Question 1

Which of the following statements best distinguishes the three Domains of life: Bacteria, Archaea, and Eukarya?

Accepted Answer

Bacteria have peptidoglycan in their cell walls, Archaea have unique membrane lipids and lack peptidoglycan, and Eukarya possess membrane-bound organelles.

Question 2

A microbiologist is attempting to identify an unknown bacterial isolate. Which of the following methods would be most appropriate for distinguishing between two closely related bacterial species that are morphologically identical?

Accepted Answer

DNA fingerprinting

Question 3

Which of the following best describes the binomial naming system used in microbiology?

Accepted Answer

Each organism is assigned a two-part name: genus and species, both italicized.

Question 4

A patient is diagnosed with a disease caused by a prion. Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that lack nucleic acids.

Question 5

Which of the following is a key difference between the lytic and lysogenic cycles of bacteriophages?

Accepted Answer

The lytic cycle results in immediate destruction of the host cell, while the lysogenic cycle integrates the phage DNA into the host genome.

Question 6

A hospital is experiencing an increase in healthcare-associated infections (HAIs). Which of the following is the most effective step to reduce HAIs?

Accepted Answer

Implementing strict hand hygiene protocols among healthcare workers

Question 7

Which of the following best defines an opportunistic microbe?

Accepted Answer

A microbe that is part of the normal microbiota but can cause disease when the host's defenses are compromised

Question 8

Koch’s postulates are a set of criteria used to establish a causative relationship between a microbe and a disease. Which of the following is NOT one of Koch’s postulates?

Accepted Answer

The microorganism must be present in healthy individuals but absent in diseased individuals.

Question 9

Which of the following best explains the concept of herd immunity?

Accepted Answer

A population-level resistance to the spread of a contagious disease when a sufficient proportion of individuals are immune

Question 10

A patient develops a skin infection after a cut. The bacteria produce hyaluronidase. What is the role of hyaluronidase in pathogenesis?

Accepted Answer

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

Question 11

Which of the following is a defining characteristic of fungi?

Accepted Answer

They have cell walls made of chitin and obtain nutrients by absorption.

Question 12

A laboratory is using nucleic acid amplification tests (NAATs) to identify a pathogen. Which of the following best describes the principle behind NAATs?

Accepted Answer

They amplify specific DNA or RNA sequences of the pathogen using polymerase chain reaction (PCR).

Question 13

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

Accepted Answer

The B component binds to the host cell, allowing the A component to enter and disrupt cellular function.

Question 14

Which of the following is a key difference between exotoxins and endotoxins?

Accepted Answer

Exotoxins are secreted proteins, while endotoxins are lipopolysaccharides found in the outer membrane of Gram-negative bacteria.

Question 15

A patient is infected with a bacterium that produces siderophores. What is the function of siderophores in bacterial pathogenicity?

Accepted Answer

They bind and sequester iron from the host, making it available to the bacteria.

Question 16

Which of the following best describes the difference between direct damage and toxin production by pathogens?

Accepted Answer

Direct damage is caused by the physical presence and growth of the pathogen, while toxin production involves the release of harmful substances that affect host cells.

Question 17

A patient is diagnosed with a disease that is classified as 'endemic.' Which of the following best describes an endemic disease?

Accepted Answer

A disease that occurs at a constant, expected level in a specific geographic area.

Question 18

Which of the following is an example of a nonliving reservoir of infection?

Accepted Answer

A contaminated water supply

Question 19

A patient contracts a disease after eating undercooked meat containing parasitic cysts. Which portal of entry did the pathogen most likely use?

Accepted Answer

Gastrointestinal tract

Question 20

Which of the following best explains why re-emerging infectious diseases are becoming more common?

Accepted Answer

Antibiotic resistance, changes in human behavior, and global travel

Exam 3: Classification, Microbial Diversity, Viruses, and Pathogenesis

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