Q: Which of the following equations correctly represents the calculation of colony-forming units per milliliter (CFU/mL) when 0.1 mL of a 1:1000 dilution yields 50 colonies on an agar plate?

$$CFU/mL = \frac{50}{0.1} \times 1000$$

Question 1

Which of the following best describes the difference between mechanical and biological vectors in the transmission of infectious diseases?

Accepted Answer

Mechanical vectors passively carry pathogens on their body surfaces, while biological vectors are required for the pathogen to complete part of its life cycle.

Question 2

A patient develops symptoms of a disease after being bitten by a mosquito. The mosquito is required for the pathogen to mature before transmission. What type of vector is the mosquito in this scenario?

Accepted Answer

Biological vector

Question 3

Which of the following is NOT a function of inflammation in the immune response?

Accepted Answer

To directly produce antibodies against pathogens

Question 4

During the process of phagocytosis, which step involves the fusion of the phagosome with lysosomes to form a phagolysosome?

Accepted Answer

Digestion

Question 5

A patient is diagnosed with a bacterial infection. Which of the following best describes the role of neutrophils in the innate immune response?

Accepted Answer

They engulf and destroy bacteria through phagocytosis.

Question 6

Which of the following equations correctly represents the calculation of colony-forming units per milliliter (CFU/mL) when 0.1 mL of a 1:1000 dilution yields 50 colonies on an agar plate?

Accepted Answer

$$CFU/mL = \frac{50}{0.1} 	imes 1000$$

Question 7

Which of the following best describes the difference between the primary and secondary immune responses?

Accepted Answer

The secondary response involves memory cells and is more rapid and robust than the primary response.

Question 8

A patient receives a vaccine containing inactivated (killed) virus particles. Which type of immunity is being induced?

Accepted Answer

Artificial active immunity

Question 9

Which of the following is a correct sequence of events in the stages of infection?

Accepted Answer

Incubation period → Prodromal stage → Invasion period → Convalescent period

Question 10

Which of the following statements about the complement system is TRUE?

Accepted Answer

The complement system can be activated by three different pathways.

Question 11

A laboratory technician needs to determine the minimum inhibitory concentration (MIC) of an antibiotic. Which of the following best describes the MIC?

Accepted Answer

The lowest concentration of antibiotic that inhibits visible bacterial growth.

Question 12

Which of the following best describes the role of dendritic cells in the immune system?

Accepted Answer

They phagocytose pathogens and present antigens to T cells, initiating the adaptive immune response.

Question 13

A patient is exposed to a pathogen and develops disease symptoms after a few days. Which phase of the disease process is the patient most likely experiencing?

Accepted Answer

Invasion period

Question 14

Which of the following is a characteristic of the adaptive immune response but NOT the innate immune response?

Accepted Answer

Memory of previous encounters with specific pathogens

Question 15

Which of the following best describes the function of eosinophils in the immune system?

Accepted Answer

They are primarily involved in the destruction of parasitic worms and modulation of allergic inflammatory responses.

Question 16

A patient is given an antitoxin after exposure to a bacterial toxin. What type of immunity is this?

Accepted Answer

Artificial passive immunity

Question 17

Which of the following best explains why Gram-negative bacteria are often more resistant to antibiotics than Gram-positive bacteria?

Accepted Answer

Gram-negative bacteria possess an outer membrane that restricts entry of many antibiotics.

Question 18

Which of the following is a correct description of herd immunity?

Accepted Answer

It is the protection of susceptible individuals in a population when a sufficient proportion is immune.

Question 19

Which of the following best describes the role of the thymus in the immune system?

Accepted Answer

It is the site of T cell maturation.

Question 20

A patient with a genetic deficiency in complement protein C3 is likely to experience which of the following?

Accepted Answer

Decreased ability to opsonize pathogens and increased susceptibility to infections

Unit 3 Study Guide: Pathogenesis, Immunity, and Laboratory Techniques in Microbiology

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