Streptococcus pyrogenes Flashcards
What is the Gram morphology of S. pyrogenes?
Gram-positive (cocci in chains) and also beta-hemolytic
What is streptococcal typing based on?
Based on cell wall carbohydrates
What types of infections can S. pyrogenes cause?
Pharyngitis, tonsillitis
Impetigo
Cellulitis, erysipelas
Childbed fever = sepsis
Necrotizing fascitis
What is a post-infectious disease caused by S. pyrogenes?
Acute glomerulonephritis rheumatic fever
What are some of the virulence factors of S. pyrogenes?
M protein
Hyaluronic acid capsule
Streptococcal toxins and enzymes
What does M protein do?
Binds extracellular matrixes
Antiphagocytic
Binds fibrinogen
Binds the Fc portion of IgG
binds complement factor H
REQUIRED TO CAUSE DISEASE - strains that lack M protein are not virulent
What is M protein encoded by?
emm gene
What about M protein makes it invasive?
Can bind to extracellular structures such as collagen and fibronectin
What is the purpose of the hyaluronic acid capsule in S. pyrogenes?
Anti-phagocytic
Some strains are very mucoid
Can be associated with rheumatic fever
What is streptokinase?
Dissolves blood clots - fibrin
What is hyaluronidase?
Breaks down connective tissue
What are deoxyribonucleases?
Degrades DNA
What is erythrogenic toxin?
Causes the rash of Scarlet fever - superantigen
What are Spe toxins?
Superantigens sometimes present in NF strains, are exotoxins that cause massive tissue damage and inflammation like flesh-eating disease
How is S. pyrogenes transmitted?
Initially colonizes the skin and pharynx
Person-to-person spread (skin contact or respiratory droplets)
Less common is food or waterborne
