Question 1

Which of the following best describes the function of adhesins (ligands) in microbial pathogenicity, as illustrated in the first image?

Accepted Answer

They bind specifically to complementary receptors on host cell surfaces, facilitating adherence.

Question 2

A patient develops necrotizing fasciitis, as shown in one of the images. Which bacterial enzyme is most likely responsible for the rapid tissue destruction observed in this condition?

Accepted Answer

Collagenase

Question 3

Which of the following best explains why Bacillus anthracis is more infectious via the skin than by ingestion, based on the ID50 values provided?

Accepted Answer

A lower ID50 for skin means fewer endospores are needed to cause infection compared to ingestion.

Question 4

Which of the following statements about exotoxins is correct?

Accepted Answer

Exotoxins are proteins, usually produced by gram-positive bacteria, and can be neutralized by antitoxins.

Question 5

A patient is infected with Neisseria gonorrhoeae. Which cell wall component helps this bacterium evade the immune system?

Accepted Answer

Opa protein

Question 6

Which of the following best describes the mechanism of action for A-B exotoxins?

Accepted Answer

The B component binds to the host cell receptor, allowing the A component to enter and alter cell function.

Question 7

Which of the following is a characteristic of endotoxins?

Accepted Answer

They are lipid A components of lipopolysaccharides in gram-negative bacteria.

Question 8

A patient develops a fever after a gram-negative bacterial infection. Which sequence best describes the mechanism leading to fever?

Accepted Answer

Endotoxin stimulates macrophages to release cytokines, which travel to the hypothalamus and induce prostaglandin production, raising body temperature.

Question 9

Which of the following best explains antigenic variation as a mechanism for immune evasion, as seen in trypanosomes?

Accepted Answer

The pathogen alters its surface antigens, allowing it to evade the host immune response over time.

Question 10

Which of the following enzymes allows Streptococcus pyogenes to break down blood clots and spread through tissues?

Accepted Answer

Streptokinase

Question 11

A bacterial pathogen is able to survive inside macrophages by resisting digestion. Which cell wall component is responsible for this property in Mycobacterium tuberculosis?

Accepted Answer

Mycolic acid

Question 12

Which of the following is a real-life example of a biofilm, as discussed in the study materials?

Accepted Answer

Dental plaque on teeth

Question 13

Which portal of exit is most likely for a pathogen that causes respiratory symptoms?

Accepted Answer

Respiratory tract

Question 14

Which of the following best describes the effect of superantigens on the host immune system?

Accepted Answer

They cause an intense immune response by stimulating massive cytokine release, which can result in shock and death.

Question 15

Which of the following is the best definition of LD50?

Accepted Answer

The dose of a toxin or pathogen that is lethal to 50% of the affected subjects.

Question 16

Which of the following is NOT a portal of entry for pathogens?

Accepted Answer

Lymphatic vessels

Question 17

Which of the following statements about the relationship between exotoxins and lysogenic conversion is correct?

Accepted Answer

Lysogenic conversion can result in bacteria acquiring the ability to produce exotoxins.

Question 18

Which of the following best describes the action of membrane-disrupting toxins?

Accepted Answer

They form protein channels or disrupt the phospholipid bilayer, causing cell lysis.

Question 19

Which of the following is a correct statement about the neutralization of toxins?

Accepted Answer

Exotoxins can be neutralized by specific antibodies called antitoxins.

Microbial Mechanisms of Pathogenicity

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