What is the recommended treatment for a patient suspected of having a Group A Streptococcus (GAS) infection, considering their medical history, age, and underlying health conditions?

Treatment of Group A Streptococcal (GAS) Infection

Penicillin or amoxicillin remains the drug of choice for confirmed GAS pharyngitis in non-allergic patients, given at appropriate doses for 10 days to eradicate the organism and prevent acute rheumatic fever. 1

Confirming the Diagnosis

Before initiating antibiotics, GAS infection must be confirmed through microbiological testing, as clinical signs alone cannot reliably distinguish bacterial from viral pharyngitis 1:

• Rapid antigen detection test (RADT) is recommended for office diagnosis, with specificity similar to culture and sensitivity approaching 90% 1
• A positive RADT confirms GAS and justifies antibiotic therapy 1
• A negative RADT in low-risk patients does not require further testing or antibiotics 1
• Throat culture should follow negative RADT only in special circumstances: patients with ARF history, ages 5-25 in high-risk environments, or during outbreaks of rheumatogenic strains 1

First-Line Antibiotic Treatment

Penicillin or amoxicillin is the treatment of choice based on proven efficacy, narrow spectrum, safety, low cost, and absence of documented resistance 1, 2:

• Penicillin V: 50 mg/kg/day in divided doses (maximum 2000 mg/day) for 10 days 1
• Amoxicillin: Often used due to better palatability and compliance 1
• Benzathine penicillin G: Single intramuscular dose (600,000 U for <27 kg; 1,200,000 U for ≥27 kg) when compliance is a concern 1

The 10-day duration is essential to achieve maximal pharyngeal eradication and prevent acute rheumatic fever, even though symptoms typically resolve within 3-4 days 1, 3. Therapy can be safely postponed up to 9 days after symptom onset and still prevent ARF 1.

Treatment for Penicillin-Allergic Patients

The choice of alternative depends on the type of allergic reaction 4, 5:

Non-Immediate (Non-Anaphylactic) Penicillin Allergy

First-generation cephalosporins are preferred with only 0.1% cross-reactivity risk in delayed reactions 5:

• Cephalexin: 20 mg/kg per dose twice daily (maximum 500 mg/dose) for 10 days 5
• Cefadroxil: 30 mg/kg once daily (maximum 1 gram) for 10 days 5

Immediate/Anaphylactic Penicillin Allergy

All beta-lactams must be avoided due to up to 10% cross-reactivity risk 1, 5. Preferred alternatives include:

• Clindamycin (preferred): 7 mg/kg per dose three times daily (maximum 300 mg/dose) for 10 days 4, 5

  • Only ~1% resistance among GAS isolates in the United States 4, 5
  • Superior efficacy with minimal resistance 4
  • Particularly effective in chronic carriers 5

• Azithromycin: 12 mg/kg once daily (maximum 500 mg) for 5 days 5, 6

  • Only macrolide requiring just 5 days due to prolonged tissue half-life 1, 5
  • However, 5-8% macrolide resistance in the United States 4, 5
  • Should be reserved for patients who cannot use clindamycin 5

• Clarithromycin: 7.5 mg/kg per dose twice daily (maximum 250 mg/dose) for 10 days 5

  • Similar resistance concerns as azithromycin 5

Adjunctive Therapy

Symptomatic treatment improves patient comfort but does not replace antibiotics 1:

• Acetaminophen or NSAIDs (ibuprofen) for moderate to severe symptoms or high fever 4, 5
• Avoid aspirin in children due to Reye syndrome risk 5
• Corticosteroids are not recommended 5

Infection Control Measures

For hospitalized patients with GAS infection, strict isolation protocols are required 1:

• Isolate in single room with self-contained toilet and hand basin 1
• Minimum 24 hours of effective antibiotic therapy before ending isolation for most cases 1
• Isolate until culture negative for necrotizing fasciitis, cases with significant discharge, mothers/neonates on maternity units, and burn patients 1
• Strict hand hygiene with soap and water or alcohol hand rub before and after patient contact 1
• Personal protective equipment: disposable gloves and aprons; fluid-repellent surgical masks with visors for procedures producing droplets or during debridement of necrotizing fasciitis 1

Follow-Up and Special Considerations

Routine post-treatment cultures are NOT recommended for asymptomatic patients who completed therapy 1. Most patients with positive cultures after treatment are chronic carriers experiencing intercurrent viral infections 1.

Follow-up testing should be considered only in special circumstances 1:

• Patients with rheumatic fever history
• During outbreaks of ARF, acute glomerulonephritis, or invasive GAS
• Symptoms persist or recur after completing therapy

Chronic carriers generally do not require treatment as they are unlikely to spread GAS or develop complications 1. Treatment may be considered during community outbreaks, with family/personal ARF history, or when excessive family anxiety exists 1.

Critical Pitfalls to Avoid

• Do not prescribe antibiotics without confirming GAS through RADT or culture, as 70-95% of pharyngitis is viral 7
• Do not shorten antibiotic courses below 10 days (except azithromycin's 5-day regimen), as this dramatically increases treatment failure and ARF risk 1, 5
• Do not use cephalosporins in immediate/anaphylactic penicillin allergy due to 10% cross-reactivity 1, 5
• Do not use trimethoprim-sulfamethoxazole for GAS pharyngitis due to high resistance rates 5
• Do not test or treat asymptomatic household contacts routinely 1