Q4 Urgent Caring- 20 Questions (and Answers) About Strep Pharyngitis

Michael Weinstock, MD & Gita Pensa, MD


What infectious organisms can cause pharyngitis?

  • Viruses
  • Bacteria
  • Fungi

What are non-strep causes of throat pain?

  • Peritonsillar abscess
  • Gonorrhea
  • Retropharyngeal abscess
  • Diphtheria (more common in Russia)
    • Epiglottitis – Now a disease of adults that presents more gradually
  • Herpes simplex virus
  • Mononucleosis
  • Post-cervical lymphadenopathy (LAN)
  • Fatigue
  • Splenomegaly
  • Mechanical
    • Foreign body
    • Mass
  • Allergic rhinitis
  • Cancer of the head and neck
  • Gastroesophageal reflux disease

What is the specific name for the bacteria that causes strep?

  • Group A strep pharyngitis (caused by Streptococcus pyogenes)
  • Exhibits complete hemolysis (beta hemolysis) when grown on agar 
  • Part of the group A Lancefield classification system
  • Name: Group A beta hemolytic strep (GABHS)

What are historical features of GABHS pharyngitis? 

  • Sore throat
  • Pain with swallowing
  • Fever
  • Other: Headache, abdominal pain, nausea/vomiting (in children)
  • Note: Do not have cough, rhinorrhea, oral ulcers, conjunctivitis

What are the exam findings of GABHS?

  • Erythema pharynx and tonsils
  • Tonsillar hypertrophy
  • Exudates (not always present)
  • Palatal petechiae (up to 95% specific for GABHS)
  • Anterior cervical lymphadenopathy

What are the Centor criteria?

  • Fever
  • Anterior cervical LAN
  • Tonsillar exudate
  • No cough

What is the risk of strep throat based on the Centor criteria?

  • If all 4 are present (score = 4), risk of GABHS is 51%-53%
  • If none are present (score = 0), risk of GABHS is 1%-2.5%

How is strep transmitted?

  • Spread directly from person to person from respiratory droplets, saliva, nasal secretions
  • More likely to spread from symptomatic compared to asymptomatic carriers 
  • Increased in schools, daycare centers, military training facilities
  • Pets CANNOT transmit
  • Decreased ability to transmit after 12 hours of antibiotics
  • Centers for Disease Control and Prevention (CDC) recommends staying home until (1) afebrile, AND (2) 12-24 hours after starting antibiotics

What is the incubation period?

  • 2-5 days

In what groups is testing not routinely indicated? 

  • Children younger than 3 years
  • Adults
  • Note: Acute rheumatic fever (ARF) is very rare in the above age groups
  • Note: GABHS is most common in patients 5-15 years old

When should a culture be done?

  • In children, a culture is recommended if the rapid antigen detection test (RADT) is negative
  • In adults, a culture is not recommended
  • (Culture may not be necessary with rapid PCR – more sensitive than antigen testing)

What are the suppurative complications of GABHS?

  • Acute rheumatic fever 
  • Peritonsillar abscess
  • Mastoiditis
  • Cervical lymphadenitis

Why do we treat GABHS?

  • Shortens duration of symptoms (per CDC). Note: CDC confirms that symptoms are usually self-limited
  • Reduces transmission 
  • Prevents complications (suppurative complications) 

Who should not be treated?

  • Patients with viral or noninfectious pharyngitis

Which antibiotics should be used?

  • There has never been a report of a clinical isolate of group A strep that is resistant to penicillin (PCN); cephalosporins are reasonable in PCN-allergic patients
  • Resistance to azithromycin (rising resistance levels) and clarithromycin common in some communities

What dose of PCN should be used?

  • PCN: Children 250 mg twice a day (BID) or 3 times a day (TID), adults 250 mg 4 times a day (QID)
  • Amoxicillin: 50 mg mg/kg once a day (QD) or 25 mg mg/kg BID

What is the duration of therapy?

  • 10 days (recent studies suggest that 5 days may be nearly as good)

Which antibiotic should be used in patients with a PCN allergy?

  • Narrow-spectrum cephalosporins, clindamycin, azithromycin

Should those with asymptomatic group A strep (carriers) be treated?

  • Asymptomatic group A strep carriers usually do not require treatment. Carriers will likely have a positive throat culture or be RADT positive, but do not have clinical symptoms or an immunologic response. Carriers are much less likely to transmit and are also very unlikely to develop suppurative or nonsuppurative complications.
  • A patient with viral pharyngitis may test positive for strep but be a carrier. Repeated use of antibiotics in the group is unnecessary. The Infectious Diseases Society of America (IDSA) has more information on identifying carriers.

Is the risk of post-strep glomerulonephritis decreased with antibiotics?

  • This is a nonsuppurative sequela that occurs after the original infection and is thought to be from an immune response, not from the direct group A strep infection.


Pharyngitis (Strep Throat). Centers for Disease Control and Prevention.
https://www.cdc.gov/groupastrep/diseases-hcp/strep-throat.html#:~:text=Clinical%20features,-Group%20A%20strep&text=Other%20symptoms%20may%20include%20headache,strongly%20suggest%20a%20viral%20etiology (Last Reviewed: June 27, 2022)

Diagnosis and treatment of streptococcal pharyngitis
Choby BA. Am Fam Physician. 2009;79(5):383-390. [published correction appears in Am Fam Physician. 201;88(4):222. Dosage error in article text].