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 develops pneumonia after inhaling droplets containing a pathogenic bacterium. Which portal of entry did the pathogen most likely use?

Accepted Answer

Respiratory tract

Question 3

Which of the following best defines $$ID_{50}$$?

Accepted Answer

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

Question 4

Which of the following is the most common portal of entry for pathogens?

Accepted Answer

Respiratory tract

Question 5

A patient receives a deep puncture wound and develops tetanus. Which portal of entry did the pathogen most likely use?

Accepted Answer

Parenteral route

Question 6

Which of the following is a function of bacterial adhesins?

Accepted Answer

They bind to specific receptors on host cells, facilitating adherence.

Question 7

Which enzyme allows bacteria to break down host connective tissue by digesting collagen?

Accepted Answer

Collagenase

Question 8

A bacterial pathogen is able to avoid destruction by phagocytes by producing a glycocalyx capsule. Which disease is most associated with this mechanism?

Accepted Answer

Pneumonia caused by Streptococcus pneumoniae

Question 9

Which of the following best describes antigenic variation?

Accepted Answer

Pathogens alter their surface antigens to evade the host immune response.

Question 10

Which of the following is a characteristic of exotoxins?

Accepted Answer

They are proteins produced and secreted by bacteria, often highly specific and potent.

Question 11

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

Accepted Answer

Lipid A of lipopolysaccharide (endotoxin)

Question 12

Which of the following best explains the mechanism of action of an A-B exotoxin?

Accepted Answer

The B component binds to the host cell, allowing the A component to enter and disrupt cellular function.

Question 13

Which laboratory test is used to detect the presence of endotoxins in pharmaceutical products?

Accepted Answer

Limulus amebocyte lysate (LAL) assay

Question 14

Which of the following is a cytopathic effect of viral infection?

Accepted Answer

Formation of syncytia (multinucleated giant cells)

Question 15

A patient develops paralytic shellfish poisoning after eating contaminated mollusks. Which type of microorganism is responsible?

Accepted Answer

Algae producing saxitoxin

Question 16

Which of the following is a property of endotoxins but NOT exotoxins?

Accepted Answer

They are heat-stable and can withstand autoclaving at $$121^\circC $$for 1 hour.

Question 17

Which of the following mechanisms allows Shigella and Listeria to move from one host cell to another?

Accepted Answer

They use actin polymerization to propel themselves through the cytoplasm.

Question 18

Which of the following is a function of siderophores produced by bacteria?

Accepted Answer

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

Question 19

Which of the following is a mechanism by which biofilms contribute to pathogenicity?

Accepted Answer

Biofilms shield bacteria from phagocytosis and increase resistance to antibiotics.

Question 20

Which of the following is a portal of exit for pathogens that is also a portal of entry?

Accepted Answer

Respiratory tract

Microbial Mechanisms of Pathogenicity: Study Notes

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