S. pyogenes

STREPTOCOCCUS PYOGENES

Structure

Is a gram + bacteria, capsulated, no spore former, usually as strains, facultative anaerobic, hemolytic. Perform β- hemolysis, and can be classified by his wall carbohydrate (Lancefield) or by his M protein.

Pathogenesis and virulence factors

Adhesion: Requires M protein, F protein, Capsule, Lipoteicoic Acid – Links Epithelium fibrinogen.

Internalization: Use M protein and F protein.

Anti-phagocyte Characteristics: M protein can bind to H factor that inactivate C3b, and bind fibrinogen that blocks C3b membrane union. MRP (M related proteins) binds to albumin, fibrinogen, IgA and IgG, plasminogen that inhibits phagocyte function. Otherwise, Capsule has intrinsic anti-phagocyte function. C5a peptidase can cut this chemocine.

Invasion: It’s up to M protein and Capsule.

Tissue Spread: DNA nuclease can eliminate DNA residues, hialuronidase allow tissue transition, streptoquinase allow the bacteria cut a clot and spread to all tissues, Cystein protease can eliminate cell residue.

Periphery Toxicity: Encompasses O streptolisine, S streptolisine and Sp-exotoxines.
SpeA:STSS

Epidemiology

There are some nasal carriers, and transmission is: oral and nasal secretions, rheumatic fever occurs after pharingytis, acute glomerulonephritis occurs after skin or respiratory infection.

Pathology Spectrum

Pharingoamigdalitis, erisipel, impetigo, scarlatin fever, necrotizing fasciitis.

Auto-immune: Rheumatic fever, glomerulonephritis.

Exotoxine Disease: Scarlet fever and STSS.

Rheumatic Fever: Has a latency period od 20 days, is recurrent and long time effects. Disease occurs when M protein mimics tropomyosin and myosin. Also, Group A carbohydrate mimics a valvular glycoprotein, Is not related with genus or race but economic status.

Jones’s Diagnostic Criteria: with 2 mayors or 1 mayor with 2 minor’s factors.
Mayor’s: Migratory poliarthritis, carditis, marginal erythema, subcutaneous nodes and chorea.
Minor’s: Fever, arthralgia, elevated PCR or GSS, and PR increase on EKG.
Chorea: Molecular mimicry for losoganlioside and N-acetyl glucosamine.

Panda’s: Same last mechanism but different expression: obsessive compulsive disease, TIC’s and tourette syndrome.

Glomerulonephritis: Express like a nephritic syndrome because a molecular mimicry of M protein with kidney’s basement membrane and complex deposit. A latency period of 1 month.