Streptococcus pyogenes (Groups A, B, C, G, F)
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Background:
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Streptococci
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>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)
>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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Therapy:
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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.
- Amoxicillin 500mg orally three times daily or Ampicillin 2 grams IVPB every 4-6 hours
- Penicillin G 2-4 million units IV q4-6h or Penicillin VK 500mg orally every 6 hours
- Clindamycin 600mg IV every 6 or 8 hours or 300mg orally four times daily
- Ampicillin-sulbactam 1.5 – 3 grams IV q6h
- Ceftriaxone 1-2 grams IV q24h
- Others
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