Question 1

Which of the following best describes the main difference between Gram-positive and Gram-negative bacteria as revealed by Gram staining?

Accepted Answer

Gram-positive bacteria stain violet due to a thick peptidoglycan layer, while Gram-negative bacteria stain pink due to a thinner peptidoglycan layer and an outer membrane.

Question 2

A patient is diagnosed with a bacterial infection caused by a rod-shaped, Gram-negative organism. Which of the following is the most likely classification of this bacterium?

Accepted Answer

Bacillus (bacilli)

Question 3

Which of the following statements about bacterial reproduction is correct?

Accepted Answer

Bacteria reproduce asexually by binary fission, where the cell elongates, replicates its DNA, and divides into two identical cells.

Question 4

Which of the following best explains why normal gut flora are considered symbiotic?

Accepted Answer

They obtain nutrients from the host and help compete with pathogenic microbes, benefiting both the host and the microbes.

Question 5

A laboratory technician observes a bacterium that stains pink with Gram stain and is rod-shaped. Which of the following best describes this organism?

Accepted Answer

Gram-negative bacillus

Question 6

Which of the following is a key factor that increases the virulence of a pathogen?

Accepted Answer

The ability to disable the host's defense systems

Question 7

Which of the following best describes the structure of a virus?

Accepted Answer

A nucleic acid (DNA or RNA) enclosed in a protein capsid, sometimes with an additional envelope

Question 8

A patient presents with a fungal infection of the skin and nails. Which term best describes this type of infection?

Accepted Answer

Superficial mycosis

Question 9

Which of the following is a characteristic of prokaryotic cells?

Accepted Answer

They lack a defined nucleus.

Question 10

Which of the following best explains why Gram-negative bacteria are often more resistant to antibiotics than Gram-positive bacteria?

Accepted Answer

They possess an outer membrane that acts as a barrier to many antibiotics.

Question 11

A patient is diagnosed with an infection caused by Enterobius vermicularis. Which type of organism is responsible for this infection?

Accepted Answer

Helminth (pinworm)

Question 12

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

The cell elongates, replicates its DNA, forms a cross-wall, and divides into two identical cells.

Question 13

Which of the following is an example of an arthropod that can cause infection in humans?

Accepted Answer

Tick

Question 14

Which of the following best describes an endotoxin?

Accepted Answer

A toxin that is part of the organism's cell membrane and released when the cell is destroyed

Question 15

A patient develops a systemic fungal infection after inhaling spores. Which of the following best describes the route of infection?

Accepted Answer

Inhalation leading to systemic mycosis

Question 16

Which of the following is a key step in breaking the chain of transmission of infectious diseases?

Accepted Answer

Interrupting the mode of transmission, such as through hand hygiene or sterilization

Question 17

Which of the following best describes the difference between colonization and infection?

Accepted Answer

Colonization refers to the presence of microorganisms without causing disease, while infection involves damage and disease.

Question 18

Which of the following best explains why opportunistic infections occur?

Accepted Answer

They occur when symbiotic microbes breach barriers or when host defenses are compromised.

Question 19

A patient is infected with a protozoan that uses the host to reproduce through a complex life cycle. Which of the following organisms is most likely responsible?

Accepted Answer

Giardia

Question 20

Which of the following equations best represents the exponential growth of bacteria during binary fission, where $$N is $$the number of bacteria after $$n$$ generations and $$N_0 is $$the initial number of bacteria?

Accepted Answer

$$N = N_0$ 	imes 2^n$$

Cells and Infection: Microbial Classification and Pathogenicity

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