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 Bacillus anthracis via ingestion, inhalation, and skin contact. Based on the ID$$_{50}$$ values provided, which route is the most infectious?

Accepted Answer

Skin, because the ID$$_{50} is 10-50 $$endospores.

Question 3

Which toxin is the most potent based on the LD$$_{50}$$ values provided?

Accepted Answer

Botulinum toxin, because its LD$$_{50} is 0.03 ng/kg.$$

Question 4

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

Accepted Answer

Adherence of the pathogen to host cells.

Question 5

Which of the following is a function shared by capsules and M proteins in bacterial pathogenicity?

Accepted Answer

Both impair phagocytosis by host cells.

Question 6

Why does the influenza vaccine require annual updates, while many other vaccines provide years of protection?

Accepted Answer

Influenza virus undergoes frequent antigenic variation.

Question 7

Which enzyme allows bacteria to break down the polysaccharides that hold host cells together, facilitating tissue invasion?

Accepted Answer

Hyaluronidase

Question 8

How do siderophores contribute to bacterial pathogenicity?

Accepted Answer

They bind iron more tightly than host proteins, allowing bacteria to acquire essential nutrients.

Question 9

Which of the following best describes the mechanism of action of A-B exotoxins?

Accepted Answer

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

Question 10

A patient develops fever and shock after receiving a sterile cardiac catheter. The water used to wash the catheter was also sterile. What is the most likely explanation?

Accepted Answer

Endotoxins were present in the water, which are not destroyed by standard sterilization.

Question 11

Which of the following is NOT a cytopathic effect of viral infection?

Accepted Answer

Production of siderophores

Question 12

Which property distinguishes exotoxins from endotoxins?

Accepted Answer

Exotoxins are proteins, while endotoxins are lipopolysaccharides.

Question 13

Which of the following is a real-world example of antigenic variation?

Accepted Answer

The influenza virus changing its surface antigens each year.

Question 14

Which of the following is a portal of exit for pathogens?

Accepted Answer

All of the above (respiratory tract, gastrointestinal tract, blood)

Question 15

Which of the following mechanisms allows Mycobacterium tuberculosis to avoid destruction by phagocytes?

Accepted Answer

Resisting digestion due to a waxy lipid (mycolic acid) in its cell wall.

Question 16

Which of the following is a function of the Limulus amebocyte lysate (LAL) assay?

Accepted Answer

Detecting the presence of endotoxins in a sample.

Question 17

Which of the following is a virulence factor produced by fungi?

Accepted Answer

Trichothecene toxins that inhibit protein synthesis.

Question 18

Which of the following best explains why biofilms make bacteria more resistant to phagocytosis?

Accepted Answer

Biofilms shield bacteria with an extracellular polymeric substance (EPS).

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