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 attaching to host cells

Question 3

The virulence of a microbe is often measured by $$ID_{50}$$ and $$LD_{50}. $$What does $$ID_{50}$$ represent?

Accepted Answer

The number of pathogen cells or virions required to cause infection in 50% of inoculated animals

Question 4

If the $$LD_{50}$$ for botulinum toxin is $$0.03\,	ext{ng/kg}$$ and for Salmonella toxin is $$12\,	ext{mg/kg}$$, which toxin is more potent?

Accepted Answer

Botulinum toxin

Question 5

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

Accepted Answer

Capsule

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

Alter their surface antigens to evade the host immune response

Question 8

How do bacteria such as Salmonella use the host cell’s cytoskeleton to enter the cell?

Accepted Answer

By rearranging actin filaments, causing membrane ruffling

Question 9

Which mechanism is NOT used by bacteria to avoid destruction by phagocytes?

Accepted Answer

Requirement for high pH in phagolysosome

Question 10

Biofilms contribute to pathogenicity by:

Accepted Answer

Shielding bacteria from phagocytosis and immune recognition

Question 11

Siderophores are important for bacterial pathogens because they:

Accepted Answer

Sequester iron from host iron-transport proteins

Question 12

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

Accepted Answer

Exotoxins are secreted proteins, endotoxins are lipid components of Gram-negative bacteria

Question 13

Which type of exotoxin causes an intense immune response by stimulating the release of cytokines from T cells?

Accepted Answer

Superantigen

Question 14

The Limulus amebocyte lysate (LAL) assay is used to detect:

Accepted Answer

Endotoxins

Question 15

Plasmids can contribute to bacterial pathogenicity by:

Accepted Answer

Carrying genes for toxins and antibiotic resistance

Question 16

Which cytopathic effect is NOT typically caused by viral infection?

Accepted Answer

Increasing host cell contact inhibition

Question 17

Which fungal toxin is carcinogenic and produced by Aspergillus species?

Accepted Answer

Aflatoxin

Question 18

Protozoa can evade host defenses by:

Accepted Answer

Digesting host cells and tissue fluids, growing in phagocytes, and antigenic variation

Question 19

Which portal of exit is most commonly used by pathogens?

Accepted Answer

Respiratory tract

Question 20

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?

Accepted Answer

Presence of endotoxins in the water

Microbial Mechanisms of Pathogenicity: How Microorganisms Cause Disease

Study Guide - Practice Questions

Study Guide - Flashcards