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 infected with a bacterium that produces a glycocalyx. What is the primary advantage this structure provides to the bacterium?

Accepted Answer

It impairs phagocytosis by host immune cells.

Question 3

Which of the following is the best definition of $$ID_{50}$$?

Accepted Answer

$$ID_{50} is $$the infectious dose required to infect 50\% of a sample population.

Question 4

Which of the following is NOT a portal of entry for pathogens?

Accepted Answer

Liver

Question 5

A bacterial pathogen produces coagulase. What is the function of this enzyme in pathogenesis?

Accepted Answer

It coagulates fibrinogen, forming a protective clot around the bacteria.

Question 6

Which of the following best explains why biofilms contribute to antimicrobial resistance?

Accepted Answer

Biofilms create a physical barrier that impedes the penetration of antibiotics and immune cells.

Question 7

A patient is infected with Streptococcus pyogenes. Which cell wall component helps this bacterium resist phagocytosis?

Accepted Answer

M protein

Question 8

Which of the following is a function of bacterial siderophores?

Accepted Answer

They bind iron more tightly than host iron-binding proteins, allowing bacteria to acquire iron.

Question 9

Which of the following statements about exotoxins is TRUE?

Accepted Answer

Exotoxins are proteins produced and secreted by both gram-positive and gram-negative bacteria.

Question 10

A patient develops fever and shock after a gram-negative bacterial infection. Which component is most likely responsible for these symptoms?

Accepted Answer

Lipid A portion of lipopolysaccharide (endotoxin)

Question 11

Which of the following best describes antigenic variation?

Accepted Answer

Pathogens alter their surface antigens, rendering host antibodies ineffective.

Question 12

Which of the following is a characteristic of A-B exotoxins?

Accepted Answer

They consist of an enzyme component (A part) and a binding component (B part).

Question 13

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

Accepted Answer

Respiratory tract via coughing and sneezing

Question 14

A patient is exposed to a toxin with an $$LD_{50} of$$ $$0.03\,ng/kg. $$What does this value indicate?

Accepted Answer

The toxin is extremely potent, requiring only a small amount to kill 50\% of the population.

Question 15

Which of the following is a cytopathic effect (CPE) caused by viral infection?

Accepted Answer

Formation of inclusion bodies in the host cell cytoplasm

Question 16

Which of the following toxins is produced by fungi and is known to be carcinogenic?

Accepted Answer

Aflatoxin

Question 17

A patient is infected with Neisseria gonorrhoeae. Which protein allows this bacterium to attach to host cells?

Accepted Answer

Opa protein

Question 18

Which of the following best describes the mechanism of action for invasins produced by Shigella and Listeria?

Accepted Answer

They rearrange actin filaments of the host cytoskeleton, causing membrane ruffling.

Question 19

Which of the following is a difference between exotoxins and endotoxins?

Accepted Answer

Exotoxins are proteins secreted by bacteria, while endotoxins are lipid components of the outer membrane of gram-negative bacteria.

Question 20

Which of the following is an example of a membrane-disrupting exotoxin?

Accepted Answer

Hemolysin

Microbial Mechanisms of Pathogenicity: Study Notes

Study Guide - Practice Questions