Question 1

Which of the following best describes an opportunistic pathogen?

Accepted Answer

A pathogen that causes disease only in immunocompromised individuals.

Question 2

Which of the following is the correct sequence of events in bacterial pathogenesis?

Accepted Answer

Portal of entry → Adherence → Colonization and invasion → Damage to host → Exit from host

Question 3

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

Accepted Answer

$$ID_{50}$$

Question 4

Which of the following virulence factors allows Streptococcus pneumoniae to evade phagocytosis?

Accepted Answer

Capsule

Question 5

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

Accepted Answer

Lipid A of lipopolysaccharide (LPS)

Question 6

Which of the following statements about exotoxins is TRUE?

Accepted Answer

They are proteins, often with A-B subunit structure, and can be inactivated by heat.

Question 7

Which enzyme produced by bacteria helps them spread by breaking down connective tissue?

Accepted Answer

Collagenase

Question 8

A strain of E. coli acquires a plasmid that codes for toxin production. This is an example of:

Accepted Answer

Horizontal gene transfer increasing virulence

Question 9

Which of the following best explains why some bacteria can evade the immune system by changing their surface antigens?

Accepted Answer

Antigenic variation

Question 10

Which of the following is a characteristic of endotoxins but NOT exotoxins?

Accepted Answer

Heat stability and inability to be converted to toxoids

Question 11

A patient with a wound infection caused by Staphylococcus aureus develops toxic shock syndrome. Which type of toxin is most likely involved?

Accepted Answer

Superantigen

Question 12

Which of the following best describes the mechanism of an A-B exotoxin?

Accepted Answer

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

Question 13

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

Accepted Answer

Liver

Question 14

Which of the following is a real-life example of a disease caused by a membrane-disrupting exotoxin?

Accepted Answer

Gas gangrene caused by Clostridium perfringens

Question 15

Which of the following best explains why infants and elderly are more susceptible to infections?

Accepted Answer

They have impaired or less robust immune defenses.

Question 16

A patient with HIV develops pneumonia caused by Pneumocystis jirovecii. This is an example of:

Accepted Answer

An opportunistic infection

Question 17

Which of the following is a function of bacterial pili in pathogenesis?

Accepted Answer

Attachment to host cell surfaces

Question 18

Which of the following is a possible portal of exit for pathogens?

Accepted Answer

All of the above (Respiratory tract, Gastrointestinal tract, Blood)

Question 19

Which of the following best describes the effect of superantigens?

Accepted Answer

They cause an intense immune response by stimulating massive cytokine release.

Question 20

Which of the following is a mechanism by which protozoa evade host defenses?

Accepted Answer

Antigenic variation

Microbial Mechanisms of Pathogenicity: Study Notes

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