Streptococcus pyogenes (Groups A, B, C, G, F)


>Streptococcus anginosus group (formerly Streptococcus milleri)
     1] Streptococcus intermedius
     2] Streptococcus anginosus
     3] Streptococcus constellatus
>Streptococcus pneumoniae
>Streptobacillus moniliformis
>Streptococcus pyogenes (Groups A, B, C, G, F)led
>Streptococcus agalactiae  (Group B streptococcus)

Streptococcus pyogenes:

  • Spherical, Gram-positive bacterium.
  • Cause of group A streptococcal infections (displays streptococcal group A antigen on its cell wall).
  • S. pyogenes typically produces large zones of beta-hemolysis when cultured on blood agar plates.
  • Streptococci are catalase-negative.
  • Has an incubation period of approximately 1–3 days.
  • It is estimated that there are more than 700 million infections world wide each year and over 650,000 cases of severe, invasive infections that have a mortality rate of 25%.
  • S. pyogenes is the cause of many important human diseases, ranging from mild superficial skin infections to life-threatening systemic diseases.
  • Infections typically begin in the throat or skin. Examples of mild S. pyogenes infections include pharyngitis (“strep throat”) and localized skin infection (“impetigo”).


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Important considerations:  The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions.   Generally, the most common agents/regimens are listed first.    Listed dosages may need to be adjusted for renal dysfunction.

  1. Amoxicillin 500mg orally three times daily or Ampicillin 2 grams IVPB every 4-6 hours
  2. Penicillin G 2-4 million units IV q4-6h or Penicillin VK 500mg orally every 6 hours
  3. Clindamycin  600mg IV every 6 or 8 hours or 300mg orally four times daily 
  4. Ampicillin-sulbactam 1.5 – 3 grams IV q6h
  5. Ceftriaxone 1-2 grams IV q24h
  6. Others


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