Question 1

Which of the following is NOT a principal portal of entry for microorganisms into the human body?

Accepted Answer

Intact skin

Question 2

A researcher is comparing two bacterial toxins. Toxin A has an $$LD_{50} of 0.1 mg/kg$$, while Toxin B has an $$LD_{50} of 10 mg/kg. $$Which statement is correct?

Accepted Answer

Toxin A is more potent than Toxin B.

Question 3

Which of the following best describes the role of adhesins in microbial pathogenicity?

Accepted Answer

They allow pathogens to bind to specific host cell receptors.

Question 4

A patient develops pneumonia caused by Streptococcus pneumoniae. Which virulence factor most likely helps this bacterium evade phagocytosis?

Accepted Answer

Capsule

Question 5

Which enzyme produced by bacteria is responsible for breaking down the polysaccharides that hold host cells together, facilitating tissue invasion?

Accepted Answer

Hyaluronidase

Question 6

Antigenic variation allows pathogens to:

Accepted Answer

Change their surface proteins to evade the host immune system

Question 7

Which of the following statements about siderophores is TRUE?

Accepted Answer

They bind iron more tightly than host iron-binding proteins.

Question 8

Which of the following is an example of direct damage caused by a pathogen?

Accepted Answer

Disruption of host cell function by viral replication

Question 9

Which of the following best distinguishes exotoxins from endotoxins?

Accepted Answer

Exotoxins are proteins secreted by living bacteria; endotoxins are lipid A components of the outer membrane of gram-negative bacteria.

Question 10

A-B exotoxins act by:

Accepted Answer

Binding to host cell receptors and inhibiting protein synthesis inside the cell

Question 11

Which of the following is a cytopathic effect of viral infection?

Accepted Answer

Formation of a syncytium

Question 12

Which of the following is a property of endotoxins but NOT exotoxins?

Accepted Answer

Cause fever by inducing cytokine release

Question 13

A patient develops symptoms after eating shellfish contaminated with a neurotoxin produced by algae. This is an example of:

Accepted Answer

Paralytic shellfish poisoning caused by saxitoxin

Question 14

Which of the following best describes the mechanism of action of superantigens?

Accepted Answer

They cause an intense immune response by stimulating massive cytokine release from T cells.

Question 15

Which of the following is a portal of exit for pathogens that is also a portal of entry?

Accepted Answer

Respiratory tract

Question 16

A bacterial strain acquires the ability to produce a toxin after infection by a bacteriophage. This is an example of:

Accepted Answer

Lysogenic conversion

Question 17

Which of the following is a function of bacterial coagulases?

Accepted Answer

Coagulate fibrinogen to form clots

Question 18

A patient is infected with Mycobacterium tuberculosis. Which cell wall component helps this bacterium resist digestion by phagocytes?

Accepted Answer

Mycolic acid

Question 19

Which of the following is a real-life example of a disease caused by a membrane-disrupting exotoxin?

Accepted Answer

Streptolysin-induced hemolysis in Streptococcus pyogenes infections

Question 20

Which of the following best explains why handwashing reduces the risk of infection?

Accepted Answer

It decreases the number of invading microbes, lowering the chance of reaching the $$ID_{50}.$$

Microbial Mechanisms of Pathogenicity: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards