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 is exposed to Bacillus anthracis through a cut in the skin. Which portal of entry is being utilized?

Accepted Answer

Parenteral route

Question 3

The infectious dose for 50% of a sample population is known as:

Accepted Answer

$$ID_{50}$$

Question 4

Which structure allows Streptococcus pneumoniae to evade phagocytosis?

Accepted Answer

Capsule (glycocalyx)

Question 5

A patient develops a fever after being infected with a gram-negative bacterium. Which component is most likely responsible for this symptom?

Accepted Answer

Lipid A of lipopolysaccharide (endotoxin)

Question 6

Which enzyme produced by bacteria digests polysaccharides that hold cells together, facilitating tissue invasion?

Accepted Answer

Hyaluronidase

Question 7

A bacterial pathogen alters its surface antigens to evade the host immune response. This process is called:

Accepted Answer

Antigenic variation

Question 8

Which of the following best explains how siderophores contribute to bacterial pathogenicity?

Accepted Answer

They bind iron more tightly than host proteins, allowing bacteria to acquire essential nutrients.

Question 9

Which of the following is a characteristic of exotoxins?

Accepted Answer

They are proteins secreted by bacteria and are often highly specific in their action.

Question 10

A patient presents with symptoms of shock and disseminated intravascular coagulation after a severe gram-negative bacterial infection. Which mechanism is most likely responsible?

Accepted Answer

Release of endotoxins (Lipid A) from lysed bacteria

Question 11

Which of the following best describes the action of A-B exotoxins?

Accepted Answer

The B component binds to the host cell receptor, and the A component exerts the toxic effect inside the cell.

Question 12

Which of the following is a cytopathic effect (CPE) of viral infection?

Accepted Answer

Formation of syncytia (multinucleated giant cells)

Question 13

Aflatoxin, a carcinogenic toxin, is produced by which type of microorganism?

Accepted Answer

Fungi (Aspergillus species)

Question 14

Which of the following is a portal of exit for pathogens from the human body?

Accepted Answer

Respiratory tract via coughing and sneezing

Question 15

A patient develops paralytic shellfish poisoning after eating contaminated seafood. Which microbial product is responsible?

Accepted Answer

Saxitoxin produced by algae

Question 16

Which of the following best explains why biofilms make bacteria more resistant to phagocytosis?

Accepted Answer

The extracellular polymeric substance (EPS) shields bacteria from immune cells.

Question 17

A patient is infected with Neisseria gonorrhoeae, which uses Opa protein to attach to host cells. Which process is being described?

Accepted Answer

Adherence

Question 18

Which of the following is a multi-step process involving rearrangement of actin filaments to allow bacterial entry into host cells?

Accepted Answer

Invasin-mediated membrane ruffling

Question 19

Which of the following statements about superantigens is correct?

Accepted Answer

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

Question 20

A patient is diagnosed with tuberculosis. Which cell wall component of Mycobacterium tuberculosis helps it resist digestion by phagocytes?

Accepted Answer

Waxy lipid (mycolic acid)

Microbial Mechanisms of Pathogenicity: Study Notes

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