USMLE

Strep viridans

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Bacteria - Gram Positive
  1. Staph aureus: Overview
  2. Staph aureus: Presentation
  3. Methicillin-Resistant Staph aureus (MRSA)
  4. Staph saprophyticus
  5. Strep pneumoniae: Overview
  6. Strep pneumoniae: Presentation
  7. Strep viridans
  8. Strep pyogenes: Overview
  9. Strep pyogenes: Presentation
  10. Strep agalactiae
  11. Strep bovis
  12. Enterococcus
  13. Bacillus anthracis
  14. Bacillus cereus
  15. Clostridium tetani
  16. Clostridium perfringens
  17. Clostridium botulinum
  18. Clostridium difficile
  19. Corynebacterium diphtheriae
  20. Listeria monocytogenes
  21. Nocardia
  22. Actinomyces

Strep viridans 

  • Characteristics
    • Gram + cocci
    • Catalase -
      • Determines staph (catalase positive) vs. strep 
    • Alpha-hemolytic
    • Bile-resistant
      • No cell lysis in bile
      • Helps differentiate vs. Strep pneumoniae (bile-sensitive)
    • Optochin-resistant
      • differentiates them from Strep pneumoniae (optochin-sensitive)
  • Presentation
    • normal flora of the oral cavity
      • Transient bacteremia usually occurs after dental work
    • dental caries/cavities
      • Adheres to tooth enamel via biofilm
    • Endocarditis on damaged heart valves
      • most common etiologic agent in subacute bacterial endocarditis (SBE) following dental work
      • Pre-existing valvular abnormality (e.g. rheumatic heart disease, congenital malformations) required since adherence by biofilm requires pre-existing fibrin deposition
      • Contrast to Staph aureus, which binds to normal heart valves 
  • Treatment
    • Antibiotic prophylaxis
      • Administered in patients undergoing dental procedures who are at the highest risk of developing bacterial endocarditis
        • Prosthetic heart valves
        • Prior history of infective endocarditis
        • Unrepaired cyanotic congenital heart disease
        • structurally abnormal valve in a transplanted heart
      • Amoxicillin is treatment of choice