17.E: Pathogenicity and Virulence Factors (Exercises)
- Page ID
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Virulence factors contribute to a pathogen’s ability to cause disease. Exoenzymes and toxins allow pathogens to invade host tissue and cause tissue damage. Exoenzymes are classified according to the macromolecule they target and exotoxins are classified based on their mechanism of action. Bacterial toxins include endotoxin and exotoxins. Endotoxin is the lipid A component of the LPS of the gram-negative cell envelope. Exotoxins are proteins secreted mainly by gram-positive bacteria.
Multiple Choice
Which of the following would be a virulence factor of a pathogen?
- a surface protein allowing the pathogen to bind to host cells
- a secondary host the pathogen can infect
- a surface protein the host immune system recognizes
- the ability to form a provirus
- Answer
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A
You have recently identified a new toxin. It is produced by a gram-negative bacterium. It is composed mostly of protein, has high toxicity, and is not heat stable. You also discover that it targets liver cells. Based on these characteristics, how would you classify this toxin?
- superantigen
- endotoxin
- exotoxin
- leukocidin
- Answer
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C
Which of the following applies to hyaluronidase?
- It acts as a spreading factor.
- It promotes blood clotting.
- It is an example of an adhesin.
- It is produced by immune cells to target pathogens.
- Answer
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A
Phospholipases are enzymes that do which of the following?
- degrade antibodies
- promote pathogen spread through connective tissue.
- degrade nucleic acid to promote spread of pathogen
- degrade cell membranes to allow pathogens to escape phagosomes
- Answer
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D
Fill in the Blank
The glycoprotein adhesion gp120 on HIV must interact with __________ on some immune cells as the first step in the process of infecting the cell.
- Answer
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CD4
Adhesins are usually located on __________ of the pathogen and are composed mainly of __________ and __________.
- Answer
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surface; proteins; sugars
The Shiga and diphtheria toxins target __________ in host cells.
- Answer
-
protein synthesis
Antigenic __________ is the result of reassortment of genes responsible for the production of influenza virus spike proteins between different virus particles while in the same host, whereas antigenic __________ is the result of point mutations in the spike proteins.
- Answer
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shift; drift
Critical Thinking
Two types of toxins are hemolysins and leukocidins. (a) How are these toxins similar? (b) How do they differ?
Imagine that a mutation in the gene encoding the cholera toxin was made. This mutation affects the A-subunit, preventing it from interacting with any host protein. (a) Would the toxin be able to enter into the intestinal epithelial cell? (b) Would the toxin be able to cause diarrhea?