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Streptococcal Pharyngitis (Strep Throat)

URI / Outpatient

Source: IDMP View on spectrum chart →
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1. Clinical Syndrome

Acute pharyngitis caused by group A β-hemolytic Streptococcus (Streptococcus pyogenes, GAS) — sudden-onset sore throat, fever, tonsillar exudate, anterior cervical lymphadenopathy, absence of cough/coryza/conjunctivitis (viral features). Treat to prevent rheumatic fever (rare in US; high in resource-limited settings) + suppurative complications (peritonsillar abscess, otitis, sinusitis), and to reduce symptom duration / transmission. Does NOT prevent post-streptococcal glomerulonephritis.

Centor criteria (modified McIsaac): fever >38, tonsillar exudate, anterior cervical lymphadenopathy, absence of cough, age 3–14 (+1) or 15–44 (0) or ≥45 (-1). Score ≥3 → test; score 0–2 → no test, no antibiotics in most cases.

Excludes: viral pharyngitis (most cases — supportive, no antibiotics); infectious mononucleosis (EBV — heterophile / Monospot, tonsillar exudate but generalized lymphadenopathy + splenomegaly, avoid amoxicillin — drug rash); gonococcal pharyngitis (ceftriaxone 500 mg IM); F. necrophorum (Lemierre — adolescent / young adult; antibiotics if severe / persistent); diphtheria (rare; pseudomembrane); HSV gingivostomatitis.

2. Pathogens

Consider the patient: 3–14 y peak; less common in adults but still seen. Outbreaks in families, classrooms, military barracks.

Consider the case: Don't test based on symptoms alone — viral mimics common. Use Centor → RADT (rapid antigen) or throat culture. RADT specificity high (95+%), sensitivity 70–90% (varies). In children + adolescents, confirm RADT-negative with throat culture; in adults, RADT alone is sufficient (low post-strep complication rate). Don't routinely treat GAS carriers (~10–20% of children) — they don't transmit and don't develop rheumatic fever.

Common

Less common

3. Empiric Therapy

TierFirst choiceAlternativesDurationComments
Outpatient
  • 500 mg (adult) / 250 mg (child) · PO BID–TID · PO · 10 days

    **First-line per IDSA 2012.** No documented GAS resistance worldwide.

  • 1000 mg daily or 500 mg BID (adult); 50 mg/kg/day (max 1000 mg) once daily (peds) · PO daily–BID · PO · 10 days

    **Equivalent efficacy, better palatability** (esp. peds suspension). **AVOID if mononucleosis suspected** — drug rash in EBV.

  • 1.2 million units (≥27 kg) or 600,000 units (<27 kg) · single dose · IM

    Single-dose IM benzathine PCN — adherence option (adolescents, transitions of care).

  • 500 mg BID (adult) or 20 mg/kg BID (max 500 mg) peds · PO BID · PO · 10 days

    Mild non-anaphylactic PCN allergy.

  • 12 mg/kg day 1 (max 500 mg), then 6 mg/kg days 2–5 (max 250 mg) · PO daily · PO · 5 days

    True PCN anaphylaxis. **Macrolide resistance in GAS** ~5–15% US (variable by region); confirm if treatment fails.

  • 7 mg/kg TID (max 300 mg) peds; 300 mg TID adult · PO TID · PO · 10 days

    True PCN anaphylaxis. Clindamycin resistance lower than macrolide. Good choice for recurrent GAS (penetrates biofilm, kills carriers).

10 days (5 days OK for azithromycin)**Antibiotic shortens symptoms by ~1 day** and reduces transmission. **Return to school/work after 24 h** of antibiotics + afebrile. **Pain control**: acetaminophen, ibuprofen, throat lozenges, salt-water gargle, +/- single-dose dexamethasone (modest pain reduction). **Do not test of cure** in routine GAS pharyngitis.

4. Directed Therapy

Peritonsillar abscess (quinsy — "hot potato" voice, deviated uvula, severe unilateral pain): drain (ENT — needle aspiration or I&D) + antibiotics (ampicillin-sulbactam IV, clindamycin if PCN-allergic) + admit if severe.

Lemierre syndrome (F. necrophorum septic thrombophlebitis of internal jugular vein in adolescent / young adult with persistent or worsening sore throat → fever → unilateral neck pain → septic pulmonary emboli): admit, IV ampicillin-sulbactam or piperacillin-tazobactam + metronidazole, CT neck + chest, anticoagulation controversial.

Toxic shock syndrome from GAS (streptococcal TSS — necrotizing fasciitis, scarlet fever variants, severe pharyngitis with shock): admit ICU, IV clindamycin (toxin suppression) + penicillin G + IVIG; see necrotizing-fasciitis.

Scarlet fever: GAS pharyngitis with sandpaper-like erythematous rash + circumoral pallor + strawberry tongue — same antibiotics as GAS pharyngitis. Reportable in many jurisdictions.

5. Monitoring

Improvement in fever + sore throat by 24–48 h on antibiotics. Return to school/work after 24 h. No follow-up RADT or culture needed.

Watch for complications: peritonsillar abscess (severe unilateral, voice change), scarlet fever (rash, refer same syndrome), rheumatic fever (delayed weeks; arthritis, carditis, chorea, erythema marginatum, subcutaneous nodules — admit + benzathine PCN secondary prophylaxis), PSGN (1–2 wk delayed; hematuria, edema, HTN — supportive; antibiotics don't prevent).

Toxicity: PCN allergy / rash, GI upset; cephalexin similar; clindamycin C. diff risk.

Pearls

Centor → test, not symptoms alone. Penicillin works — GAS has no documented PCN resistance worldwide. Amoxicillin = penicillin in efficacy, better tasting (peds). Avoid amox if mono suspected. Don't treat asymptomatic carriers. Macrolide resistance is variable — clinda > azithro if PCN-allergic. Antibiotics shorten symptoms ~1 d + reduce transmission + prevent rheumatic fever (rare US). Tonsillectomy for recurrent GAS by Paradise criteria. Return to school 24 h after antibiotic start.

References