Question 1

Which of the following best describes the process of commercial sterilization in the food industry?

Accepted Answer

A targeted heat treatment that kills Clostridium botulinum endospores in canned goods without compromising food quality.

Question 2

A hospital is preparing surgical instruments for use. Which method would ensure the destruction of all forms of microbial life, including endospores, and what are the standard conditions for this method?

Accepted Answer

Autoclaving at $$121\ ^\circ \mathrm{C}$$ and 15 psi for 15 minutes.

Question 3

Which of the following statements about the logarithmic death curve is correct?

Accepted Answer

It demonstrates that microbial death occurs at a constant rate, with each log decrease representing a 90% reduction in the remaining population.

Question 4

A laboratory technician needs to sterilize a solution containing heat-sensitive enzymes. Which method is most appropriate?

Accepted Answer

Filtration using a membrane filter with pores smaller than $$0.22\ \mu\mathrm{m}.$$

Question 5

Which of the following chemical agents is most effective against bacterial endospores?

Accepted Answer

Glutaraldehyde

Question 6

A patient is treated for a wound infection with an agent that disrupts plasma membranes and is commonly used in surgical hand scrubs. Which agent is most likely being used?

Accepted Answer

Chlorhexidine

Question 7

Which of the following best explains why 100% ethanol is less effective as a disinfectant than 70% ethanol?

Accepted Answer

Water is required to denature proteins effectively, so 70% ethanol is more effective due to its water content.

Question 8

A food manufacturer wants to prevent the germination of Clostridium botulinum endospores in packaged meats. Which additive should be used?

Accepted Answer

Nitrites and nitrates

Question 9

Which of the following physical methods is most effective for sterilizing complex, narrow tubular surgical instruments that cannot withstand high temperatures?

Accepted Answer

Plasma sterilization

Question 10

A researcher is using the disk-diffusion method to evaluate a new disinfectant. What is the primary indicator of the disinfectant's effectiveness in this test?

Accepted Answer

The size of the clear zone of inhibition around the disk.

Question 11

Which of the following statements about ionizing and nonionizing radiation is correct?

Accepted Answer

Ionizing radiation, such as gamma rays, creates hydroxyl radicals that damage DNA, while nonionizing radiation, like UV light, forms thymine dimers in DNA.

Question 12

A nurse wipes a patient's skin with an alcohol swab before giving an injection. This process is best described as:

Accepted Answer

Degerming

Question 13

Which of the following is a limitation of quaternary ammonium compounds (quats) as disinfectants?

Accepted Answer

They are ineffective against endospores and mycobacteria.

Question 14

A microbiologist is comparing the decimal reduction time (DRT) of two bacterial species at $$121\ ^\circ \mathrm{C}. $$Species A has a DRT of 2 minutes, and Species B has a DRT of 5 minutes. If both cultures start with $$10^6$$ cells, how many minutes of exposure are required to reduce each to less than 1 cell?

Accepted Answer

Species A: 12 minutes; Species B: 30 minutes

Question 15

Which of the following best explains why high concentrations of salt or sugar are used to preserve foods?

Accepted Answer

They create a hypertonic environment, causing plasmolysis and inhibiting microbial growth.

Question 16

Which of the following statements about aldehydes as chemical agents is correct?

Accepted Answer

Aldehydes inactivate proteins by forming cross-links with functional groups, making them effective for sterilizing medical equipment.

Question 17

A hospital is considering using gaseous ethylene oxide for sterilizing heat-sensitive medical devices. What is the primary mechanism by which ethylene oxide achieves sterilization?

Accepted Answer

It alkylates proteins and nucleic acids, forming cross-links that inactivate cellular functions.

Question 18

Which of the following is a correct pairing of a chemical agent and its primary use?

Accepted Answer

Silver nitrate – prevention of ophthalmia neonatorum in newborns

Question 19

Why are essential oils generally more effective against gram-positive bacteria than gram-negative bacteria?

Accepted Answer

Gram-negative bacteria have an outer membrane that restricts the entry of hydrophobic compounds found in essential oils.

Question 20

A scientist is using a HEPA filter to sterilize air in a laboratory. What is the minimum particle size that a standard HEPA filter can remove from the air?

Accepted Answer

$$0.3\ \mu\mathrm{m}$$

Chapter 7 – The Control of Microbial Growth: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards