$$NAD^+ + target\ protein \rightarrow ADP\text{-}ribosyl\text{-}target\ protein + nicotinamide$$

Question 1

Which of the following is NOT a step in bacterial pathogenesis?

Accepted Answer

Replication of host DNA

Question 2

Damage to the host during infection can occur by which of the following mechanisms?

Accepted Answer

All of the above

Question 3

Which statement best describes bacterial toxins?

Accepted Answer

They are proteins or cell wall components that, when purified, cause intoxication.

Question 4

Which of the following is a characteristic of endotoxins?

Accepted Answer

They are lipopolysaccharides found in Gram-negative bacteria.

Question 5

A-B toxins are classified based on the enzymatic function of the A subunit. Which of the following is NOT a function of the A subunit?

Accepted Answer

Phospholipase

Question 6

What is the role of the B subunit in A-B toxins?

Accepted Answer

Binds to the eukaryotic receptor and mediates uptake of the A subunit

Question 7

Which equation correctly represents the ADP-ribosylation reaction catalyzed by cholera toxin?

Accepted Answer

$$NAD^+ + target\ protein ightarrow ADP	ext{-}ribosyl	ext{-}target\ protein + nicotinamide$$

Question 8

Which of the following best describes the effect of cholera toxin on intestinal cells?

Accepted Answer

Permanently activates adenylate cyclase, increasing cAMP and chloride secretion

Question 9

The diphtheria toxin inhibits protein synthesis by modifying which cellular component?

Accepted Answer

Elongation factor 2 (EF-2)

Question 10

Which of the following toxins is classified as a metalloendoprotease and acts as a neurotoxin?

Accepted Answer

Botulinum toxin

Question 11

Which of the following is a consequence of N-glycosidase activity by Shiga toxin?

Accepted Answer

Inhibition of protein translation by hydrolysis of N-glycosidic bond in 28S rRNA

Question 12

Which of the following statements about superantigens is correct?

Accepted Answer

They cause excessive activation of T cells, leading to cytokine storm.

Question 13

Which of the following is a correct description of the mode of action of Clostridial toxins TcdA and TcdB?

Accepted Answer

They glycosylate small GTP-binding proteins, rendering them inactive.

Question 14

Which of the following is NOT a typical effect of bacterial toxins on host tissue?

Accepted Answer

Promotion of host cell DNA replication

Question 15

Which of the following is a distinguishing feature of exotoxins compared to endotoxins?

Accepted Answer

Exotoxins are proteins usually secreted by pathogens.

Question 16

Which of the following is a real-world consequence of the action of cholera toxin?

Accepted Answer

Severe diarrhea due to increased chloride and water secretion

Question 17

Which of the following toxins is most likely to cause death at the lowest dose, based on toxicity data?

Accepted Answer

Botulinum toxin

Question 18

Which of the following is a correct statement about the naming of bacterial toxins?

Accepted Answer

Toxins can be named according to species, affected organ, enzymatic activity, or symptoms.

Question 19

Which of the following is a target for vaccination to prevent toxin-mediated diseases?

Accepted Answer

AB toxins

Bacterial Pathogenesis and Toxins: Mechanisms and Effects

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