumoniae colony morphology
    • Alpha hemolytic
    • "Oily" (capsulated) to dry (non-capsulated) colonies
  3. Streptococcus pneumoniae identification tools
    • Susceptible to Optichin (>14 mm)
    • Bile Soluble (+)
    • Alpha hemolytic
  4. Streptococcus pneumoniae common disease conditions
    • Pneumonia
    • Otitis media (ear infections)
    • Meningitis
    • Normal flora
  5. Streptococcus pyogenes (Group A) gram stain
    Gram positive cocci (chains)
  6. Group A Strep colony morphology
    Small beta hemolytic colonies
  7. Group A Strep identification tools
    • Bacitracin (S)
    • SXT (R)
    • PYR (+)
    • Beta hemolytic
    • Direct antigen tests (common)
    • Serological test ("Streptozyme", ASO, Anti-Hyaluronidase) can detect antibodies from recent infections
  8. Group A Strep infections
    • "Strep throat"
    • Wounds (cuts, abscesses)
    • Pneumonia
    • Glomerular nephritis (kidney infections)
    • Scarlet fever
    • Rheumatic fever
    • Necrotizing fascitis ("flesh eating bacteria")
  9. Group A Strep treatment
    susceptible to penicillin and erythromycin
  10. Streptolysin O
    • only works under anaerobic conditions
    • -"Stabbing" the agar pushes organisms below the surface and into an anaerobic environment whee Streptolysin O hemolyzes RBCS
    • SSA plate
  11. Streptococcus agalactae (Group B) gram stain
    Gram positive cocci (chains)
  12. Group B Strep colonies
    Beta/Gamma hemolytic colonies (may require 48 hours for beta hemolysis)
  13. Group B Strep infectious conditions
    • Neonatal meningitis and sepsis
    • Puerperal fever
    • Pneumonia
  14. Group B Strep identification tools 
    • Hippurate hydrolysis (+)
    • CAMP (+)
    • Direct antigen tests from female genital sources
  15. Group B Strep treatment
    Susceptible to penicillin and aminoglycosides
  16. Enterococcus  gram stain
    (Lancefield Group D)
    Gram positive cocci (pairs and chains)
  17. Enterococcus Identification tools
    • Catalase may be weakly positive
    • PYR (+)
    • Bile esculin (+)
    • 6.5% NaCl (+)
    • Usually gamma hemolytic
  18. Enterococcus Infectious conditions
    • Normal flora in the GI tract
    • Nosocomial 
    • Opportunistic UTI and abdominal infections
  19. Enterococcus treatment
    Difficult to treat resistant to many antibiotics, including penicillin and vancomycin

    Successful treatment often requires a synergystic relationship between penicillin and vancomycin
  20. Streptococcus bovis (Group D) gram stain
    Gram positive cocci (pairs and chains)
  21. Streptococcus bovis (Group D) identification tools
    • Bile esculin (+)
    • 6.5% NaCl (=)
    • Gamma/Alpha hemolytic
  22. Streptococcus bovis (Group D) infectious conditions
    • Newborn sepsis
    • Endocarditis
  23. Streptococcus bovis (Group D) treatment
    Susceptible to penicillin
  24. Virdans Streptococci ("Strep viridans") gram stain
    Oval, gram positive cocci (chains)
  25. Strep viridans colony
    alpha or gamma hemolytic
  26. Strep viridans treatment
    Susceptible to penicillin
  27. Strep viridans
    Normal flora in the upper respiratory and GI tract
  28. Nutritionally Variant Streptococci (NVS) gram stain 
    Pleomorphic, gram positive cocci
  29. Nutritonally Variant Streptococci (NVS) colonies
    • Very small colonies, require Vitamin B6 or cysteine for growth
    • Growth may only occur near Staph aureus colonies ("satelitism")
  30. NVS treatment 
    Susceptible to penicillin
  31. NVS test
    PYR +
  32. Tests used to ID Streptococcus
    • Hemolysis 
    • Catalase (all Strep neg)
    • Bile Solubility
    • Optichin (P-disk)
    • Bacitracin (A-disk)
    • SXT (SXT-disk)
    • PYR Hydrolysis
    • CAMP Test
    • 6.5% NaCl Broth
    • Bile-Esculin Hydrolysis (BE)
    • Hippurate Hydrolysis
    • Direct Antigen detection of Strep pneumoniae
  33. Special Streptococcus media
    • LIM Broth/Todd-Hewett Broth
    • VRE agar
    • SSA