Question 1

Which of the following best distinguishes a virus from a bacterium?

Accepted Answer

Viruses lack ribosomes and metabolic enzymes, while bacteria possess both.

Question 2

A researcher is culturing animal viruses and needs a cell line that can be maintained indefinitely for repeated experiments. Which type of cell line should they use, and why?

Accepted Answer

Continuous cell lines, because they can be subcultured indefinitely.

Question 3

Which of the following best describes the difference between a latent and a persistent viral infection?

Accepted Answer

Latent infections remain dormant and can reactivate, while persistent infections involve continuous viral replication.

Question 4

A patient develops fever and chills after cardiac catheterization, but the water and catheters used were sterile. Which test should have been performed to detect the likely cause of these symptoms?

Accepted Answer

The Limulus Amebocyte Lysate (LAL) assay to detect endotoxins.

Question 5

Which of the following statements about Koch’s postulates is correct?

Accepted Answer

Some pathogens cannot be cultured in artificial media, making exceptions to Koch’s postulates necessary.

Question 6

A bacterial toxin has an $$LD_{50} of$$ $$0.03\ \mathrm{ng/kg}$$, while another has an $$LD_{50} of$$ $$12\ \mathrm{mg/kg}. $$Which statement is correct?

Accepted Answer

The toxin with $$LD_{50} = 0.03\ \mathrm{ng/kg} is $$more potent.

Question 7

Which of the following best explains why the influenza vaccine must be updated annually?

Accepted Answer

Influenza viruses undergo antigenic variation, changing their surface proteins.

Question 8

Which of the following is a function shared by both capsules and M proteins in bacterial pathogenicity?

Accepted Answer

They help bacteria evade phagocytosis by host immune cells.

Question 9

A patient is diagnosed with listeriosis, and the causative agent is found to survive inside phagocytes. Which mechanism does Listeria monocytogenes use to avoid destruction?

Accepted Answer

It escapes from the phagosome into the cytoplasm before lysosomal fusion.

Question 10

Which of the following best describes the action of A-B toxins?

Accepted Answer

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

Question 11

Which of the following is a real-world example of vehicle transmission of disease?

Accepted Answer

A person contracts cholera after drinking contaminated water.

Question 12

Which of the following best defines herd immunity?

Accepted Answer

When a high percentage of a population is immune, the spread of disease is limited.

Question 13

Which of the following is a function of siderophores in bacterial infections?

Accepted Answer

They bind and sequester iron from the host, aiding bacterial growth.

Question 14

Which of the following is a correct sequence in the pattern of disease progression?

Accepted Answer

Incubation period, prodromal period, period of illness, period of decline, period of convalescence

Question 15

Which of the following best describes the role of Toll-like receptors (TLRs) in innate immunity?

Accepted Answer

They recognize pathogen-associated molecular patterns (PAMPs) and activate immune responses.

Question 16

A patient is given an injection of gamma globulin after exposure to hepatitis A. Which type of adaptive immunity is this?

Accepted Answer

Artificially acquired passive immunity

Question 17

Which class of antibody is most likely to protect you from a common cold virus at the mucosal surface?

Accepted Answer

IgA

Question 18

Which of the following best describes the function of natural killer (NK) cells?

Accepted Answer

They destroy cells that lack MHC class I molecules on their surface.

Question 19

Which of the following is a correct statement about the complement system?

Accepted Answer

It can be activated by the classical, alternative, or lectin pathways.

Question 20

A patient is exposed to a pathogen for the first time and develops a slow, low-level antibody response. Upon a second exposure, the response is faster and stronger. What is this phenomenon called?

Accepted Answer

Anamnestic (secondary) immune response

Microbiology Study Guide: Step-by-Step Guidance for Key Concepts

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