$$\text{Plasminogen} + \text{Streptokinase} \rightarrow \text{Plasmin}$$

Question 1

Which of the following is the correct sequence of steps in bacterial pathogenesis leading to tissue damage and disease?

Accepted Answer

Reservoirs → Transmission → Entry to host's body → Adhesion to host's tissue → Invasion: colonization and growth → Production of toxins

Question 2

Yersinia species utilize which mechanism to invade non-phagocytic host cells?

Accepted Answer

Binding and focussing of host membrane proteins, leading to actin-polymerization and subsequent phagocytosis

Question 3

Which virulence factor is secreted by Salmonella to manipulate host cell cytoskeleton during invasion?

Accepted Answer

SopE

Question 4

What is the primary function of hyaluronidase produced by Streptococci and Staphylococci during infection?

Accepted Answer

Attacks the interstitial cement by depolymerizing hyaluronic acid

Question 5

Listeria monocytogenes spreads from cell to cell by which process?

Accepted Answer

Actin-polymerization at one pole, propelling the bacterium through the cytoplasm and into adjacent cells

Question 6

Which equation best represents the conversion of plasminogen to plasmin by streptokinase?

Accepted Answer

$$	ext{Plasminogen} + 	ext{Streptokinase} ightarrow 	ext{Plasmin}$$

Question 7

A patient infected with Streptococcus pyogenes is found to have bacteria evading antibody binding. Which protein is most likely responsible?

Accepted Answer

M protein

Question 8

Which of the following mechanisms allows bacteria to evade phagocytosis by the host immune system?

Accepted Answer

Presence of a capsule containing sialic acid and hyaluronic acid

Question 9

During Salmonella infection, which process restores the host cell cytoskeleton and allows bacterial multiplication within the phagosome?

Accepted Answer

Restoration of an intact cytoskeleton

Question 10

Which spreading factor is responsible for breaking down collagen, facilitating gas gangrene?

Accepted Answer

Collagenase

Question 11

A mutation in the gene encoding Listeriolysin O in Listeria monocytogenes would most likely result in which effect?

Accepted Answer

Inability to escape from the phagosome into the cytoplasm

Question 12

Which of the following is a direct consequence of the production of spreading factors by bacteria?

Accepted Answer

Invasion into deeper tissues

Question 13

Staphylococcus aureus evades the immune system by binding to which host protein?

Accepted Answer

Collagen

Question 14

Which process is illustrated by the equation below?
$$	ext{Hyaluronic acid} + 	ext{Hyaluronidase} ightarrow 	ext{Disaccharides}$$

Accepted Answer

Degradation of interstitial cement for tissue invasion

Question 15

Which bacterial species is most associated with actin-polymerization-driven intracellular motility and cell-to-cell spread?

Accepted Answer

Listeria monocytogenes

Question 16

What is the role of SopE in Salmonella infection?

Accepted Answer

Activates small GTP-binding protein CDC42, leading to cytoskeletal rearrangement

Question 17

Which host cell receptor does Yersinia invasin bind to during the initial stages of infection?

Accepted Answer

Alpha-beta integrins ($$\alpha_\beta-$$integrins)

Question 18

A bacterial capsule containing sialic acid and hyaluronic acid helps evade the immune system by:

Accepted Answer

Preventing antibody formation against the capsule

Question 19

Which of the following best describes the function of M protein in Streptococcus pyogenes?

Accepted Answer

Binds host fibrinogen, providing protection from antibody binding

Question 20

During the dissemination of Listeria monocytogenes, which event is critical for movement into adjacent epithelial cells?

Accepted Answer

Actin-polymerization at one pole and lysis of the phagosomal membrane by Listeriolysin O

Bacterial Pathogenesis: Mechanisms of Invasion and Immune Evasion

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