Q: Which equation best represents the calculation of infectious dose 50 ($$ID_{50}$$), the dose at which 50% of exposed hosts become infected?

$$ID_{50} is $$the dose at which $$P(\text{infection}) = 0.5$$

Question 1

Which of the following best describes the concept of 'balanced pathogenicity' in host-pathogen interactions?

Accepted Answer

A pathogen maintains a level of virulence that allows it to replicate and spread without killing the host too quickly.

Question 2

Which phase of infectious disease is characterized by the most evident signs and symptoms?

Accepted Answer

Illness

Question 3

A patient presents with fever and chills, and blood cultures reveal the presence of bacteria. Which term best describes this condition?

Accepted Answer

Bacteremia

Question 4

Which of the following is a major reason why pathogens must out-compete native flora to colonize successfully?

Accepted Answer

Native flora occupy niches and resources, preventing pathogen establishment.

Question 5

Which virulence factor allows Neisseria meningitidis to avoid complement activation?

Accepted Answer

Factor H binding protein

Question 6

A researcher disrupts a gene in a virulent bacterial strain and observes reduced virulence. Which molecular Koch's postulate does this experiment demonstrate?

Accepted Answer

Disruption of the gene in a virulent strain should reduce virulence.

Question 7

Which of the following mechanisms is used by extracellular pathogens to avoid phagocytosis?

Accepted Answer

Production of C5a peptidase to prevent PMN recruitment

Question 8

A bacterial strain acquires a pathogenicity island (PAI) through horizontal gene transfer. What is the most likely outcome?

Accepted Answer

The bacterium gains new virulence factors and may become pathogenic.

Question 9

Which of the following best explains why some pathogens are better off being phagocytosed quickly by macrophages before activation?

Accepted Answer

Activated macrophages have enhanced oxidative and digestive capabilities, making survival more difficult for pathogens.

Question 10

Which of the following is a real-world example of a pathogen using actin 'rockets' to spread within host cells?

Accepted Answer

Listeria monocytogenes moving through epithelial cells

Question 11

Which equation best represents the calculation of infectious dose 50 ($$ID_{50}$$), the dose at which 50% of exposed hosts become infected?

Accepted Answer

$$ID_{50} is $$the dose at which $$P(	ext{infection}) = 0.5$$

Question 12

Which of the following is NOT an exception to Koch's postulates?

Accepted Answer

Diseases caused by a single, easily cultured organism

Question 13

Which virulence factor allows Staphylococcus aureus to avoid the immune system by binding the Fc region of antibodies?

Accepted Answer

Staphylococcal protein A

Question 14

A patient develops a disseminated infection that spreads throughout the body. Which term best describes this type of infection?

Accepted Answer

Systemic infection

Question 15

Which of the following is a function of IgA protease produced by some bacteria?

Accepted Answer

Destroys mucosal antibody IgA to evade immune detection

Question 16

Which process allows bacteria to adhere to specific cell types, such as urinary tract or intestinal epithelium?

Accepted Answer

Fimbrial adhesins binding to host cell receptors

Question 17

Which of the following best describes the role of M cells in mucosal-associated lymphoid tissue (MALT)?

Accepted Answer

They uptake materials from the lumen to present to dendritic cells and macrophages.

Question 18

Which of the following is a mechanism by which Salmonella survives inside host cells?

Accepted Answer

Prevents fusion of phagosome and lysosome

Question 19

Which of the following is a consequence of disrupting native flora in the human body?

Accepted Answer

Increased risk of autoimmune diseases such as diabetes and asthma

Question 20

A bacterium uses a Type III secretion system to inject effectors into host epithelial cells. What is the primary result of this interaction?

Accepted Answer

Rearrangement of the host cell cytoskeleton to facilitate bacterial uptake

Host-Pathogen Interactions: Receptors, Adhesins, and Pathogenicity

Guida di studio - Domande di pratica

Study guide - Flashcard