EENT · PANCE / PANRE

Group A Streptococcal Pharyngitis

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

GAS bacterial pharyngitis — diagnose with RADT/culture and treat with penicillin to prevent rheumatic fever.

Also known as: GAS pharyngitis, strep throat, group A strep, streptococcal pharyngitis

Overview

Acute pharyngitis caused by Streptococcus pyogenes (group A beta-hemolytic Streptococcus, GAS). Distinguished from far more common viral pharyngitis by clinical features supported by rapid antigen detection test (RADT) and/or throat culture.

Epidemiology

GAS causes 15-30% of pharyngitis in children and 5-15% in adults. Most common in children 5-15 years. Peak in late winter/early spring. Spread by respiratory droplets; incubation 2-5 days. Asymptomatic carriage 5-20% in school-age children.

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Question 1EENTEasy
A 9-year-old girl presents with a 2-day history of sore throat, fever, and painful swallowing, without cough or rhinorrhea. Exam shows tonsillar exudates, tender anterior cervical lymphadenopathy, and a temperature of 38.8 C. A rapid streptococcal antigen test is positive. She weighs 30 kg and has no drug allergies. Which of the following is the most appropriate first-line antibiotic?
  • AAzithromycin
  • BTrimethoprim-sulfamethoxazole
  • CAmoxicillin
  • DCiprofloxacin
Reveal answer & full explanation
Correct answer: C — Amoxicillin
  • AAzithromycin
  • BTrimethoprim-sulfamethoxazole
  • CAmoxicillin✓
  • DCiprofloxacin

Why amoxicillin is correct

  • This is group A streptococcal (GAS) pharyngitis, confirmed by a positive rapid antigen test in a child meeting Centor/McIsaac criteria (fever, tonsillar exudates, tender anterior cervical adenopathy, absence of cough)
  • Group A Streptococcus has never developed penicillin resistance, so a narrow-spectrum penicillin is first-line
  • In non-allergic children, amoxicillin (50 mg/kg once daily, max 1000 mg, for 10 days) is the IDSA-preferred regimen because once-daily dosing and palatable suspension improve adherence
  • Adequate treatment shortens symptoms, reduces transmission, lowers the risk of suppurative complications such as peritonsillar abscess, and prevents acute rheumatic fever

Why the others are wrong

  • Azithromycin — reserved for severe penicillin allergy; rising GAS macrolide resistance limits it as a routine first choice
  • Trimethoprim-sulfamethoxazole — does not reliably eradicate GAS and does not prevent rheumatic fever, so it is inappropriate for pharyngitis
  • Ciprofloxacin — a fluoroquinolone with poor streptococcal activity and pediatric cartilage-toxicity concerns, making it the wrong class entirely
Question 2EENTEasy
A 12-year-old male has 2 days of sore throat, fever 39°C, tender anterior cervical lymph nodes, and tonsillar exudate. He has no cough or coryza. Which of the following is the most appropriate next step in management?
  • AAcetaminophen and reassurance
  • BRapid strep test or throat culture
  • CEmpiric oral amoxicillin
  • DThroat culture only, no testing
Reveal answer & full explanation
Correct answer: B — Rapid strep test or throat culture
  • AAcetaminophen and reassurance
  • BRapid strep test or throat culture✓
  • CEmpiric oral amoxicillin
  • DThroat culture only, no testing

Why Rapid strep test or throat culture is correct

  • This patient scores 4 on the Centor criteria: tonsillar exudate, tender anterior cervical lymph nodes, fever >38°C, and absence of cough
  • Modified Centor (McIsaac) criteria also incorporate age
  • With ≥3 Centor criteria, testing (rapid antigen detection test +/- culture) is indicated
  • Rapid strep is highly specific: a positive result warrants treatment
  • A negative rapid strep should be confirmed by throat culture in children (more sensitive) but not in adults

Why the others are wrong

  • Acetaminophen and reassurance — appropriate for 0-1 Centor criteria where no testing or treatment is needed; this patient has 4 criteria
  • Empiric oral amoxicillin — empiric amoxicillin without testing risks a rash if the cause is EBV mononucleosis rather than strep
  • Throat culture only, no testing — omitting the rapid strep test wastes time; rapid antigen testing is preferred upfront with culture as a backup in children if the rapid test is negative

Additional high-yield points

  • Score of 2: test if available
  • Treatment: penicillin V or amoxicillin for 10 days, or single-dose IM benzathine penicillin; cephalexin or clindamycin if penicillin-allergic
  • Goal of treatment: prevent rheumatic fever (not post-streptococcal glomerulonephritis), reduce symptom duration, prevent suppurative complications
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Risk factors

  • School-age children (5-15 years)
  • Close contact with infected individual
  • Late winter / early spring
  • Crowded living conditions (schools, military barracks)
  • Caregiver/parent of school-age child

Pathophysiology

S. pyogenes (Lancefield group A) adheres to pharyngeal epithelium via M protein, lipoteichoic acid, and fibronectin-binding proteins. Streptolysins and pyrogenic exotoxins cause local inflammation and systemic symptoms. Suppurative complications (peritonsillar abscess, otitis) arise from contiguous spread. Nonsuppurative sequelae (acute rheumatic fever, post-streptococcal glomerulonephritis) reflect immune-mediated cross-reactivity.

Clinical presentation

Symptoms

  • Sudden onset sore throat, painful swallowing
  • Fever ≥38°C (100.4°F)
  • Headache, malaise
  • Nausea, vomiting, abdominal pain (especially children)
  • ABSENCE of cough, rhinorrhea, conjunctivitis, hoarseness — strongly suggests GAS over viral

Signs / physical exam

  • Tonsillopharyngeal erythema with exudates
  • Tender anterior cervical lymphadenopathy
  • Palatal petechiae (uvular or soft palate)
  • Scarlatiniform rash (sandpaper-like), strawberry tongue, circumoral pallor → scarlet fever
  • Absence of viral features

Classic findings

Modified Centor (McIsaac) score components: fever >38, tonsillar exudate, tender anterior cervical adenopathy, absence of cough, age 3-14 (+1) or 15-44 (0) or ≥45 (-1).

Differential diagnosis

  • Viral pharyngitis (adenovirus, rhinovirus, coronavirus) — Cough, rhinorrhea, conjunctivitis, hoarseness, viral exanthem — argue AGAINST GAS; supportive care
  • Infectious mononucleosis (EBV) — Adolescent/young adult with fatigue, posterior cervical lymphadenopathy, palatal petechiae, splenomegaly, atypical lymphocytes; heterophile (Monospot) or EBV serology; rash develops in ~90% if amoxicillin given
  • Acute HIV (seroconversion) — Sore throat, fever, lymphadenopathy, mucocutaneous ulcers, rash; HIV RNA or 4th-gen antibody/antigen test
  • Gonococcal pharyngitis — Often asymptomatic; risk factors (oral sex, MSM); NAAT
  • Peritonsillar abscess — Trismus, deviated uvula, hot-potato voice; needs drainage
  • Retropharyngeal abscess — Neck stiffness, drooling, stridor; lateral neck XR or CT
  • Epiglottitis — Drooling, tripoding, muffled voice, severe sore throat with minimal pharyngeal findings; thumbprint sign on lateral neck XR
  • Diphtheria — Gray adherent pseudomembrane, unvaccinated; toxin neutralization required
  • Lemierre syndrome — Persistent fever after pharyngitis, unilateral neck pain/swelling, internal jugular vein thrombophlebitis with septic pulmonary emboli; usually Fusobacterium necrophorum
  • Kawasaki disease (children <5) — ≥5 days fever + 4 of 5 criteria (conjunctivitis, mucositis, rash, extremity changes, cervical lymphadenopathy); echo for coronary aneurysms

Diagnostic workup

Diagnostic criteria

IDSA 2012: confirm GAS pharyngitis with positive RADT or throat culture in symptomatic patients with clinical features suggestive of GAS (Centor ≥2-3); do not test those with overt viral features. Test of cure NOT routine.

Labs

  • Rapid antigen detection test (RADT) — sensitivity ~85%, specificity >95%
  • Throat culture (gold standard, ~90-95% sensitive) — required to confirm negative RADT in children/adolescents per IDSA; not necessary in adults given low GAS prevalence and minimal rheumatic fever risk
  • Do NOT test asymptomatic patients (high carriage rate, false positives)
  • Do NOT test patients with clear viral features (cough, coryza, conjunctivitis, hoarseness)
  • ASO and anti-DNase B titers — for documenting prior GAS infection in rheumatic fever evaluation, not acute diagnosis
  • Heterophile (Monospot) or EBV-specific serology if mononucleosis suspected

Imaging

  • Not required for uncomplicated GAS pharyngitis
  • Lateral neck XR or CT if epiglottitis, retropharyngeal abscess, or deep neck infection suspected

Diagnostic algorithm

Modified Centor CriterionPoints
Fever >38°C (100.4°F)+1
Absence of cough+1
Tender anterior cervical lymphadenopathy+1
Tonsillar exudate or swelling+1
Age 3-14 years+1
Age 15-44 years0
Age ≥45 years-1
Score 0-1: no testing, no antibiotic—
Score 2-3: RADT; treat if positive—
Score 4-5: RADT (some empiric treatment); culture if RADT negative in children—
Modified Centor (McIsaac) score for risk stratification of GAS pharyngitis.

Treatment

First-line

  • Penicillin V 500 mg PO BID-TID × 10 days (adults) OR amoxicillin 50 mg/kg/day (max 1000 mg) once daily × 10 days (children) — narrow-spectrum, low cost, no documented resistance
  • Penicillin G benzathine 1.2 million units IM × 1 (adults; 600,000 units if <27 kg) — single-dose option, ensures adherence
  • Supportive care: acetaminophen or NSAIDs, saltwater gargles, hydration
  • Treatment within 9 days of symptom onset prevents acute rheumatic fever; symptomatic improvement within 24-48 h
  • Return to school/work after 12-24 h of antibiotic therapy and afebrile

Second-line / adjunct

  • Penicillin allergy (non-anaphylactic): cephalexin 500 mg BID × 10 days, cefadroxil, or cefuroxime
  • Severe penicillin allergy: azithromycin × 5 days OR clindamycin × 10 days (check local macrolide resistance; rising in US ~5-15%)
  • Recurrent symptomatic GAS: confirm true infection (not carrier with intercurrent viral illness); consider clindamycin or amox-clav for re-treatment
  • Tonsillectomy considered for ≥7 episodes/year, ≥5/year × 2 years, or ≥3/year × 3 years (Paradise criteria) plus documentation in each

Complications

  • Suppurative: peritonsillar abscess, otitis media, sinusitis, retropharyngeal abscess, cervical lymphadenitis, Lemierre syndrome
  • Nonsuppurative — acute rheumatic fever (peaks 2-4 weeks after pharyngitis; PREVENTABLE by antibiotic treatment within 9 days)
  • Nonsuppurative — post-streptococcal glomerulonephritis (1-2 weeks after; NOT prevented by antibiotics; hematuria, edema, hypertension, low complement)
  • Scarlet fever (erythrogenic toxin)
  • Toxic shock syndrome and necrotizing fasciitis (rare, severe invasive disease)
  • PANDAS — pediatric autoimmune neuropsychiatric disorder (controversial)

PANCE pearls

  • Cough, coryza, conjunctivitis, hoarseness, oral ulcers → VIRAL. Do not test or treat for strep.
  • Centor/McIsaac score guides testing: ≥3 → RADT; <3 → no test, no antibiotic.
  • Amoxicillin given to mono produces a non-IgE-mediated maculopapular rash in 80-90% of patients — not a true penicillin allergy.
  • Antibiotics prevent acute rheumatic fever but NOT post-streptococcal glomerulonephritis.
  • No documented GAS resistance to penicillin — penicillin remains first-line; macrolide resistance rising.
  • Test-of-cure not recommended unless symptomatic recurrence or prior rheumatic fever.

References

  • IDSA 2012 — Shulman ST et al. Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis (Update). Clin Infect Dis 2012;55(10):e86-e102
  • AAP Red Book 2024 — American Academy of Pediatrics. Group A Streptococcal Infections. In: Red Book 2024
  • AHA — Gerber MA et al. Prevention of Rheumatic Fever and Diagnosis and Treatment of Acute Streptococcal Pharyngitis. Circulation 2009;119(11):1541-1551

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Commonly confused with

vs Peritonsillar Abscess

Related EENT diagnoses

Acute Otitis Media (AOM)Otitis Externa (Swimmer's Ear)Sensorineural and Conductive Hearing LossCerumen ImpactionAllergic RhinitisAcute Bacterial Rhinosinusitis (ABRS)Chronic Rhinosinusitis (CRS)EpistaxisPeritonsillar Abscess (Quinsy)Bacterial ConjunctivitisViral ConjunctivitisAllergic ConjunctivitisHordeolum (Stye) and ChalazionBlepharitis

Differentials & related conditions

Infectious Mononucleosis (EBV)EpiglottitisKawasaki Disease

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.