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Updated: Feb 28 2019

Streptococcus pyogenes (Group A Streptococci)

Images a strep classification - moises.jpg
  • 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
      • Symptoms
        • sore throat
        • headache
      • Physical exam
        • tonsillar enlargement without or with exudates 
        • fever
        • lymphadenopathy
      • Rapid antigen detection test (RADT)
        • high specificity (~95%)
      • Throat culture
        • high sensitivity (90-95%)
      • Penicillin
        • prompt treatment prevents the development of rheumatic fever 
      • Skin infections
      • Symptoms/physical exam
        • folliculitis
          • infection of the hair follicle
        • cellulitis
          • erythematous, edematous, and warm skin 
        • impetigo 
          • vesicular and blistered skin lesions that flakes
            • typically found by the mouth
      • Gram stain and culture
      • Dicloxacillin
        • covers 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 extremities
          • a sand paper-like rash
        • strawberry tongue 
        • fever
      • Gram stain and culture
      • Penicillin
      • Rheumatic fever
      • Symptoms/physical exam
        • fever
        • chest pain (secondary to myocarditis)
        • arthritis (acute migratory polyarthritis)
        • chorea
          • dance-like movements of the extremities (2-3 weeks post pharyngitis
      • Note that many years after the myocarditis, patients can develop rheumatic valvular disease
        • the mitral valve is most commonly affected and the aortic valve is the second most common
      • Clinical diagnosis
        • typically seen in untreated cases of streptococcal pharyngitis 
        • based on the Jones criteria
          • having 2 major manifestations or 1 major manifestation plus 2 minor manifestations classifies the patient as having acute rheumatic fever
      • Major manifestations
        • carditis/valvulitis
        • arthritis
        • Sydenham chorea
      • Minor manifestations
        • arthralgia
        • fever
      • Antibiotic prophylaxis with penicillin
        • the 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 exam
        • generalized edema
        • hematuria
        • hypertension
      • Based on both clinical and laboratory findings
        • laboratory findings
          • positive throat or skin culture
          • positive anti-ASO antibodies or streptozyme test
      • Penicillin if the streptococcal infection is still present
      • Supportive therapy
    • Rapid antigen detection test (RADT)
      • high specificity (~95%)
    • Throat culture
      • high sensitivity (90-95%)
    • Penicillin
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