Question 1

Which of the following best explains why viruses are not considered living organisms?

Accepted Answer

They can only reproduce inside a host cell and lack their own metabolism.

Question 2

A patient receives a blood transfusion and develops a severe reaction. Which type of hypersensitivity is most likely responsible, and what is the underlying mechanism?

Accepted Answer

Type II (Cytotoxic); antibodies target and destroy transfused red blood cells.

Question 3

Which of the following statements about prions is correct?

Accepted Answer

Prions are infectious proteins that cause disease by inducing abnormal folding of normal brain proteins.

Question 4

A newborn is exposed to microbes during birth and feeding. This process is best described as:

Accepted Answer

Acquisition of normal microbiota, which helps establish the resident microbial community.

Question 5

Which antibody is the most abundant in blood and is the only one that can cross the placenta to protect a fetus?

Accepted Answer

IgG

Question 6

A patient presents with a 'bull’s-eye' rash after a tick bite. Which disease is most likely, and what is the vector?

Accepted Answer

Lyme Disease; deer tick

Question 7

Which of the following best describes the mechanism of action for the first line of immune defense?

Accepted Answer

Physical and chemical barriers such as skin and lysozyme prevent pathogen entry.

Question 8

A patient with HIV is diagnosed with AIDS when which of the following occurs?

Accepted Answer

Their Helper T cell (CD4) count drops below 200 or they develop an AIDS-defining infection.

Question 9

Which of the following is a distinguishing feature of viroids compared to viruses?

Accepted Answer

Viroids are small, circular RNA molecules that infect plants and lack a protein coat.

Question 10

A patient develops muscle rigidity and 'lockjaw' after a puncture wound. Which pathogen is responsible, and what is the mechanism?

Accepted Answer

Clostridium tetani; produces a neurotoxin that blocks inhibitory neurotransmitters.

Question 11

Which of the following best explains why tuberculosis is difficult for the immune system to eliminate?

Accepted Answer

The bacterium has a waxy mycolic acid cell wall that resists destruction by immune cells.

Question 12

Which of the following vaccines provides active immunity by exposing the body to a weakened but live form of the pathogen?

Accepted Answer

Attenuated vaccine

Question 13

A patient with peptic ulcers is most likely infected with which microorganism, and what is a common route of transmission?

Accepted Answer

Helicobacter pylori; oral-oral or fecal-oral transmission

Question 14

Which of the following best describes the difference between humoral and cell-mediated immunity?

Accepted Answer

Humoral immunity involves B cells and antibodies, while cell-mediated immunity involves T cells that kill infected cells.

Question 15

A patient develops a thick, gray pseudomembrane in the throat that threatens to block the airway. Which disease is most likely responsible?

Accepted Answer

Diphtheria

Question 16

Which of the following best describes the pathogenesis of malaria?

Accepted Answer

A protozoan parasite destroys red blood cells after being transmitted by a mosquito.

Question 17

A patient is diagnosed with a urinary tract infection (UTI). Which organism is most commonly responsible?

Accepted Answer

Escherichia coli

Question 18

A person develops a severe allergic reaction within minutes of exposure to peanuts, including swelling and difficulty breathing. Which type of hypersensitivity is this, and which antibody is primarily involved?

Accepted Answer

Type I (Immediate); IgE

Question 19

Which of the following sexually transmitted diseases is characterized by four distinct clinical phases?

Accepted Answer

Syphilis

Question 20

A patient presents with flaccid paralysis after eating improperly canned food. Which organism is responsible, and what is the mechanism?

Accepted Answer

Clostridium botulinum; produces a neurotoxin that blocks acetylcholine release at neuromuscular junctions.

Microbiology & Immunology Review: Key Concepts and Clinical Applications

Study Guide - Practice Questions

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