Q: A laboratory technician is asked to calculate the colony forming units per milliliter (CFU/mL) in a urine sample. If 0.01 mL of urine is plated and 150 colonies are counted, what is the CFU/mL?

$$150 \\div 0.01 = 15,000$$ CFU/mL

Question 1

Which of the following best defines the term 'epidemic' as used in epidemiology?

Accepted Answer

A disease that occurs in higher than expected numbers in a given population over a short period of time.

Question 2

A patient develops a urinary tract infection (UTI) after a hospital stay. Which of the following best describes the most likely source of this infection?

Accepted Answer

A nosocomial infection acquired from the healthcare environment.

Question 3

Which of the following is an example of a biological vector in the transmission of infectious diseases?

Accepted Answer

A mosquito transmitting malaria.

Question 4

Which of the following best describes the function of lysozyme in the innate immune system?

Accepted Answer

It digests peptidoglycan in bacterial cell walls, leading to cell lysis.

Question 5

A laboratory technician is asked to calculate the colony forming units per milliliter (CFU/mL) in a urine sample. If 0.01 mL of urine is plated and 150 colonies are counted, what is the CFU/mL?

Accepted Answer

$$150 \div 0.01 = 15,000$$ CFU/mL

Question 6

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

Accepted Answer

To prevent the migration of immune cells to the site of infection.

Question 7

A patient presents with fever, malaise, and a high neutrophil count. Which stage of infectious disease is most likely occurring?

Accepted Answer

Acute phase

Question 8

Which of the following statements about Koch's postulates is correct?

Accepted Answer

They require that the suspected pathogen be isolated and grown in pure culture.

Question 9

Which of the following best describes the role of MHC class I molecules in the immune response?

Accepted Answer

They present endogenous antigens to cytotoxic T cells.

Question 10

A patient is suspected of having bacterial meningitis. Which laboratory finding would best support this diagnosis compared to viral (aseptic) meningitis?

Accepted Answer

Cerebrospinal fluid (CSF) with high protein and low glucose levels.

Question 11

Which of the following is a correct statement about the complement system?

Accepted Answer

It can be activated by three pathways: classical, alternative, and lectin.

Question 12

Which of the following is an example of a non-specific (innate) chemical defense against pathogens?

Accepted Answer

Lysozyme in tears and saliva

Question 13

A patient receives a flu vaccine containing inactivated virus. Which type of immunity is being induced?

Accepted Answer

Artificial active immunity

Question 14

Which of the following best describes the function of chemotaxis in the inflammatory response?

Accepted Answer

It directs the movement of immune cells toward the site of infection.

Question 15

Which of the following is a correct statement about the acute phase of an infectious disease?

Accepted Answer

The pathogen is multiplying at its highest rate and symptoms are most severe.

Question 16

A blood culture is performed to diagnose a bloodstream infection. Which of the following is a critical consideration to avoid contamination?

Accepted Answer

Using a sterile technique when collecting the specimen.

Question 17

Which of the following best describes the difference between the primary and secondary immune response to an antigen?

Accepted Answer

The secondary response is faster and produces more antibodies due to memory cells.

Question 18

Which of the following is a correct statement about direct ELISA?

Accepted Answer

It detects the presence of antigen using a labeled antibody.

Question 19

Which of the following is a characteristic of a subunit vaccine?

Accepted Answer

It contains only specific antigens from the pathogen, not the whole organism.

Question 20

A patient is exposed to a pathogen but does not develop disease due to the action of ciliary escalator and mucous membranes. Which type of innate immunity barrier is responsible?

Accepted Answer

Physical barrier

Microbiology Study Guide: Epidemiology, Immunity, and Laboratory Diagnosis

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