Question 1

Which of the following best describes the difference between pathogenicity and virulence?

Accepted Answer

Pathogenicity refers to the ability to cause disease, while virulence refers to the degree of pathogenicity.

Question 2

A patient develops pneumonia after inhaling a pathogen. Which portal of entry did the pathogen most likely use?

Accepted Answer

Mucous membranes of the respiratory tract

Question 3

Which of the following is the best definition of $$ID_{50}$$?

Accepted Answer

$$ID_{50} is $$the infectious dose required to cause disease in 50% of a sample population.

Question 4

Bacillus anthracis has different $$ID_{50}$$ values depending on the portal of entry. Which portal requires the highest number of endospores to cause infection?

Accepted Answer

Ingestion

Question 5

A bacterial pathogen produces a glycocalyx that enables it to adhere to teeth and resist phagocytosis. Which two virulence factors are being described?

Accepted Answer

Capsules and adhesins

Question 6

Which enzyme allows bacteria to break down host connective tissue by digesting collagen?

Accepted Answer

Collagenase

Question 7

A patient is infected with Neisseria gonorrhoeae, which uses Opa protein to attach to host cells. Which cell wall component is responsible for this attachment?

Accepted Answer

Opa protein

Question 8

Which of the following best explains why biofilms are difficult to eradicate in clinical settings?

Accepted Answer

Biofilm bacteria are shielded by extracellular polymeric substances (EPS), making them more resistant to antibiotics and phagocytosis.

Question 9

A bacterial pathogen secretes siderophores. What is the primary function of these molecules?

Accepted Answer

To bind iron more tightly than host iron-binding proteins

Question 10

Which of the following statements about exotoxins is TRUE?

Accepted Answer

Exotoxins are proteins secreted by bacteria that are highly specific for their targets.

Question 11

A patient develops symptoms of fever, nausea, vomiting, diarrhea, shock, and death after exposure to a bacterial toxin that triggers massive cytokine release from T cells. Which type of exotoxin is most likely responsible?

Accepted Answer

Superantigen

Question 12

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

Accepted Answer

The B component binds to the host cell, allowing the A component to enter and exert its enzymatic effect.

Question 13

Which of the following is a characteristic effect of endotoxins (Lipid A of LPS) on the human body?

Accepted Answer

They stimulate macrophages to release large quantities of cytokines, leading to fever and shock.

Question 14

A pharmaceutical company wants to test a new batch of intravenous drugs for endotoxin contamination. Which assay should they use?

Accepted Answer

Limulus amebocyte lysate (LAL) assay

Question 15

Which of the following is an example of antigenic variation as a virulence factor?

Accepted Answer

A virus changes its surface antigens so that host antibodies are no longer effective.

Question 16

Which of the following best explains why Mycobacterium tuberculosis is resistant to digestion by phagocytes?

Accepted Answer

It has a waxy lipid (mycolic acid) in its cell wall.

Question 17

A patient is diagnosed with paralytic shellfish poisoning after eating contaminated mollusks. Which microbial group is responsible for producing the neurotoxin involved?

Accepted Answer

Algae (dinoflagellates)

Question 18

Which of the following is a multi-step process that allows Salmonella to invade intestinal epithelial cells?

Accepted Answer

Rearrangement of host actin filaments by invasins, causing membrane ruffling and engulfment of the bacteria

Question 19

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

Accepted Answer

Plasmids may carry genes for toxins, antibiotic resistance, and virulence factors.

Question 20

A patient is infected with a virus that causes host cells to fuse into a multinucleated giant cell (syncytium). This is an example of which type of viral effect?

Accepted Answer

Cytopathic effect (CPE)

Microbial Mechanisms of Pathogenicity: Chapter 15 Study Notes

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