Streptococcus pyogenes (Group A Streptococci)

Snapshot

A 6-year-old boy presents to his pediatrician for sore throat and a headache. His symptoms began approximately 2 days ago and have not improved. The mother reports that the patient appears uncomfortable and feels warm. She says that he was born at 39-weeks gestation via a normal spontaneous vaginal delivery with no complications. He has received all of his vaccinations appropriate for his age. He has no significant past medical history and only takes a daily multivitamin. He has no allergies to medications known to the mother. Physical examination is notable for perioral crusted lesions with tonsilar swelling with exudates. A rapid antigen detection test is positive for Streptococcal pyogenes infection. He is started on oral penicillin.

Introduction

Classification
- gram-positive cocci
Microbiology
- reservoir
- properties
  - Lacefield group A
  - β-hemolytic
  - bacitracin sensitive
  - pyrrolidonyl arylamidase (PYR) positive
  - hyaluronic acid capsule
    - inhibits phagocytosis
  - M protein
    - major virulence factor that inhibits complement activation and protects against phagocytosis
    - plasma cells create antibodies against this protein for opsonization
      - via molecular mimicry, this can lead to acute rheumatic fever
  - streptolysin O
    - an oxygen labile enzyme that destroys both red and white blood cells, giving this organism its β-hemolytic property
    - antibodies against streptolysin O (anti-ASO antibodies) allows checking ASO titers to determine if there was a recent Streptococcus pyogenes infection
  - DNase B
    - antibodies against DNase B (anti-DNase B) also indicate recent Streptococcus pyogenes infection
  - pyogenic exotoxin (erythrogenic toxin)
    - can result in scarlet fever
    - can superstimulate T-cells, resulting in streptococcal toxic shock syndrome
Associated conditions
- streptococcal pharyngitis
- streptococcal skin infections
- Scarlet fever
- delayed antibody-mediated reactions
  - rheumatic fever
  - poststreptococcal glomerulonephritis

Presentation

Diseases Associated with Streptococcal Pyogenes
Disease	Presentation	Diagnostic Studies	Treatment
Streptococcal pharyngitis	Symptomssore throatheadachePhysical examtonsillar enlargement without or with exudates feverlymphadenopathy	Rapid antigen detection test (RADT)high specificity (~95%)Throat culturehigh sensitivity (90-95%)	Penicillinprompt treatment prevents the development of rheumatic fever
Skin infections	Symptoms/physical examfolliculitisinfection of the hair folliclecellulitiserythematous, edematous, and warm skin impetigo vesicular and blistered skin lesions that flakes typically found by the mouth	Gram stain and culture	Dicloxacillincovers both Streptococcus pyogenes and Staphylococcus aureus
Scarlet fever	Symptoms/physical exam scarlet red rash begins on the trunk and neck and then spreads to the extremitiesa sand paper-like rashstrawberry tongue fever	Gram stain and culture	Penicillin
Rheumatic fever	Symptoms/physical examfeverchest pain (secondary to myocarditis)arthritis (acute migratory polyarthritis)choreadance-like movements of the extremities (2-3 weeks post pharyngitisNote that many years after the myocarditis, patients can develop rheumatic valvular diseasethe mitral valve is most commonly affected and the aortic valve is the second most common	Clinical diagnosistypically seen in untreated cases of streptococcal pharyngitis based on the Jones criteriahaving 2 major manifestations or 1 major manifestation plus 2 minor manifestations classifies the patient as having acute rheumatic feverMajor manifestationscarditis/valvulitisarthritisSydenham choreaMinor manifestationsarthralgiafever	Antibiotic prophylaxis with penicillinthe goal is to prevent recurrent streptococcal pharyngitis and acute rheumatic fever in order to decrease the risk of damaging the heart and its valves further
Poststreptococcal glomerulonephritis	Symptoms/physical examgeneralized edemahematuriahypertension	Based on both clinical and laboratory findingslaboratory findingspositive throat or skin culturepositive anti-ASO antibodies or streptozyme test	Penicillin if the streptococcal infection is still presentSupportive therapy

Streptococcus pyogenes (Group A Streptococci)

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