Question 1

Which of the following best defines 'pathogenicity' in microbiology?

Accepted Answer

The ability of a microorganism to cause disease by overcoming host defenses.

Question 2

A researcher is testing a new bacterial strain and finds that 50% of the test population dies after exposure to $$10^3$$ bacteria. What is the LD$$_{50}$$ for this strain?

Accepted Answer

$$10^3$$

Question 3

Which of the following is NOT a typical portal of entry for pathogens?

Accepted Answer

Liver

Question 4

Adhesins are important for bacterial pathogenicity because they:

Accepted Answer

Allow bacteria to bind to specific receptors on host cells.

Question 5

Which of the following bacterial structures is most directly involved in preventing phagocytosis?

Accepted Answer

Capsule

Question 6

A patient is infected with Streptococcus pneumoniae. Which virulence factor is most important for this organism to evade the host immune response?

Accepted Answer

Capsule

Question 7

Which enzyme allows Staphylococcus aureus to clot fibrin and wall off infections from the immune system?

Accepted Answer

Coagulase

Question 8

A bacterial toxin that is inactivated and used in a vaccine is called a:

Accepted Answer

Toxoid

Question 9

Which of the following best describes the action of membrane-disrupting toxins?

Accepted Answer

They lyse host cells by making protein channels in the plasma membrane.

Question 10

A patient develops fever, nausea, vomiting, diarrhea, and shock after a bacterial infection. Which type of toxin is most likely responsible for these symptoms?

Accepted Answer

Superantigen

Question 11

Which of the following statements about endotoxins is TRUE?

Accepted Answer

Endotoxins are heat resistant and can cause fever.

Question 12

Which fungal property allows it to evade phagocytosis and cause persistent infections?

Accepted Answer

Capsule formation

Question 13

A patient presents with symptoms after ingesting shellfish. Which type of microorganism is most likely responsible?

Accepted Answer

Algae

Question 14

Which of the following is a portal of exit for pathogens?

Accepted Answer

Coughing and sneezing

Question 15

A protozoan parasite avoids host defenses by changing its surface antigens. This process is known as:

Accepted Answer

Antigenic variation

Question 16

Which of the following enzymes allows bacteria to hydrolyze hyaluronic acid in connective tissue, facilitating the spread of infection?

Accepted Answer

Hyaluronidase

Question 17

A patient is diagnosed with tuberculosis. Which cell wall component is most important for the virulence of Mycobacterium tuberculosis?

Accepted Answer

Mycolic acid

Question 18

Which of the following is a property of exotoxins?

Accepted Answer

They are proteins that can be inactivated to form toxoids.

Question 19

A patient is infected with Neisseria gonorrhoeae. Which enzyme produced by this bacterium helps it evade the host immune system by destroying antibodies?

Accepted Answer

IgA protease

Question 20

A patient is exposed to a pathogen through a needle stick. Which portal of entry does this represent?

Accepted Answer

Parenteral route

Microbial Pathogenicity and Mechanisms of Disease

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