Question 1

Which of the following best describes 'normal biota' and its role in human health?

Accepted Answer

A collection of microbes that colonize the body and can manufacture vitamins, compete with pathogens, and promote immune maturation.

Question 2

A patient develops a Clostridioides difficile infection after a course of antibiotics. This is an example of:

Accepted Answer

Dysbiosis

Question 3

Which of the following is a characteristic of an opportunistic pathogen?

Accepted Answer

It causes disease only when the host's defenses are compromised or when it enters an unusual site.

Question 4

The infectious dose (ID-50) is defined as:

Accepted Answer

The number of cells or virions needed to establish an infection in 50% of exposed hosts.

Question 5

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

Accepted Answer

Bone marrow

Question 6

Fimbriae, capsules, and spikes are all examples of:

Accepted Answer

Adhesion factors that help microbes attach to host cells

Question 7

Biofilms are clinically significant because:

Accepted Answer

They make microbes up to 1,000 times more resistant to antibiotics.

Question 8

Which enzyme allows bacteria to break down connective tissue and invade deeper tissues?

Accepted Answer

Hyaluronidase

Question 9

A pathogen that periodically alters its surface molecules to evade the immune system is using which strategy?

Accepted Answer

Antigenic variation

Question 10

Which of the following best describes the difference between endotoxins and exotoxins?

Accepted Answer

Endotoxins are lipid A components of Gram-negative bacteria released upon cell death, while exotoxins are proteins secreted by both Gram-positive and Gram-negative bacteria.

Question 11

A patient develops septic shock after being treated with antibiotics for a Gram-negative bacterial infection. This is most likely due to:

Accepted Answer

Release of endotoxins (lipid A) from dying bacteria

Question 12

Which of the following is a Type III exotoxin?

Accepted Answer

Botulinum toxin

Question 13

A microbe that can exist inside macrophages to evade the immune system is using which strategy?

Accepted Answer

Intracellular survival

Question 14

Which of the following is a function of siderophores produced by bacteria?

Accepted Answer

Snatching iron from host proteins like transferrin

Question 15

Which of the following is NOT a way that pathogens can undermine the immune system?

Accepted Answer

Stimulating the production of more phagocytes

Question 16

A microbe that is still infectious but weakened and does not cause disease in an immunocompetent host is described as:

Accepted Answer

Attenuated

Question 17

Which of the following is a real-life example of microbial antagonism?

Accepted Answer

Normal gut microbiota preventing the overgrowth of pathogenic bacteria

Question 18

Which of the following statements about the portals of exit for pathogens is TRUE?

Accepted Answer

They are often similar to the portals of entry.

Question 19

Which of the following is a plausible outcome if a pathogen cannot adhere to host tissues?

Accepted Answer

It will be unable to establish infection.

Question 20

Which of the following best explains why ID-50 and LD-50 values can vary between hosts?

Accepted Answer

Differences in host genetics and immune fitness

Host–Microbe Interactions and Virulence Factors: Structured Study Notes

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