Question 1

Which of the following is the most common portal of entry for infectious microbes into the human body?

Accepted Answer

Respiratory tract

Question 2

A drug that binds mannose on human cells would most likely affect pathogenic bacteria by:

Accepted Answer

Preventing bacteria from binding to host cell receptors

Question 3

The virulence of a microbe is often measured by $$ID_{50}$$ and $$LD_{50}. If $$the $$LD_{50} of $$botulinum toxin is $$0.03\,	ext{ng/kg}$$ and the $$LD_{50} of $$Salmonella toxin is $$12\,	ext{mg/kg}$$, which toxin is more potent?

Accepted Answer

Botulinum toxin, because it requires less toxin to kill 50% of animals

Question 4

Which bacterial structure is primarily responsible for resisting phagocytosis by host immune cells?

Accepted Answer

Capsule

Question 5

A patient develops fever, chills, and hypotension after cardiac catheterization with sterile equipment washed in sterilized water containing Pseudomonas. What is the most likely cause of these symptoms?

Accepted Answer

Presence of endotoxins in the water

Question 6

Which enzyme produced by bacteria digests polysaccharides that hold cells together, resulting in tissue blackening and gangrene?

Accepted Answer

Hyaluronidase

Question 7

Antigenic variation allows pathogens to:

Accepted Answer

Evade the host immune response by altering surface antigens

Question 8

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

Accepted Answer

They bind to host cell receptors (B component) and deliver an enzymatic activity (A component) inside the cell

Question 9

Which property distinguishes exotoxins from endotoxins?

Accepted Answer

Exotoxins are proteins, while endotoxins are lipids

Question 10

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

Accepted Answer

Sequestering iron from host iron-transport proteins

Question 11

Which of the following is NOT a mechanism by which bacteria avoid destruction by phagocytes?

Accepted Answer

Producing siderophores to sequester iron

Question 12

Why does the influenza vaccine offer only a few months of protection, unlike many other vaccines?

Accepted Answer

Influenza virus undergoes antigenic variation, altering its surface antigens

Question 13

Which of the following is a cytopathic effect of viral infection?

Accepted Answer

Loss of contact inhibition leading to cancer

Question 14

Which virulence factor is shared by both fungi and bacteria to avoid phagocytosis?

Accepted Answer

Capsule

Question 15

Which portal of exit is most often used by pathogens to leave the host?

Accepted Answer

Respiratory tract

Question 16

A bacterium that produces both coagulase and kinase would:

Accepted Answer

Form and dissolve blood clots simultaneously, which is unlikely

Question 17

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

Accepted Answer

Gas gangrene

Question 18

How can lysogeny turn the normally harmless E. coli into a pathogen?

Accepted Answer

By incorporating a prophage that carries toxin genes

Question 19

Which of the following is a heat-stable toxin produced by algae that causes paralytic shellfish poisoning?

Accepted Answer

Saxitoxin

Question 20

Which of the following best describes the Limulus amebocyte lysate (LAL) assay?

Accepted Answer

It detects the presence of endotoxins by producing a gel-clot reaction

15 Microbial Mechanisms of Pathogenicity: Study Notes

Study Guide - Practice Questions

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