Question 1

Which enzyme produced by Helicobacter pylori allows it to survive in the acidic environment of the stomach by neutralizing gastric acid?

Accepted Answer

Urease

Question 2

A strain of Vibrio cholerae loses its fimbriae due to a mutation. Which function is most directly impaired?

Accepted Answer

The ability to bind to a host target cell.

Question 3

Which of the following enzymes is responsible for dissolving fibrin clots, allowing Staphylococcus aureus to spread through tissues?

Accepted Answer

Staphylokinase

Question 4

What is the primary advantage for a bacterium to invade and reside inside host cells?

Accepted Answer

The bacteria can hide and be protected from antibodies and immune cells.

Question 5

Which enzyme is most likely to be produced by bacteria to degrade the extracellular matrix and facilitate tissue penetration?

Accepted Answer

Hyaluronidase

Question 6

Gram-negative Haemophilus influenzae requires heme for growth because:

Accepted Answer

It needs heme to bind iron for transport and acquisition in the cell.

Question 7

Which of the following best describes the function of bacterial siderophores?

Accepted Answer

They chelate iron from host proteins and transport it into the bacterial cell.

Question 8

A mutation in Shigella flexneri prevents production of pore-forming toxins. What is the most likely consequence?

Accepted Answer

The bacterium loses the ability to escape the phagosome and enter the cytosol.

Question 9

Which of the following is a key factor in the formation of a comedone (blackhead or whitehead) in acne?

Accepted Answer

Accumulation of sebum and dead skin cells plugging the follicle.

Question 10

Brucella abortus grows rapidly in the placenta due to the presence of which nutrient?

Accepted Answer

Erythritol

Question 11

Which bacterial enzyme is most likely to degrade DNA in pus, reducing its viscosity and aiding bacterial dissemination?

Accepted Answer

DNase

Question 12

Listeria monocytogenes escapes from the phagosome into the cytosol by producing which type of toxin?

Accepted Answer

Pore-forming and membrane-degrading toxins

Question 13

Which of the following pathogens is known for using actin-based motility to spread from cell to cell without exposure to the humoral immune system?

Accepted Answer

Listeria monocytogenes

Question 14

Which of the following equations best represents the reaction catalyzed by urease in Helicobacter pylori?

Accepted Answer

$$\mathrm{(NH_2$)_2CO + H_2O \rightarrow 2NH_3 + CO_2$}$$

Question 15

Which of the following is NOT a mechanism used by bacteria to acquire iron from the host?

Accepted Answer

Direct uptake of free iron from the bloodstream

Question 16

Salmonella enterica survives inside host cells by preventing which cellular process?

Accepted Answer

Fusion of the phagosome with the lysosome

Question 17

Which of the following best describes the role of hyaluronidase in bacterial pathogenesis?

Accepted Answer

Degrades hyaluronic acid in connective tissue, facilitating bacterial spread.

Question 18

Which of the following pathogens is classified as an obligate intracellular bacterium and has both infectious and metabolically active forms?

Accepted Answer

Chlamydia

Question 19

Which of the following is a plausible consequence of a mutation in Streptococcus species that prevents production of streptokinase?

Accepted Answer

The bacteria would be less able to escape from fibrin clots and disseminate.

Question 20

Which of the following best explains why Borrelia burgdorferi uses Mn2+ instead of Fe2+ for its metabolism?

Accepted Answer

Host iron is tightly sequestered, so Borrelia evolved to use manganese.

lecture 12

Study Guide - Practice Questions