Bacterial Toxins Overview

Questions and Answers

What mechanism do N. gonorrhoeae employ to enhance their invasion of host cells?

Releasing exotoxins to induce cell lysis

Forming biofilms to obstruct immune response

Using pili and Opacity Associated Proteins (Opa) as adhesins (correct)

Utilizing endotoxins to destroy host cells

How does the intracellular survival of gonococci occur after phagocytosis by polymorphonuclear cells?

By inducing apoptosis in host immune cells

By multiplying within the vesicle formed during engulfment (correct)

Through the production of exotoxins that kill the host cells

By escaping into the cytoplasm undetected

What are the components of the exotoxin produced by C. diphtheriae?

Peptidoglycan and teichoic acids

Single polypeptide chains that function independently

Two subunits, A and B, each with distinct functions (correct)

Lipopolysaccharides and glycoproteins

Which characteristic is correct about endotoxins in bacteria?

They are lipid molecules found in bacterial cell membranes Signup and view all the answers

Which process characterizes coiling phagocytosis as observed with legionellae?

Development of a vesicle that remains intact during bacterial replication Signup and view all the answers

What is the primary mechanism by which the alpha toxin of C perfringens causes cell damage?

Splitting lecithin to phosphorylcholine and diglyceride Signup and view all the answers

How does toxic shock syndrome toxin-1 (TSST-1) primarily affect the immune response?

By stimulating T-cells to produce large amounts of IL-2 and TNF Signup and view all the answers

What characterizes the systemic effects of TSST-1 in toxic shock syndrome?

Similar effects to those caused by lipopolysaccharides Signup and view all the answers

What type of toxin is produced by some strains of group A β-hemolytic streptococci and resembles TSST-1?

Pyrogenic exotoxin A Signup and view all the answers

What is the primary action of V. cholerae enterotoxin once it enters the host?

It penetrates the intestinal mucosa and attaches to microvilli Signup and view all the answers

Study Notes

Bacterial Toxins Overview

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.

Key Exotoxins

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.

Enterotoxins

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.

C.diphtheriae Exotoxin

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.

Endotoxin Characteristics

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.

Description

Explore the fascinating world of bacterial toxins, including the differences between exotoxins and endotoxins. Learn about key exotoxins such as Clostridium perfringens Alpha Toxin, Staphylococcus aureus TSST-1, and the role of enterotoxins like Vibrio cholerae Enterotoxin. This quiz will enhance your understanding of their mechanisms and effects.