Bacterial Toxins Overview

Study Notes

Toxins are classified as exotoxins (proteins) and endotoxins (lipid molecules from the cell membrane).
Exotoxins can be excreted or released through cell lysis, while endotoxins are integral to the bacterial structure.

Clostridium perfringens Alpha Toxin:
- A lecithinase that damages cell membranes by splitting lecithin into phosphorylcholine and diglyceride.
Staphylococcus aureus TSST-1:
- Causes Toxic Shock Syndrome; characterized by shock, high fever, diffuse red rash that desquamates.
- Induces large interleukin-2 (IL-2) and tumor necrosis factor (TNF) production through T-cell stimulation.
- Systemic effects resemble those caused by lipopolysaccharides.
Streptococci Pyrogenic Exotoxin A:
- Similar to TSST-1; associated with scarlet fever and rapid soft tissue infections.
- Acts as a super antigen affecting T-cell activation.

Vibrio cholerae Enterotoxin:
- Enters via contaminated food/drink, attaches to intestinal microvilli.
- Produces a large enterotoxin (MW of 84,000) causing massive secretory diarrhea and electrolyte loss.
Staphylococcus aureus Enterotoxin:
- Produced in improperly refrigerated food (meat/dairy).
- Symptoms occur rapidly after ingestion, primarily causing vomiting and sometimes diarrhea.
- Recognized as the most common form of food poisoning.

Comprised of two subunits, A (toxic effect) and B (aids adherence).
- Subunit A increases adenylate cyclase activity leading to raised cAMP levels.
- Results in massive electrolyte secretion into the gut, causing severe diarrhea and potential acidosis.

Lipopolysaccharides (LPS):
- Found in gram-negative bacterial cell walls, released upon bacterial lysis.
- Heat-stable with molecular weights ranging from 3000 to several million.
- Trigger inflammatory responses and septic shock when released in large quantities.