Question 1

Which of the following best describes the difference between pathogenicity and virulence?

Accepted Answer

Pathogenicity is the ability to cause disease, while virulence is the degree of pathogenicity.

Question 2

A patient is exposed to two bacterial toxins: Toxin A has an $$LD_{50} of$$ $$0.03$$ nanograms/kg, and Toxin B has an $$LD_{50} of$$ $$12$$ milligrams/kg. Which toxin is more potent and why?

Accepted Answer

Toxin A is more potent because a lower $$LD_{50}$$ means less toxin is needed to be lethal.

Question 3

Which of the following is NOT a principal portal of entry for microorganisms?

Accepted Answer

Lymphatic vessels

Question 4

A drug that binds to mannose on human cells would most likely interfere with which step of microbial infection?

Accepted Answer

Adherence of pathogens to host cells

Question 5

Which of the following best explains why Streptococcus pneumoniae with a capsule is more virulent than without?

Accepted Answer

The capsule impairs phagocytosis by host immune cells.

Question 6

Which enzyme produced by bacteria digests the polysaccharides that hold host cells together, facilitating tissue invasion?

Accepted Answer

Hyaluronidase

Question 7

Antigenic variation allows pathogens to:

Accepted Answer

Alter their surface antigens to evade the host immune response.

Question 8

Which of the following is a mechanism by which bacteria can survive inside phagocytes?

Accepted Answer

Preventing fusion of the lysosome with the phagosome

Question 9

Siderophores contribute to bacterial pathogenicity by:

Accepted Answer

Binding iron more tightly than host cells, allowing bacteria to acquire essential nutrients.

Question 10

Which of the following statements about exotoxins is TRUE?

Accepted Answer

Exotoxins are proteins produced and secreted by bacteria, often with specific targets in the host.

Question 11

A-B toxins, a type of exotoxin, function by:

Accepted Answer

The B component binds to the host cell, and the A component exerts the toxic effect.

Question 12

Which of the following is a characteristic effect of endotoxins?

Accepted Answer

They cause fever by inducing the release of cytokines and prostaglandins.

Question 13

The Limulus amebocyte lysate (LAL) assay is used to detect:

Accepted Answer

Endotoxins

Question 14

Which of the following is an example of a cytopathic effect caused by viral infection?

Accepted Answer

Formation of a syncytium (fusion of cells)

Question 15

Which virulence factor is associated with the ability of fungi to evade phagocytosis?

Accepted Answer

Capsule formation

Question 16

A patient develops fever, chills, and hypotension after cardiac catheterization with sterile equipment washed in sterilized water. The most likely cause is:

Accepted Answer

Endotoxins present in the water, which should have been tested with the LAL assay.

Question 17

Which of the following is a portal of exit commonly used by pathogens?

Accepted Answer

Respiratory tract via coughing and sneezing

Question 18

Which of the following best explains why the influenza vaccine does not provide long-term protection?

Accepted Answer

The influenza virus undergoes antigenic variation, changing its surface antigens.

Question 19

Which of the following is a mechanism by which protozoa avoid host defenses?

Accepted Answer

Antigenic variation

Question 20

Which of the following statements about plasmids and lysogeny is correct?

Accepted Answer

Plasmids may carry genes for toxins, and lysogeny can convert harmless bacteria into pathogens.

Microbial Mechanisms of Pathogenicity: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards