Question 1

Which of the following best defines sterilization in microbiology?

Accepted Answer

The elimination of all bacteria, viruses, and endospores from an object or environment.

Question 2

A hospital needs to sterilize heat-sensitive electronic equipment. Which method is most appropriate?

Accepted Answer

Exposure to ethylene oxide gas

Question 3

Which of the following statements about decimal reduction time ($$D$$ value) is correct?

Accepted Answer

It is the time in minutes required to kill 90% of a microbial population at a set temperature.

Question 4

Which physical method is most effective for removing microbes, including viruses, from heat-sensitive liquids?

Accepted Answer

Membrane filtration with pore sizes as small as $$0.01\ \mu\mathrm{m}$$

Question 5

A laboratory is using UV light to disinfect the surfaces of a biosafety cabinet. What is the primary mechanism by which UV light damages microbes?

Accepted Answer

Formation of thymine dimers in DNA

Question 6

Which of the following is a limitation of boiling as a method of microbial control?

Accepted Answer

Endospores can survive boiling for hours.

Question 7

Which chemical agent is classified as a high-level germicide and is effective even in the presence of organic material, leaving no residue?

Accepted Answer

Peracetic acid

Question 8

A nurse is cleaning a stethoscope with 70% ethanol. What level of germicidal activity does this provide?

Accepted Answer

Intermediate-level

Question 9

Which of the following best describes the action of cationic detergents (quaternary ammonium compounds)?

Accepted Answer

They disrupt plasma membranes and are bactericidal but sporostatic.

Question 10

Which control method is most effective for eliminating prions from surgical instruments?

Accepted Answer

A combination of chemical treatments and increased temperature and pressure during autoclaving

Question 11

Which of the following is NOT a factor to consider when selecting an appropriate germicide?

Accepted Answer

Color of the equipment

Question 12

Which of the following statements about HEPA filters is correct?

Accepted Answer

They remove 99.97% of airborne substances with pore sizes of $$0.3\ \mu\mathrm{m} or $$larger.

Question 13

Which of the following best describes the difference between disinfectants and antiseptics?

Accepted Answer

Disinfectants are used on inanimate objects, while antiseptics are used on living tissue.

Question 14

A microbiologist needs to sterilize a glass flask containing culture media. Which method is most appropriate?

Accepted Answer

Autoclaving at $$121\ ^\circ \mathrm{C}$$, 15 psi for 20 minutes

Question 15

Which of the following is a correct statement about the control of Mycobacterium species?

Accepted Answer

Their cell walls contain waxy mycolic acids, making them resistant to many control measures.

Question 16

Which of the following is the best explanation for why a can of pork takes longer to sterilize than a can of soup containing pieces of pork?

Accepted Answer

Solid pieces of pork conduct heat less efficiently than liquid, requiring more time for sterilization.

Question 17

Which of the following is a property of ionizing radiation used for microbial control?

Accepted Answer

It generates reactive ions that damage nucleic acids and can pass through packaging.

Question 18

Which of the following is a reason why chlorine bleach may be less effective in some situations?

Accepted Answer

It is rapidly inactivated by organic material.

Question 19

Which of the following best describes the action of phenolic compounds in microbial control?

Accepted Answer

They disrupt bacterial cell walls and interact with proteins.

Controlling Microbial Growth: Physical and Chemical Methods

Study Guide - Practice Questions