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Questions and Answers
What mechanism do N. gonorrhoeae employ to enhance their invasion of host cells?
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?
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?
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?
Which characteristic is correct about endotoxins in bacteria?
Which process characterizes coiling phagocytosis as observed with legionellae?
Which process characterizes coiling phagocytosis as observed with legionellae?
What is the primary mechanism by which the alpha toxin of C perfringens causes cell damage?
What is the primary mechanism by which the alpha toxin of C perfringens causes cell damage?
How does toxic shock syndrome toxin-1 (TSST-1) primarily affect the immune response?
How does toxic shock syndrome toxin-1 (TSST-1) primarily affect the immune response?
What characterizes the systemic effects of TSST-1 in toxic shock syndrome?
What characterizes the systemic effects of TSST-1 in toxic shock syndrome?
What type of toxin is produced by some strains of group A β-hemolytic streptococci and resembles TSST-1?
What type of toxin is produced by some strains of group A β-hemolytic streptococci and resembles TSST-1?
What is the primary action of V. cholerae enterotoxin once it enters the host?
What is the primary action of V. cholerae enterotoxin once it enters the host?
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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.
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