What is the recommended diagnosis and treatment for a patient exposed to streptococcal infection with symptoms of a sore throat?

Diagnosis and Treatment for Streptococcal Exposure with Sore Throat

Do not test or treat asymptomatic household contacts, even when a family member has confirmed strep throat—testing and empiric treatment of contacts is not recommended. 1

Assessment of the Symptomatic Patient

Your patient has symptoms (sore throat) and known streptococcal exposure, which increases clinical suspicion. However, diagnosis still requires laboratory confirmation before initiating antibiotics. 1

Clinical Evaluation Using Centor Criteria

Assess the following clinical features to determine testing strategy: 1

• Fever (temperature >38°C)
• Tonsillar exudate (white patches or pus on tonsils)
• Tender anterior cervical lymphadenopathy
• Absence of cough (cough suggests viral etiology)

Score interpretation: 1

• 0-2 criteria: Low probability of strep—antibiotics should not be used
• 3-4 criteria: Higher probability—proceed with rapid antigen detection test (RADT)

Diagnostic Testing Algorithm

For patients with 3-4 Centor criteria or high clinical suspicion: 1

1. Perform RADT first (sensitivity 80-90%, specificity ≥95%) 1, 2

2. If RADT is positive: Begin antibiotic treatment immediately 1

3. If RADT is negative in children/adolescents: Confirm with throat culture before withholding antibiotics (culture remains gold standard with 90-95% sensitivity) 1, 3

4. If RADT is negative in adults: No backup culture needed—the negative result is sufficient to rule out strep pharyngitis 1, 4

Treatment When Strep is Confirmed

First-Line Antibiotic Therapy

Penicillin V is the drug of choice for all non-allergic patients due to narrow spectrum, proven efficacy, safety, and low cost—no penicillin resistance has ever been documented in Group A Streptococcus. 1, 5

Dosing regimens: 1

• Children: Penicillin V 250 mg orally twice or three times daily for 10 days
• Adolescents/Adults: Penicillin V 250 mg three to four times daily OR 500 mg twice daily for 10 days
• Alternative: Benzathine penicillin G 1.2 million units intramuscularly as single dose (preferred for patients unlikely to complete 10-day oral course) 1

Amoxicillin is often substituted for young children due to better taste acceptance, with equivalent efficacy. 1

Critical Treatment Duration

A full 10-day course is essential to achieve maximal pharyngeal eradication and prevent acute rheumatic fever—shortening the course by even a few days significantly increases treatment failure rates. 1, 5 Treatment can be safely initiated up to 9 days after symptom onset and still prevent rheumatic fever. 1, 4

For Penicillin-Allergic Patients

Determine the type of allergic reaction first: 5

Non-immediate/non-anaphylactic penicillin allergy (delayed rash):

• First-generation cephalosporins are preferred (cross-reactivity risk only 0.1%) 5
• Cephalexin 20 mg/kg/dose twice daily (max 500 mg/dose) for 10 days 5
• Cefadroxil 30 mg/kg once daily (max 1 gram) for 10 days 5

Immediate/anaphylactic penicillin allergy (hives, angioedema, bronchospasm within 1 hour):

• Avoid all beta-lactams including cephalosporins (up to 10% cross-reactivity risk) 1, 5
• Clindamycin is preferred: 7 mg/kg/dose three times daily (max 300 mg/dose) for 10 days (only ~1% resistance in US) 5
• Azithromycin alternative: 12 mg/kg once daily (max 500 mg) for 5 days only (5-8% macrolide resistance in US) 5
• Clarithromycin alternative: 7.5 mg/kg/dose twice daily (max 250 mg/dose) for 10 days 5

Symptomatic Management

Provide analgesics for all patients regardless of antibiotic use: 5, 4

• Ibuprofen or acetaminophen for pain and fever control 1, 5
• Avoid aspirin in children due to Reye syndrome risk 5
• Do not use corticosteroids as adjunctive therapy 5

Critical Pitfalls to Avoid

Do not treat based on clinical symptoms alone—even experienced physicians cannot reliably diagnose strep pharyngitis without laboratory confirmation, and up to 70% of sore throat patients receive unnecessary antibiotics. 1, 4

Do not test or treat asymptomatic household contacts—approximately 25% of household members may carry Group A Streptococcus asymptomatically, but prophylactic treatment is not indicated and does not reduce subsequent infection rates. 1, 4

Do not perform routine post-treatment cultures—follow-up testing is not recommended for asymptomatic patients who completed appropriate therapy, as positive results cannot distinguish carriers from active infection. 1, 4

Do not prescribe broad-spectrum antibiotics—penicillin's narrow spectrum is a major advantage, and broader agents unnecessarily increase selection pressure for resistant organisms. 1, 5