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 being bitten by an animal. Which portal of entry did the pathogen most likely use?

Accepted Answer

Parenteral route

Question 3

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

Accepted Answer

Mucous membranes of the respiratory tract

Question 4

The infectious dose for 50% of a sample population is known as:

Accepted Answer

$$ID_{50}$$

Question 5

Which structure allows Streptococcus mutans to adhere to teeth?

Accepted Answer

Glycocalyx made of dextran

Question 6

Which bacterial structure impairs phagocytosis and is associated with Streptococcus pneumoniae?

Accepted Answer

Capsule

Question 7

A patient is infected with Mycobacterium tuberculosis. Which cell wall component helps this bacterium resist digestion by phagocytes?

Accepted Answer

Waxy lipid (mycolic acid)

Question 8

Which enzyme produced by bacteria digests fibrin clots?

Accepted Answer

Kinases

Question 9

A patient is repeatedly infected with Neisseria gonorrhoeae despite previous infections. Which mechanism allows this pathogen to evade the immune system?

Accepted Answer

Antigenic variation

Question 10

Which of the following best describes the function of siderophores?

Accepted Answer

They bind iron more tightly than host iron-binding proteins.

Question 11

Which of the following statements about exotoxins is TRUE?

Accepted Answer

They are proteins produced and secreted by bacteria and are highly specific for their targets.

Question 12

Which type of exotoxin consists of an enzyme component and a binding component?

Accepted Answer

A-B toxin

Question 13

Which of the following is a characteristic of endotoxins?

Accepted Answer

They are composed of lipid A from the lipopolysaccharide layer of gram-negative bacteria.

Question 14

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

Accepted Answer

Release of endotoxin (lipid A) during bacterial lysis

Question 15

Which laboratory test is used to detect the presence of endotoxins in a sample?

Accepted Answer

Limulus amebocyte lysate (LAL) assay

Question 16

Which of the following is an example of lysogenic conversion increasing bacterial pathogenicity?

Accepted Answer

Acquisition of diphtheria toxin gene by Corynebacterium diphtheriae

Question 17

Which cytopathic effect is commonly used to diagnose rabies virus infection?

Accepted Answer

Presence of Negri bodies (inclusion bodies) in neurons

Question 18

Which fungal toxin is associated with hallucinations and is produced by Claviceps purpurea?

Accepted Answer

Ergot alkaloids

Question 19

A patient develops paralytic shellfish poisoning after eating contaminated mollusks. Which organism and toxin are most likely responsible?

Accepted Answer

Dinoflagellate Alexandrium producing saxitoxin

Question 20

Which portal of exit is most commonly used by pathogens that cause respiratory infections?

Accepted Answer

Respiratory tract (coughing and sneezing)

Microbial Mechanisms of Pathogenicity: Study Notes

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