What is the recommended antibiotic treatment for streptococcal (strep) infections?

Recommended Antibiotic Treatment for Streptococcal Infections

Penicillin remains the treatment of choice for streptococcal pharyngitis due to its proven efficacy, safety, narrow spectrum, and low cost. 1

First-Line Treatment Options

For Patients Without Penicillin Allergy

Oral penicillin V or amoxicillin for 10 days is the standard treatment. 1

• Penicillin V dosing:

  • Children: 250 mg twice or three times daily for 10 days 1
  • Adolescents and adults: 250 mg four times daily OR 500 mg twice daily for 10 days 1

• Amoxicillin dosing (often preferred in children due to better taste):

  • 50 mg/kg once daily (maximum 1,000 mg) for 10 days 1
  • Alternative: 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 1

• Intramuscular benzathine penicillin G (for patients unlikely to complete oral therapy):

  • <60 lb (27 kg): 600,000 units as a single dose 1
  • ≥60 lb: 1,200,000 units as a single dose 1

The 10-day duration is essential to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever. 1 Shortening the course by even a few days results in appreciable increases in treatment failure rates. 2

For Patients With Penicillin Allergy

The type of penicillin allergy determines which alternative antibiotic is safe to use. 2

Non-Immediate (Non-Anaphylactic) Penicillin Allergy

First-generation cephalosporins are the preferred first-line alternatives. 1, 2

• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg per dose) for 10 days 1
• Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days 1

These have strong, high-quality evidence supporting their efficacy with only 0.1% cross-reactivity risk in patients with non-severe, delayed penicillin reactions. 2

Immediate/Anaphylactic Penicillin Allergy

Avoid all beta-lactam antibiotics (including cephalosporins) due to up to 10% cross-reactivity risk. 1, 2 Immediate reactions include anaphylaxis, angioedema, respiratory distress, or urticaria occurring within 1 hour of penicillin administration. 2

Clindamycin is the preferred alternative for immediate penicillin allergy:

• 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days 1, 2
• Approximately 1% resistance rate among Group A Streptococcus in the United States 2
• Strong, moderate-quality evidence for efficacy 1

Macrolide alternatives (with resistance concerns):

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 2
• Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg per dose) for 10 days 1

Macrolide resistance among Group A Streptococcus ranges from 5-8% in the United States, though this varies geographically and temporally. 1, 2 Azithromycin requires only 5 days due to its prolonged tissue half-life, unlike other antibiotics that require the full 10 days. 2

Necrotizing Fasciitis and Streptococcal Toxic Shock Syndrome

For severe Group A streptococcal infections (necrotizing fasciitis or toxic shock syndrome), use clindamycin PLUS penicillin. 1

• Clindamycin: 600-900 mg every 8 hours IV (adults) 1
• Penicillin: 2-4 million units every 4-6 hours IV (adults) 1

The rationale for clindamycin is based on in vitro studies demonstrating toxin suppression and modulation of cytokine production, with superior efficacy versus penicillin in animal studies. 1 Penicillin should be added because only 0.5% of macrolide-resistant Group A streptococci in the United States are also clindamycin resistant. 1

Chronic Streptococcal Carriers

Chronic carriers generally do not require treatment, as they are unlikely to spread infection or develop complications. 1, 2 However, if treatment is indicated (e.g., during outbreaks, family history of rheumatic fever), use:

• Clindamycin: 20-30 mg/kg per day in three doses (maximum 300 mg per dose) for 10 days 1
• Amoxicillin/clavulanate: 40 mg amoxicillin/kg per day in three doses (maximum 2,000 mg amoxicillin per day) for 10 days 1

These regimens have been shown to yield high rates of pharyngeal eradication of streptococci in chronic carriers. 1

Critical Pitfalls to Avoid

• Never shorten the antibiotic course below 10 days (except azithromycin's 5-day regimen) - this increases treatment failure rates and risk of acute rheumatic fever 1, 2
• Do not use cephalosporins in patients with immediate/anaphylactic penicillin reactions - up to 10% cross-reactivity risk 1, 2
• Do not prescribe azithromycin or clarithromycin without considering local resistance patterns - macrolide resistance varies geographically and can lead to treatment failure 1, 2
• Do not use sulfonamides or tetracyclines - higher resistance rates and frequent failure to eradicate even susceptible organisms 3
• Do not routinely perform post-treatment throat cultures in asymptomatic patients who have completed therapy 1

Adjunctive Therapy

• Acetaminophen or NSAIDs (such as ibuprofen) should be considered for moderate to severe symptoms or high fever 1, 2
• Avoid aspirin in children due to risk of Reye syndrome 1, 2
• Corticosteroids are not recommended as adjunctive therapy 1, 2