[LBBBI20] [LE1] STREPTOCOCCUS PYOGENES (GROUP A)

Fimbriae: Protein F

Attachment and adherence

M protein

Resistance to phagocytosis

Hyaluronic acid capsule

Prevents phagocytosis

Lipoteichoic acid

Adheres to molecules on host epithelial cells

Hemolysin

Streptolysin O (O2 labile)

Streptolysin S (O2 stable)

Where is Streptolysin O2 labile (promotes breakdown of oxygen)?

detected in ASO titers

Where is Streptolysin S O2 stable?

causes hemolysis on plates

What does erythrogenic toxin/streptococcal pyogenic exotoxin?

scarlet fever

What are enzymes?

Streptokinase

DNAses

Hyaluronidase - "spreading factor"

Clinical Conditions: Streptococcus pyogenes

Pyodermal infections

Impetigo: weeping lesion

Erysipelas

Cellulitis

Wound infections

Scarlet fever

Starts with pharyngitis and causes rash on trunk and extremities

Due to untreated Group A infections

What is Invasive Group A Streptococcal Infections?

Streptococcal toxic shock syndrome, Cellulitis, Rheumatic Fever, Acute glomerulonephritis (AGN)

Streptococcal toxic shock syndrome

Multiorgan system failure similar to staphylococcal toxic shock

Initial infection may have been pharyngitis, cellulitis, peritonitis, or other wound infections

Cellulitis

Severe form of infection that is life-threatening

Bacteremia and sepsis may occur

In patients necrotizing fasciitis, edema, erythema, and pain in the affected area may develop

Streptococcal myositis resembles clostridial gangrene

Rheumatic fever

Fever

Inflammation of the heart, joints, blood vessels, and subcutaneous tissues

Chronic, progressive damage to the heart valves (most evidence favors cross-reactivity between Streptococcal antigens and heart tissue)

ASO titer will be elevated

Acute glomerulonephritis (AGN)

Follows either cutaneous or pharyngeal infections

More common in children than adults

Antigen-antibody complexes deposit in the glomerulus

Inflammatory responses causes damage to the glomerulus and impairs the kidneys

Streptococcus pyogenes

Catalase-negative

Bacitracin-susceptible

PYR-positive

Hippurate hydrolysis-negative

Slide agglutination