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 best explains why the respiratory tract is the most common portal of entry for pathogens?

Accepted Answer

It is constantly exposed to airborne particles and droplets.

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 and form dental plaque?

Accepted Answer

Glycocalyx made of dextran

Question 6

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 7

Which enzyme produced by bacteria digests fibrin clots, allowing the spread of infection?

Accepted Answer

Kinases

Question 8

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 9

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

Accepted Answer

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

Question 10

Which of the following statements about exotoxins is TRUE?

Accepted Answer

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

Question 11

A-B exotoxins act by:

Accepted Answer

Binding to host cells with the B component and disrupting cell function with the A component.

Question 12

Which of the following is a characteristic of endotoxins?

Accepted Answer

They are part of the lipopolysaccharide (LPS) layer of gram-negative bacteria.

Question 13

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

Accepted Answer

Lipid A of LPS (endotoxin)

Question 14

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

Accepted Answer

Limulus amebocyte lysate (LAL) assay

Question 15

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

Accepted Answer

Acquisition of diphtheria toxin gene by Corynebacterium diphtheriae

Question 16

Which cytopathic effect is commonly associated with rabies virus infection?

Accepted Answer

Formation of Negri bodies (inclusion bodies) in neurons

Question 17

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

Accepted Answer

Ergot alkaloids

Question 18

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 19

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

Accepted Answer

Respiratory tract (coughing and sneezing)

Question 20

Which of the following best explains why biofilms are difficult to eradicate in clinical settings?

Accepted Answer

Biofilm bacteria are shielded by extracellular polymeric substances, making them resistant to antibiotics and phagocytosis.

Ch .15 ppt Microbial Mechanisms of Pathogenicity: Study Notes

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