Question 1

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

Accepted Answer

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

Question 2

A patient develops a severe infection after a deep puncture wound. Which portal of entry did the pathogen most likely use?

Accepted Answer

Parenteral route

Question 3

The $$ID_{50}$$ for Bacillus anthracis via inhalation is 10,000–20,000 endospores, while via skin it is 10–50 endospores. What does this indicate about the preferred portal of entry?

Accepted Answer

Bacillus anthracis is more virulent when entering through the skin.

Question 4

Which of the following is the most potent toxin based on $$LD_{50}$$ values?

Accepted Answer

Botulinum toxin ($$LD_{50} = 0.03 ng/kg)$$

Question 5

A drug that binds mannose on human cells would most likely interfere with which step of microbial infection?

Accepted Answer

Adherence of pathogens to host cells

Question 6

Which bacterial structure is most directly involved in resisting phagocytosis?

Accepted Answer

Capsule

Question 7

Which enzyme allows bacteria to break down host connective tissue and spread through the body?

Accepted Answer

Collagenase

Question 8

Why does the influenza vaccine need to be updated frequently, unlike vaccines for diseases such as measles?

Accepted Answer

Influenza virus undergoes antigenic variation.

Question 9

How do siderophores contribute to bacterial pathogenicity?

Accepted Answer

They bind iron more tightly than host proteins, allowing bacteria to acquire essential nutrients.

Question 10

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, and the A component exerts the toxic effect inside the cell.

Question 11

Which of the following is a characteristic of endotoxins but not exotoxins?

Accepted Answer

They are part of the outer membrane of gram-negative bacteria and cause fever.

Question 12

A patient develops fever and shock after receiving a sterile cardiac catheter. The water used to wash the catheter was also sterile. What is the most likely explanation?

Accepted Answer

Endotoxins were present in the water and should have been tested using the LAL assay.

Question 13

Which cytopathic effect is commonly associated with rabies virus infection?

Accepted Answer

Formation of Negri bodies (inclusion bodies) in the cytoplasm

Question 14

Which of the following is a virulence factor for fungi that contributes to their pathogenicity?

Accepted Answer

Production of proteases that modify host cell membranes

Question 15

A patient develops paralytic shellfish poisoning after eating contaminated mollusks. Which organism and toxin are most likely responsible?

Accepted Answer

Dinoflagellate Alexandrium producing saxitoxin

Question 16

Which portal of exit is most commonly used by pathogens responsible for respiratory infections?

Accepted Answer

Respiratory tract (coughing and sneezing)

Question 17

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

Accepted Answer

Biofilms resist antibiotics and disinfectants and shield bacteria from phagocytosis.

Question 18

Which of the following is an example of lysogenic conversion increasing bacterial pathogenicity?

Accepted Answer

Acquisition of diphtheria toxin gene by Corynebacterium diphtheriae

Question 19

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

Accepted Answer

Secretion of siderophores to acquire iron

Microbial Mechanisms of Pathogenicity: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards