Question 1

Which of the following best describes the role of virulence factors in the outcome of infectious disease?

Accepted Answer

Virulence factors determine the severity and progression of disease by enabling pathogens to evade host defenses and cause damage.

Question 2

A patient presents with symptoms of pneumonia. According to Koch’s Postulates, which step is necessary to confirm that a specific bacterium is the causative agent?

Accepted Answer

The bacterium must be isolated from the diseased individual and grown in pure culture.

Question 3

Which of the following routes of transmission is most likely responsible for the spread of cholera in a population?

Accepted Answer

Oral-fecal route via contaminated water

Question 4

A histogram shows a sharp increase in cases of influenza over a short period in a city. Which epidemiological term best describes this event?

Accepted Answer

Epidemic

Question 5

Which of the following is a property of innate immunity that distinguishes it from adaptive immunity?

Accepted Answer

Innate immunity is always present and acts rapidly against most microbes.

Question 6

Which of the following is NOT a first line of innate defense against pathogens?

Accepted Answer

Antibody production by plasma cells

Question 7

During phagocytosis, which step involves the fusion of the phagosome with a lysosome to form a phagolysosome?

Accepted Answer

Maturation

Question 8

Which complement pathway is initiated by antibodies binding to antigens?

Accepted Answer

Classical pathway

Question 9

The Membrane Attack Complex (MAC) formed by complement proteins is most effective against which type of bacteria?

Accepted Answer

Gram-negative bacteria

Question 10

Which class of antibody is primarily responsible for mucosal immunity and is found in secretions such as saliva and tears?

Accepted Answer

IgA

Question 11

A graph shows a rapid increase in IgM followed by a slower, sustained increase in IgG after exposure to a pathogen. What does this pattern indicate?

Accepted Answer

Acute primary infection

Question 12

Which T-cell subset is responsible for killing infected cells through the perforin-granzyme pathway?

Accepted Answer

Cytotoxic T-cells (Tc)

Question 13

Which MHC molecule presents antigens from intracellular pathogens to cytotoxic T-cells?

Accepted Answer

MHCI

Question 14

A patient develops an allergic reaction to pollen. Which type of hypersensitivity is most likely involved?

Accepted Answer

Type I (Immediate hypersensitivity)

Question 15

Which mechanism allows Listeria monocytogenes to evade the immune system and spread within the host?

Accepted Answer

Moving from cell-to-cell using actin-based motility without exiting the cells

Question 16

Why are vaccines against Neisseria gonorrhoeae generally ineffective?

Accepted Answer

The bacterium rapidly mutates its surface antigens, preventing effective immune recognition.

Question 17

Which viral mechanism is used by HIV to evade the host immune response?

Accepted Answer

Rapid mutation of surface antigens and entering latency

Question 18

Antigenic drift and antigenic shift are important concepts in viral evolution. Which equation best represents the probability $$P of a $$new viral strain emerging due to antigenic shift, given mutation rate $$\mu$$ and recombination rate $$r$$?

Accepted Answer

$$P = 1 - e$$^{- (\mu + r) t}$$

Question 19

VDJ recombination in immune cells allows for which of the following?

Accepted Answer

Generation of diverse antigen receptors to recognize a wide range of pathogens

Question 20

A patient with sepsis is experiencing a cytokine storm. Which of the following best describes the impact of this event?

Accepted Answer

Overwhelming inflammation leading to tissue damage and potential organ failure

MCB 100 Exam 3 Study Guide: Infection, Immunity, and Pathogen Evasion

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