Question 1

Which of the following best describes the difference between pathogenicity and virulence?

Accepted Answer

Pathogenicity is the ability to cause disease, while virulence is the degree of pathogenicity.

Question 2

A patient develops pneumonia after inhaling droplets containing Streptococcus pneumoniae. Which portal of entry did the pathogen most likely use?

Accepted Answer

Mucous membranes of the respiratory tract

Question 3

Which of the following is the most accurate definition of $$ID_{50}$$?

Accepted Answer

$$ID_{50} is $$the infectious dose required to infect 50\% of a sample population.

Question 4

A patient receives a deep puncture wound from a rusty nail and later develops tetanus. Which portal of entry and mechanism best explain this infection?

Accepted Answer

Parenteral route; direct deposition of Clostridium tetani into tissues

Question 5

Which of the following is a correct statement about bacterial adherence to host tissues?

Accepted Answer

Fimbriae on Actinomyces allow adherence to the glycocalyx of Streptococcus mutans.

Question 6

Which bacterial structure is most directly responsible for resisting phagocytosis in Streptococcus pneumoniae?

Accepted Answer

Capsule (glycocalyx) around the cell wall

Question 7

A strain of Neisseria gonorrhoeae is able to attach to host cells and evade immune detection by frequently changing its surface proteins. Which two mechanisms are being used?

Accepted Answer

Opa protein for attachment and antigenic variation for immune evasion

Question 8

Which enzyme produced by bacteria allows them to break down host connective tissue and spread through the body?

Accepted Answer

Collagenase

Question 9

A patient is infected with a bacterium that produces an A-B exotoxin. Which of the following best describes the mechanism of this toxin?

Accepted Answer

The B component binds to the host cell, allowing the A component to enter and disrupt cellular function.

Question 10

Which of the following statements about endotoxins is correct?

Accepted Answer

Endotoxins are part of the Lipid A portion of lipopolysaccharides (LPS) in gram-negative bacteria.

Question 11

A laboratory is testing a new batch of intravenous fluids for contamination. Which assay would be most appropriate to detect the presence of bacterial endotoxins?

Accepted Answer

Limulus amebocyte lysate (LAL) assay

Question 12

Which of the following best explains why biofilms are difficult to eradicate in chronic infections?

Accepted Answer

Biofilm bacteria are shielded by extracellular polymeric substances (EPS), making them more resistant to phagocytosis and antibiotics.

Question 13

A patient develops symptoms of fever, shock, and a drop in blood pressure after a gram-negative bacterial infection. Which mechanism is most likely responsible?

Accepted Answer

Release of endotoxins (Lipid A) during bacterial lysis

Question 14

Which of the following is a real-world example of antigenic variation that complicates vaccine development?

Accepted Answer

Influenza virus changing its surface antigens each season

Question 15

Which of the following statements about siderophores is correct?

Accepted Answer

Siderophores are proteins secreted by bacteria to bind iron more tightly than host iron-binding proteins.

Question 16

A patient is diagnosed with paralytic shellfish poisoning after eating contaminated shellfish. Which microbial product is responsible for this condition?

Accepted Answer

Saxitoxin produced by dinoflagellates

Question 17

Which of the following is a cytopathic effect (CPE) of viral infection that can lead to cancer?

Accepted Answer

Transformation of host cells resulting in loss of contact inhibition

Question 18

A patient with a chronic fungal infection is found to have a capsule surrounding the fungal cells. What is the most likely function of this capsule?

Accepted Answer

To prevent phagocytosis by host immune cells

Question 19

Which of the following best explains why some bacteria can survive inside phagocytes?

Accepted Answer

They can escape from the phagosome before lysosomal fusion or prevent fusion of lysosome with phagosome.

Question 20

A patient is infected with a bacterium that produces a superantigen. Which of the following symptoms is most likely to occur due to the action of this toxin?

Accepted Answer

Fever, shock, and potentially death due to massive cytokine release

Microbial Mechanisms of Pathogenicity (Chapter 15) - Study Notes

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