Question 1

Which of the following best explains why naked (non-enveloped) viruses cannot enter host cells via membrane fusion?

Accepted Answer

They lack a lipid envelope required to merge with the host cell membrane.

Question 2

A patient is prescribed a proton pump inhibitor (PPI) for chronic heartburn. Which of the following best describes the increased risk associated with this medication?

Accepted Answer

Increased risk of gastrointestinal infection due to reduced stomach acidity.

Question 3

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that lack nucleic acids and cause diseases such as Creutzfeldt-Jakob disease.

Question 4

A laboratory is testing the effectiveness of a new antibiotic using the Kirby-Bauer disk-diffusion method. If the zone of inhibition around the antibiotic disk is large, what does this indicate?

Accepted Answer

The bacteria are highly susceptible to the antibiotic.

Question 5

Which of the following best describes the difference between antigenic drift and antigenic shift in influenza viruses?

Accepted Answer

Antigenic drift involves gradual point mutations, while antigenic shift involves abrupt reassortment of genome segments.

Question 6

A patient with a parasitic worm infection is found to have an elevated count of which leukocyte, and what is the primary function of this cell?

Accepted Answer

Eosinophils; frontline defense against parasites and involvement in allergic inflammation.

Question 7

Which of the following mechanisms allows bacteria to overcome the host's nutritional immunity (iron sequestration)?

Accepted Answer

Production of siderophores that scavenge iron from host proteins.

Question 8

Which of the following best distinguishes a mast cell from a basophil under the microscope?

Accepted Answer

Mast cells are larger, have a round nucleus, many granules, and membrane projections; basophils are smaller, have a lobed nucleus, few granules, and a smooth membrane.

Question 9

A patient receives a blood transfusion and develops a hemolytic reaction. Which type of hypersensitivity is this, and what is the underlying mechanism?

Accepted Answer

Type II (cytotoxic); IgG/IgM antibodies bind to cell-surface antigens, leading to cell destruction.

Question 10

Which of the following is a key difference between B-cell receptors (BCRs) and T-cell receptors (TCRs)?

Accepted Answer

BCRs bind free antigen directly, while TCRs only recognize antigen presented on MHC molecules.

Question 11

A patient with HIV is found to have a severely reduced number of CD4+ T cells. What is the primary consequence of this depletion?

Accepted Answer

Impaired coordination of adaptive immunity, leading to increased susceptibility to infections.

Question 12

Which of the following best explains why antigenic shift in influenza viruses can lead to pandemics?

Accepted Answer

It creates viruses with novel surface proteins, potentially allowing infection of new host species and evasion of existing immunity.

Question 13

Which of the following is the correct order of the four stages of the adaptive immune response?

Accepted Answer

Antigen presentation, lymphocyte activation, lymphocyte proliferation and differentiation, antigen elimination and memory.

Question 14

A bacterial strain is resistant to penicillin due to the production of β-lactamase. Which of the following best describes the mechanism of resistance?

Accepted Answer

The enzyme β-lactamase cleaves the β-lactam ring of the antibiotic, inactivating it.

Question 15

A child develops severe allergies after growing up in a highly sanitized environment with little microbial exposure. Which hypothesis best explains this phenomenon?

Accepted Answer

The hygiene hypothesis, which states that reduced early-life microbial exposure increases risk of allergies.

Question 16

Which of the following best describes the action of quinolone antibiotics?

Accepted Answer

They inhibit DNA gyrase/topoisomerase, blocking DNA replication.

Question 17

A patient develops lupus-like symptoms due to deposition of antibody–antigen complexes in tissues. Which type of hypersensitivity is this, and what is the mechanism?

Accepted Answer

Type III (immune complex); immune complexes deposit in tissues causing inflammation.

Question 18

Which of the following is a key feature of T-independent B cell activation?

Accepted Answer

It produces a weaker response with little or no memory and mainly IgM antibodies.

Question 19

A patient is diagnosed with contact dermatitis after exposure to poison ivy. Which type of hypersensitivity is this, and what is the primary immune mechanism?

Accepted Answer

Type IV (delayed); T-cell mediated response.

Microbiology Finals Study Guide: Viruses, Immunity, Immune Disorders, and Antimicrobial Drugs

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