Infectious Disease · Upper Respiratory Infections
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The primary pathogen in bacterial pharyngitis is Group A Streptococcus (GAS), also known as Streptococcus pyogenes.
The Centor Criteria is used to estimate the probability of GAS infection, consisting of tonsillar exudates, tender anterior cervical lymphadenopathy, fever, and absence of cough.
The gold standard for diagnosis is a throat culture, though rapid antigen detection testing (RADT) is frequently used due to high specificity, and molecular point-of-care testing (NAAT) is an increasingly used alternative with sensitivity approaching culture.
Penicillin V or Amoxicillin is the first-line treatment of choice to prevent acute rheumatic fever.
Patients with a non-anaphylactic penicillin allergy should receive a first-generation cephalosporin (e.g., cephalexin), while those with anaphylactic (IgE-mediated) allergy require a macrolide (e.g., azithromycin) or clindamycin.
Post-streptococcal glomerulonephritis is a potential complication that can occur regardless of whether the pharyngitis is treated with antibiotics.
Scarlet fever presents with a sandpaper-like rash, strawberry tongue, and circumoral pallor following a GAS infection.
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A 9-year-old boy is brought to the clinic by his mother due to a 3-day history of sore throat and fever. On physical examination, the patient has a temperature of 101.8°F (38.8°C), tonsillar exudates, and tender anterior cervical lymphadenopathy. He has no cough, rhinorrhea, or conjunctivitis. His lungs are clear to auscultation.
What is the most appropriate next step in management?
Rapid Antigen Detection Testing (RADT)
The patient meets the Centor criteria for high probability of GAS pharyngitis; therefore, diagnostic testing is required to confirm the infection before initiating antibiotic therapy.
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Etiology / Epidemiology
Caused by Group A Beta-Hemolytic Streptococcus (GABHS); peak incidence in ages 5-15.
Clinical Manifestations
Sudden onset fever, exudative pharyngitis, and tender anterior cervical lymphadenopathy.
Diagnosis
Throat culture is the gold standard; RADT allows rapid diagnosis; a negative RADT should be confirmed by throat culture in children and adolescents, but back-up culture is not routinely needed in adults.
Treatment
Penicillin V is the first-line treatment; anaphylaxis requires alternative therapy.
Prognosis
Self-limiting; rheumatic fever is the primary long-term complication to prevent.
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Epidemiology & Etiology
Primarily affects school-aged children via respiratory droplets. GABHS is the most common bacterial cause, though viral etiologies remain more frequent overall. Peak incidence occurs during winter and early spring.
Pertinent Anatomy
Infection involves the palatine tonsils and posterior pharyngeal wall. Inflammation leads to cervical lymphadenopathy due to lymphatic drainage from the oropharynx.
Pathophysiology
GABHS utilizes M-protein to evade phagocytosis and host immune responses. The inflammatory response triggers the classic exudative appearance. Untreated infection may lead to immune-mediated sequelae via molecular mimicry.
Clinical Manifestations
Classic presentation includes fever, tonsillar exudates, and tender anterior cervical lymphadenopathy. Absence of cough is a key clinical indicator. Red flags include trismus, uvular deviation, or drooling, suggesting a peritonsillar abscess.
Diagnosis
Use a clinical scoring system (Centor, McIsaac, or FeverPAIN) to estimate the probability of GABHS; IDSA (2025) suggests scoring chiefly to identify low-probability patients who do not need testing, and the recommendation does not apply to children under 3 years. The Rapid antigen detection test (RADT) is the preferred rapid test; throat culture remains the gold standard. Always perform a throat culture in children/adolescents if the rapid test is negative.
Treatment
Penicillin V is the first-line agent of choice. For non-anaphylactic penicillin allergy, use a first-generation cephalosporin (e.g., cephalexin); for anaphylactic allergy, use azithromycin or clindamycin. Anaphylaxis to penicillin necessitates avoiding all beta-lactams.
Prognosis
Symptoms typically resolve within 3-5 days with treatment. Prevention of acute rheumatic fever is the primary goal of antibiotic therapy. Post-streptococcal glomerulonephritis is not prevented by antibiotic treatment.
Differential Diagnosis
Viral Pharyngitis: presence of cough, rhinorrhea, and oral ulcers
Infectious Mononucleosis: posterior cervical lymphadenopathy and splenomegaly
Peritonsillar Abscess: trismus and uvular deviation
Epiglottitis: drooling, tripod position, and inspiratory stridor
Diphtheria: thick gray pseudomembrane