Question 1

Which of the following best describes the function of the capsule as a pathogenic factor?

Accepted Answer

It helps bacteria evade phagocytosis by host immune cells.

Question 2

A patient develops flaccid paralysis after consuming improperly canned food. Which toxin is most likely responsible, and what is its mechanism of action?

Accepted Answer

Botulinum toxin; inhibits acetylcholine release at neuromuscular junctions, causing paralysis.

Question 3

Which of the following statements about endotoxins is CORRECT?

Accepted Answer

Endotoxins are lipid A components of LPS in Gram-negative bacteria and can cause septic shock.

Question 4

A laboratory test reveals a bacterial protein that non-specifically stimulates T cell proliferation and massive cytokine release, including TNF. Which term best describes this protein?

Accepted Answer

Superantigen

Question 5

Which of the following is a function of the M protein in Streptococcus pyogenes?

Accepted Answer

It facilitates attachment to host cells and resists phagocytosis.

Question 6

Which of the following best explains why exotoxins are generally more toxic than endotoxins?

Accepted Answer

Exotoxins are proteins with specific targets and high potency, while endotoxins are less specific and less potent.

Question 7

A patient with a Gram-negative bacterial infection develops a sudden drop in blood pressure and multi-organ failure. Which component of the bacteria is most likely responsible for this clinical presentation?

Accepted Answer

Lipid A of lipopolysaccharide (LPS)

Question 8

Which of the following is a characteristic of A-B exotoxins?

Accepted Answer

The A component is the active (toxic) part, and the B component is for binding.

Question 9

Which of the following best describes the action of cholera toxin?

Accepted Answer

It binds intestinal epithelial cells, disrupts membrane function, and causes loss of electrolytes and water.

Question 10

Which of the following is a common feature of superantigens?

Accepted Answer

They cause non-specific activation of T cells and massive cytokine release.

Question 11

A patient is diagnosed with diphtheria. Which mechanism best explains the cytotoxic effect of the diphtheria toxin?

Accepted Answer

It inhibits protein synthesis in host cells by inactivating elongation factor 2.

Question 12

Which of the following is NOT a typical portal of entry for pathogenic microorganisms?

Accepted Answer

Mitochondria

Question 13

Which of the following best describes the role of fimbriae in bacterial pathogenicity?

Accepted Answer

They facilitate attachment of bacteria to host tissues.

Question 14

Which of the following equations best represents the relationship between the dose of a toxin and its effect, where $$E is $$the effect, $$D is $$the dose, and $$K is a $$constant?

Accepted Answer

$$E = \frac{D}{K + D}$$

Question 15

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

Accepted Answer

Endotoxins are heat-stable and part of the outer membrane of Gram-negative bacteria.

Question 16

A patient is exposed to a bacterial toxin that causes spastic paralysis by blocking inhibitory neurotransmitter release. Which toxin is responsible?

Accepted Answer

Tetanus toxin

Question 17

Which of the following best explains why superantigens can be life-threatening?

Accepted Answer

They induce massive, non-specific activation of T cells, leading to a cytokine storm.

Question 18

Which of the following is a real-world example of a disease caused by an enterotoxin?

Accepted Answer

Cholera

Question 19

Which of the following best describes the difference between the portals of entry and portals of exit for pathogens?

Accepted Answer

Portals of entry are the sites where pathogens enter the host, while portals of exit are the sites where pathogens leave the host.

Mechanisms of Pathogenicity: Key Concepts and Factors ~ Chp 15

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