Pathogenesis (Dr. A)

Exotoxin Characteristics

- A-B toxins (intracellular acting) - membrane disrupting (surface damaging) - superantigens - extracellular enzymes

Endotoxin Characteristics

- cell wall associated toxins - elicit a strong immune response

3 types of membrane-disrupting toxins (exotoxin)

1. enzymes that hydrolyze phospholipids (phospholipase, sphingomyelinase) 2. toxins with detergent-like surfactant activity 3. pore-forming toxins

3 roles of exotoxins in disease

1. ingestion of preformed toxin (botulism) 2. colonization of wound or surface 3. aid growth and spread in tissues

A-B toxins (exotoxin)

Intracellular acting B portion binds to specific host cell receptor

How does endotoxin activate the complement and coagulation cascades?

LPS binds proteins in plasma LPS binds CD14 CD14-LPS binds TLR4 on macrophages and monocytes Macrophages and monocytes release cytokines which trigger PGE and leukotriene release

Toxic portion of LPS (endotoxin)

Lipid A

How is a septic shock response triggered in gram-positive bacteria since they lack LPS?

TLR2 binds lipoproteins/teichoic acids

Pathogenicity

capacity of an organism to cause disease

Virulence Factor

characteristic or structure that contributes to the ability of a microbe to cause disease

Extracellular Enzymes: Coagulase

clots fibrin to protect bacteria (exotoxin)

Superantigens (exotoxin)

crosslinking causes stimulation of up to 1 in 5 T cells

Virulence

degree of pathogenicity

What does the Limulus amebocyte lysate (LAL) assay measure?

the amount of endotoxin