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 trying to identify an unknown bacterial species. Which of the following methods would be most useful for distinguishing between two closely related bacterial strains that are morphologically identical?

Accepted Answer

DNA fingerprinting

Question 3

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

Accepted Answer

It assigns a unique two-part name consisting of genus and species, such as $$	extit{Escherichia coli}.$$

Question 4

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

Accepted Answer

The lysogenic cycle allows the viral genome to persist in the host cell without causing immediate destruction, while the lytic cycle leads to rapid host cell lysis.

Question 5

A hospital patient develops a urinary tract infection after catheterization. This infection is best classified as:

Accepted Answer

A hospital-acquired infection (HAI)

Question 6

Which of the following best explains why Koch’s postulates cannot always be applied to identify the cause of a disease?

Accepted Answer

Some pathogens cannot be cultured in artificial media.

Question 7

Which of the following is a defining characteristic of fungi?

Accepted Answer

They are eukaryotic, have chitin in their cell walls, and obtain nutrients by absorption.

Question 8

A patient is diagnosed with a disease that is constantly present at a low level in a population. This disease is best described as:

Accepted Answer

Endemic

Question 9

Which of the following best describes the function of siderophores in bacterial pathogenicity?

Accepted Answer

They bind iron from the host environment, making it available for bacterial growth.

Question 10

A patient is infected with a bacterium that produces an A-B toxin. Which of the following best describes the mechanism of action of this toxin?

Accepted Answer

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

Question 11

Which of the following is a major reason for the re-emergence of infectious diseases in the modern world?

Accepted Answer

Increased use of antibiotics leading to resistant strains

Question 12

Which of the following best distinguishes between exotoxins and endotoxins?

Accepted Answer

Exotoxins are secreted proteins that can be produced by both Gram-positive and Gram-negative bacteria, while endotoxins are lipopolysaccharides found in the outer membrane of Gram-negative bacteria.

Question 13

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

Accepted Answer

A contaminated water supply

Question 14

A patient is exposed to a pathogen through a cut in the skin. Which portal of entry is involved?

Accepted Answer

Parenteral route

Question 15

Which of the following best describes the role of capsules in bacterial pathogenicity?

Accepted Answer

Capsules help bacteria resist phagocytosis by host immune cells.

Question 16

A patient is infected with a microbe that produces hyaluronidase. What is the likely effect of this enzyme?

Accepted Answer

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

Question 17

Which of the following best describes herd immunity?

Accepted Answer

It is the resistance of a population to infection due to a high proportion of individuals being immune.

Question 18

Which of the following is a characteristic of prions that distinguishes them from viruses?

Accepted Answer

Prions are infectious proteins that lack nucleic acids.

Question 19

A patient is diagnosed with a disease caused by a protozoan. Which of the following is a defining characteristic of protozoa?

Accepted Answer

They are unicellular eukaryotes that often move by cilia, flagella, or pseudopodia.

Question 20

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

Accepted Answer

It amplifies specific DNA sequences of the pathogen using polymerase chain reaction (PCR).

Exam 3: Microbiology Study Guide: Classification, Pathogenicity, and Disease

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