Question 1

Which of the following best describes the difference between infection and intoxication in microbial disease processes?

Accepted Answer

Infection involves the multiplication of microorganisms in the host, while intoxication is caused by ingestion of pre-formed toxins without microbial multiplication.

Question 2

A patient develops muscle rigidity and spasms after a puncture wound. Which neurotoxin is most likely responsible, and what is its mechanism of action?

Accepted Answer

Tetanospasmin; it blocks the release of inhibitory neurotransmitters, causing spastic paralysis.

Question 3

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 are released upon cell lysis.

Question 4

A foodborne illness occurs after eating improperly stored potato salad. The patient experiences vomiting within 4 hours. Which of the following best explains the pathogenesis?

Accepted Answer

Intoxication by ingestion of pre-formed S. aureus enterotoxin.

Question 5

Which of the following best describes the action of cholera toxin in the intestinal epithelium?

Accepted Answer

It activates adenylate cyclase, increasing cAMP and causing secretion of electrolytes and water into the lumen.

Question 6

Which of the following is a portal of entry for pathogens, as described in the study materials?

Accepted Answer

Gastrointestinal tract

Question 7

A patient with Gram-negative sepsis develops a high fever. Which of the following best explains the mechanism by which endotoxin causes fever?

Accepted Answer

Endotoxin stimulates macrophages to release interleukin-1, which acts on the hypothalamus to raise body temperature.

Question 8

Which of the following is NOT a typical effect of viral cytopathic effect (CPE) observable under a light microscope?

Accepted Answer

Production of interferon by infected cells

Question 9

Which of the following best describes the role of adhesion factors in microbial pathogenicity?

Accepted Answer

They allow microbes to attach to host cell receptors, facilitating colonization.

Question 10

A patient is diagnosed with diphtheria. The gene for the diphtheria toxin is located on which of the following genetic elements?

Accepted Answer

Lysogenic bacteriophage

Question 11

Which of the following equations best represents the relationship between the number of invading microbes ($$N$$), the probability of infection ($$P$$), and the infectious dose 50 ($$ID_{50}$$)?

Accepted Answer

$$P = 1 - e$$^{-N/ID_{50}$$}$$

Question 12

Which of the following is a function of hyaluronidase produced by certain bacteria?

Accepted Answer

It degrades hyaluronic acid in connective tissue, facilitating the spread of bacteria.

Question 13

Which of the following statements about exotoxins is TRUE?

Accepted Answer

They are proteins that can be inactivated by heat and converted to toxoids for vaccines.

Question 14

A patient presents with flaccid paralysis after eating home-canned food. Which of the following best explains the pathogenesis?

Accepted Answer

Ingestion of pre-formed botulinum toxin blocks acetylcholine release at neuromuscular junctions.

Question 15

Which of the following is a common portal of exit for respiratory pathogens?

Accepted Answer

Coughing and sneezing through the respiratory tract

Question 16

Which of the following best explains why the myxoma virus did not eradicate the rabbit population in Australia?

Accepted Answer

Co-evolution led to increased resistance in rabbits and decreased virulence in the virus.

Question 17

Which of the following is a cytopathic effect (CPE) that can be used to diagnose rabies infection?

Accepted Answer

Presence of Negri bodies in neurons

Question 18

Which of the following is a real-life example of a disease caused by an enterotoxin?

Accepted Answer

Cholera

Question 19

Which of the following best describes the function of interferon produced by virus-infected cells?

Accepted Answer

It signals neighboring cells to produce antiviral proteins that block viral replication.

Microbial Mechanisms of Pathogenicity and Disease Processes

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