Question 1

Which of the following best defines virulence?

Accepted Answer

The degree of pathogenicity of a microorganism.

Question 2

A patient is exposed to Bacillus anthracis via inhalation, ingestion, and skin contact. Which portal of entry is considered parenteral?

Accepted Answer

Skin contact through a puncture wound

Question 3

If the ID$$_{50}$$ for Bacillus anthracis via skin is 10 spores, and via inhalation is 20,000 spores, what does this indicate about the relative effectiveness of these portals?

Accepted Answer

Skin is a more effective portal of entry than inhalation.

Question 4

Which of the following is a function of bacterial capsules in pathogenicity?

Accepted Answer

They make bacteria less susceptible to phagocytosis.

Question 5

Streptococcus pyogenes uses M protein as a virulence factor. What is the primary function of M protein?

Accepted Answer

It resists phagocytosis by host immune cells.

Question 6

Which exoenzyme allows Staphylococcus aureus to form clots and protect itself from host defenses?

Accepted Answer

Coagulase

Question 7

Trypanosoma brucei evades the host immune system by:

Accepted Answer

Undergoing antigenic variation.

Question 8

A-B toxins are a type of exotoxin. What is the role of the 'A' component in the A-B toxin mechanism?

Accepted Answer

It is responsible for the toxic enzymatic activity inside the cell.

Question 9

Which of the following statements about endotoxins is TRUE?

Accepted Answer

Endotoxins are released from the cell wall of gram-negative bacteria upon cell lysis.

Question 10

A patient develops fever after exposure to gram-negative bacteria. Which component is most likely responsible?

Accepted Answer

Lipid A portion of lipopolysaccharide

Question 11

Which of the following best describes the function of siderophores in bacterial pathogenicity?

Accepted Answer

They bind and transport iron from the host to the bacterium.

Question 12

Which of the following is a cytopathic effect commonly seen in viral infections?

Accepted Answer

Formation of inclusion bodies such as Negri bodies in rabies

Question 13

Amanita phalloides, the death cap mushroom, produces a mycotoxin called amanitin. What is the primary effect of this toxin?

Accepted Answer

It inhibits protein synthesis in host cells.

Question 14

Which of the following is a pathogenic effect of helminths?

Accepted Answer

Use of host tissue for growth and formation of masses such as elephantiasis

Question 15

Saxitoxin produced by certain algae is associated with which condition?

Accepted Answer

Paralytic shellfish poisoning

Question 16

Which of the following best describes antigenic variation?

Accepted Answer

The ability of a microbe to change its surface antigens to evade the host immune response.

Question 17

Which portal of exit is most commonly used by respiratory pathogens, and why?

Accepted Answer

Respiratory tract, because pathogens are expelled in droplets during coughing or sneezing.

Question 18

Which of the following is TRUE regarding the role of plasmids in microbial pathogenicity?

Accepted Answer

Plasmids can carry genes for toxin production and antibiotic resistance.

Question 19

A patient is infected with Streptococcus pyogenes, which produces streptolysins. What is the primary effect of these exotoxins?

Accepted Answer

They disrupt the host cell plasma membrane, causing lysis of red blood cells.

Question 20

Which of the following best describes the mechanism of action for superantigens?

Accepted Answer

They cause an excessive immune response by stimulating large numbers of T cells.

Mechanisms of Pathogenicity: Microbial Strategies and Host Interactions

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