What are the recommended antibiotics (Abx) for streptococcal infections?

Recommended Antibiotics for Streptococcal Infections

Penicillin remains the treatment of choice for Group A streptococcal pharyngitis due to its proven efficacy, safety, narrow spectrum of activity, and low cost. 1, 2

First-Line Treatment Options

Oral Options:

• Penicillin V:

  • Children: 250 mg 2-3 times daily for 10 days
  • Adolescents/adults: 250 mg 4 times daily or 500 mg twice daily for 10 days 1, 2

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

  • 50 mg/kg once daily (maximum 1000 mg) for 10 days, OR
  • 25 mg/kg twice daily (maximum 500 mg per dose) for 10 days 2, 3

Parenteral Option:

• Benzathine Penicillin G (intramuscular):
  • Patients <27 kg: 600,000 units as a single dose
  • Patients ≥27 kg: 1,200,000 units as a single dose
  • Particularly useful for patients unlikely to complete a full 10-day oral course 1, 2

For Penicillin-Allergic Patients:

Non-Anaphylactic Allergy:

• First-generation cephalosporins (if no immediate hypersensitivity to β-lactams):
  • Cephalexin: 20 mg/kg twice daily (max 500 mg per dose) for 10 days 2
  • Cefadroxil: 30 mg/kg once daily (max 1 g) for 10 days 2

Anaphylactic Allergy:

• Erythromycin:
  • Estolate: 20-40 mg/kg/day in 2-3 divided doses for 10 days
  • Ethyl succinate: 40 mg/kg/day in 2-3 divided doses for 10 days 1, 4
• Clindamycin: 7 mg/kg three times daily for 10 days (max 300 mg per dose) 2
• Azithromycin: 12 mg/kg once daily (max 500 mg) for 5 days 2, 5
  • Note: Caution with macrolides due to potential resistance (up to 5% of GAS in the US) 2

Important Clinical Considerations:

1. Duration of Treatment:

   • A full 10-day course is strongly recommended for most antibiotics to achieve maximal pharyngeal eradication and prevent complications such as acute rheumatic fever 1, 2
   • Azithromycin is the exception with a 5-day course 2, 6

2. Dosing Frequency:

   • Twice-daily dosing of penicillin is as effective as more frequent dosing regimens 7
   • Once-daily dosing of penicillin is associated with decreased efficacy and should not be used 7
   • Amoxicillin can be effectively administered once daily 2, 7

3. Treatment Failures:

   • Penicillin failure rates have increased over time, now reported to be approximately 30% 8
   • Common causes include poor compliance with the 10-day regimen, reexposure to infected individuals, and penicillin tolerance 8

4. Post-Treatment Considerations:

   • Patients are considered non-contagious after 24 hours of antibiotic therapy 2
   • Clinical response typically occurs within 24-48 hours of starting treatment 2
   • Follow-up cultures are not routinely recommended if symptoms resolve 2

Special Situations:

• Carriers: GAS carriers do not ordinarily require identification or antimicrobial therapy, as they are unlikely to spread GAS pharyngitis and are at minimal risk for developing complications 2

• Persistent Symptoms: If symptoms persist or worsen after 5 days of appropriate treatment, consider:

  • Non-compliance with the prescribed regimen
  • Penicillin treatment failure
  • New infection with GAS
  • Viral pharyngitis in a streptococcal carrier 2

Remember that despite newer antibiotics being available, penicillin has never encountered documented resistance from GAS, making it the cornerstone of treatment for streptococcal pharyngitis 1, 2.