A 28-year-old woman presents to the emergency department with a 2-day history of severe sore throat, fever (39.5°C), and difficulty swallowing. On examination, she has exudative pharyngitis with enlarged tonsils, palatal petechiae, and tender anterior cervical lymphadenopathy. A rapid antigen detection test (RADT) for group A Streptococcus is positive. She has no history of penicillin allergy. What is the most appropriate immediate antibiotic therapy?

Explanation

## Diagnosis and Treatment Rationale **Key Point:** Acute pharyngitis caused by *Streptococcus pyogenes* (Group A Streptococcus) is treated with penicillin V as first-line therapy, given orally for 10 days to eradicate the organism and prevent suppurative and non-suppurative sequelae. ### Clinical Presentation Recognition The patient presents with classic acute streptococcal pharyngitis: - Exudative pharyngitis with enlarged tonsils - Fever and severe pharyngeal pain - Cervical lymphadenopathy (tender, anterior) - Palatal petechiae (characteristic finding) - Positive RADT confirms Group A Streptococcus ### Antibiotic Selection | Feature | Penicillin V | Cephalexin | Azithromycin | Clindamycin | |---------|--------------|-----------|--------------|-------------| | **First-line agent** | Yes | Alternative | Macrolide (resistance emerging) | Alternative | | **Duration** | 10 days | 10 days | 3–5 days (suboptimal) | 10 days | | **Mechanism** | β-lactam, cell wall | β-lactam, cell wall | Protein synthesis inhibitor | Protein synthesis inhibitor | | **Resistance rate** | <1% | <1% | 5–15% (increasing) | <1% | | **Indication** | Standard therapy | Penicillin allergy (non-severe) | Macrolide allergy | Penicillin allergy (severe) | **High-Yield:** Penicillin V (oral) or Penicillin G (IM) remain the gold standard for Group A Streptococcal pharyngitis. The 10-day course is essential to prevent acute rheumatic fever (ARF) and post-streptococcal glomerulonephritis (PSGN). **Clinical Pearl:** A positive RADT is highly specific (>95%) for GAS pharyngitis and does not require throat culture confirmation before starting treatment. Treatment should be initiated immediately to reduce symptom duration and prevent sequelae. ### Why 10 Days? Shorter courses (3–5 days) are inadequate for prevention of non-suppurative sequelae. The 10-day regimen achieves sustained bactericidal levels in the throat and tonsillar tissue. **Mnemonic: GAS Pharyngitis Treatment — "PEN for 10"** - **P**enicillin V (oral) or Penicillin G (IM) - **E**radication of organism - **N**on-suppurative sequelae prevention - **10** days of therapy [cite:Harrison 21e Ch 297]