Q: A hospital uses an autoclave to sterilize surgical instruments. What is the standard pressure and temperature combination used to achieve sterilization in an autoclave?

$$15\ \text{psi}$$ and $$121\ ^\circ\text{C}$$ for $$15\ \text{minutes}$$

Question 1

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization destroys all microbial life, including endospores, while disinfection destroys most microbial life but not endospores.

Question 2

Arrange the following microbial forms in order from most resistant to least resistant to control measures: prions, bacterial endospores, enveloped viruses, gram-positive bacteria.

Accepted Answer

Prions \u003e Bacterial endospores \u003e Gram-positive bacteria \u003e Enveloped viruses

Question 3

A hospital uses an autoclave to sterilize surgical instruments. What is the standard pressure and temperature combination used to achieve sterilization in an autoclave?

Accepted Answer

$$15\ 	ext{psi}$$ and $$121\ ^\circ	ext{C}$$ for $$15\ 	ext{minutes}$$

Question 4

Which of the following is the primary mode of action for surfactants such as quaternary ammonium compounds?

Accepted Answer

Disruption of the cell membrane

Question 5

A daycare teacher needs to disinfect toys after a Rotavirus outbreak. Which level of microbial control is most appropriate and why?

Accepted Answer

Disinfection, because it destroys most pathogens including viruses but does not require sterilization.

Question 6

Which of the following statements about moist heat and dry heat is correct?

Accepted Answer

Moist heat requires lower temperatures and shorter exposure times than dry heat to achieve sterilization.

Question 7

Which chemical agent is most extensively used for disinfection of drinking water and what is its primary mode of action?

Accepted Answer

Sodium hypochlorite (bleach); denaturation of proteins

Question 8

A laboratory technician is preparing Urea broth, which cannot withstand high temperatures. Which method is most appropriate for sterilizing the broth?

Accepted Answer

Filtration

Question 9

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

Accepted Answer

Water is required for protein coagulation, enhancing microbicidal activity.

Question 10

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

Accepted Answer

They are ineffective against endospores and some pathogens such as Pseudomonas.

Question 11

Which physical method of microbial control is most appropriate for sterilizing heat-sensitive medical devices such as plastic syringes?

Accepted Answer

Ionizing radiation (gamma rays or X-rays)

Question 12

What is the primary cellular target of aldehyde-based disinfectants such as glutaraldehyde?

Accepted Answer

Proteins (denaturation)

Question 13

A child scrapes her knee on the playground. Which method and level of microbial control is most appropriate for cleaning the wound?

Accepted Answer

Antisepsis using an alcohol-based antiseptic

Question 14

Which of the following statements about UV radiation is correct?

Accepted Answer

It causes the formation of pyrimidine dimers in DNA, inhibiting replication and transcription.

Question 15

Which of the following is NOT a desirable quality of an antimicrobial chemical?

Accepted Answer

High toxicity to human tissues

Question 16

Which of the following best describes the effect of adding large amounts of salt or sugar to food as a method of microbial control?

Accepted Answer

It creates a hypertonic environment, causing plasmolysis in bacteria.

Question 17

Which of the following is the correct definition of thermal death time (TDT)?

Accepted Answer

The shortest length of time required to kill all test microbes at a specified temperature.

Question 18

Which of the following is a major limitation of using hydrogen peroxide as a sterilant?

Accepted Answer

It is sporicidal only in high concentrations.

Question 19

Which of the following is a real-world application of using phenolic compounds in microbial control?

Accepted Answer

Disinfecting animal quarters and drains

Question 20

Which of the following factors does NOT affect the rate at which microbes are killed by antimicrobial agents?

Accepted Answer

The color of the microbial cells

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