What is the recommended treatment for a patient with streptococcal (strep) infection who is allergic to penicillin (PCN) products?

Treatment of Streptococcal Infection in Penicillin-Allergic Patients

For patients with streptococcal infection who are allergic to penicillin products, clindamycin is the recommended first-line treatment for those with high risk of anaphylaxis, while cefazolin is preferred for those without history of severe allergic reactions.

Assessment of Penicillin Allergy Severity

The approach to treatment depends on the severity of the penicillin allergy:

1. High-risk for anaphylaxis (history of anaphylaxis, angioedema, respiratory distress, or urticaria following penicillin administration):

   • Avoid penicillins, ampicillin, and cephalosporins 1
   • Susceptibility testing should be performed when possible

2. Low-risk for anaphylaxis (no history of severe reactions):

   • Cefazolin is the preferred agent 1

Treatment Recommendations

First-line options:

• For high-risk penicillin allergy patients:

  • Clindamycin: 300-450 mg orally three times daily for 10 days for adults 2, 3
  • For children: 8-16 mg/kg/day divided into three or four equal doses for serious infections; 16-20 mg/kg/day for more severe infections 3

• For low-risk penicillin allergy patients:

  • Cefazolin: 2g IV initial dose, then 1g IV every 8 hours until delivery (for GBS prophylaxis) 1
  • For non-IV settings, other first-generation cephalosporins can be used 4

Alternative options:

• Azithromycin: 500 mg once on day 1, followed by 250 mg once daily for 4 days 5, 6

  • For children: 12 mg/kg once daily (max 500 mg) for 5 days 2
  • Note: Due to increasing resistance, susceptibility testing should be performed when patients are treated with azithromycin 5

• Vancomycin: Consider for severe infections or when susceptibility testing shows resistance to clindamycin 1, 2

Important Considerations

1. Duration of therapy:

   • For streptococcal pharyngitis/tonsillitis, treatment should continue for at least 10 days to prevent rheumatic fever 3, 7
   • Exception: Azithromycin can be given for 5 days due to its prolonged tissue half-life 8

2. Resistance concerns:

   • Some strains of Group A Streptococcus are resistant to azithromycin, making susceptibility testing important 5
   • Penicillin treatment failures have increased over time (up to approximately 30%) 9

3. Follow-up:

   • Patients with Group A Streptococcal pharyngitis are considered non-contagious after 24 hours of effective antibiotic therapy 2
   • Follow-up throat cultures are not routinely indicated for asymptomatic patients who have completed appropriate therapy 2

Pitfalls to Avoid

1. Do not use tetracyclines (doxycycline, minocycline) in children under 8 years of age 2

2. Do not discontinue antibiotic therapy early, even if symptoms improve, to prevent complications like rheumatic fever 7

3. Monitor for significant diarrhea during clindamycin therapy, as this may indicate C. difficile infection and require discontinuation of the antibiotic 3

4. Do not rely on azithromycin to treat syphilis, which may coexist with streptococcal infections in some patients 5

5. Be aware that erythromycin resistance is often associated with clindamycin resistance, which may require testing for inducible clindamycin resistance 1

By following these evidence-based recommendations, clinicians can effectively treat streptococcal infections in penicillin-allergic patients while minimizing the risk of adverse reactions and treatment failure.