Treatment of Lancefield Group A Streptococcus (Streptococcus pyogenes) Infections
Penicillin remains the definitive first-line treatment for Group A Streptococcus pharyngitis due to its proven efficacy, safety, narrow spectrum, and low cost, with no documented penicillin resistance ever reported worldwide. 1
First-Line Treatment for Non-Allergic Patients
Oral penicillin V is the gold standard treatment, administered for 10 days to achieve maximal pharyngeal eradication and prevent acute rheumatic fever 1, 2:
- Children: 250 mg twice or three times daily for 10 days 1, 3
- Adolescents and adults: 250 mg four times daily OR 500 mg twice daily for 10 days 1, 3
Amoxicillin is equally effective and often preferred in young children due to better palatability 1:
Intramuscular benzathine penicillin G is preferred when compliance with oral therapy is questionable 1:
Treatment for Penicillin-Allergic Patients
The choice depends on the type of allergic reaction 4, 2:
Non-Immediate/Non-Anaphylactic Penicillin Allergy
First-generation cephalosporins are the preferred alternative 4, 2:
- Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days 4
- Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days 4
Immediate/Anaphylactic Penicillin Allergy
Avoid all beta-lactams due to up to 10% cross-reactivity risk 1, 4. Use:
Clindamycin (preferred for severe allergy):
- 7 mg/kg per dose three times daily (maximum 300 mg/dose) for 10 days 4, 2
- Particularly effective in chronic carriers and recurrent infections 1, 4
- Resistance rate in the United States is approximately 1% 4
Macrolides (acceptable alternatives):
- Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days only 4, 2
- Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg/dose) for 10 days 4
- Erythromycin estolate: 20-40 mg/kg/day divided 2-3 times daily for 10 days 1
Critical caveat: Macrolide resistance varies geographically, with approximately 5-8% resistance in the United States 1, 4. Be aware of local resistance patterns before prescribing 4, 2.
Critical Treatment Duration Requirements
A full 10-day course is mandatory for all antibiotics except azithromycin to achieve maximal pharyngeal eradication and prevent acute rheumatic fever 1, 2. Azithromycin requires only 5 days due to its prolonged tissue half-life 1, 4.
Management of Recurrent Infections
For patients with multiple recurrences 1, 3:
- First recurrence: Retreat with the same antimicrobial used initially 1, 3
- If compliance is questionable: Use intramuscular benzathine penicillin G 1, 3
- For chronic carriers with recurrent episodes: Consider clindamycin or amoxicillin-clavulanate, which achieve higher pharyngeal eradication rates 1, 3
Adjunctive Therapy
- Acetaminophen or NSAIDs for moderate to severe symptoms or high fever 4, 3
- Avoid aspirin in children due to risk of Reye syndrome 4, 3
- Do not use corticosteroids as adjunctive therapy 4
Common Pitfalls to Avoid
Never use shorter courses than recommended (except azithromycin), as this increases the risk of treatment failure and acute rheumatic fever 4, 2. Despite literature suggesting efficacy of 5-day courses for some cephalosporins, these cannot be endorsed due to lack of comprehensive studies 1.
Do not prescribe cephalosporins to patients with immediate hypersensitivity to penicillin, as cross-reactivity occurs in up to 10% of cases 1, 4.
Avoid sulfonamides and tetracyclines entirely, as they have high resistance rates and frequently fail to eradicate even susceptible organisms 1.
Do not routinely retest asymptomatic patients after treatment completion, as this leads to unnecessary retreatment of carriers who are at low risk for complications 1, 2, 3.
Do not routinely test or treat asymptomatic household contacts, as approximately 25% harbor Group A Streptococcus asymptomatically but are at low risk for complications 1, 2.