Q: A hospital uses an autoclave to sterilize surgical instruments. What are the standard conditions for autoclaving to achieve sterilization?

$$15\ \text{psi},\ 121^\circ\text{C},\ 15\ \text{min}$$

Q: Which physical method is most appropriate for sterilizing heat-sensitive solutions such as certain vitamins or antibiotics?

Filtration through a $$0.22\ \mu\text{m}$$ membrane

Question 1

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

Accepted Answer

Sterilization removes all forms of microbial life, including endospores, while disinfection destroys only vegetative pathogens.

Question 2

A hospital uses an autoclave to sterilize surgical instruments. What are the standard conditions for autoclaving to achieve sterilization?

Accepted Answer

$$15\ 	ext{psi},\ 121^\circ	ext{C},\ 15\ 	ext{min}$$

Question 3

Which of the following statements about microbial death rate is correct?

Accepted Answer

Microbial populations die at a constant rate when exposed to a lethal agent, which can be plotted as a straight line on a logarithmic scale.

Question 4

Which physical method is most appropriate for sterilizing heat-sensitive solutions such as certain vitamins or antibiotics?

Accepted Answer

Filtration through a $$0.22\ \mu	ext{m}$$ membrane

Question 5

Which of the following is NOT a factor that influences the effectiveness of antimicrobial treatments?

Accepted Answer

The color of the disinfectant

Question 6

A patient receives a wound dressing containing silver sulfadiazine. What is the primary antimicrobial mechanism of silver?

Accepted Answer

Denaturation of proteins

Question 7

Which of the following disinfectants is most effective against endospores?

Accepted Answer

Aldehydes such as glutaraldehyde

Question 8

Why is 70% ethanol more effective as a disinfectant than 100% ethanol?

Accepted Answer

Water is required for protein denaturation and slows evaporation, increasing contact time.

Question 9

Which of the following best explains why bacteria in biofilms are more resistant to disinfectants?

Accepted Answer

The extracellular matrix protects bacteria from exposure to the disinfectant.

Question 10

A laboratory is testing the effectiveness of a new disinfectant using the disk diffusion method. What does a larger zone of inhibition around the disk indicate?

Accepted Answer

Greater effectiveness of the disinfectant against the test organism

Question 11

Which chemical agent is commonly used to sterilize disposable medical supplies and is known to be carcinogenic?

Accepted Answer

Ethylene oxide

Question 12

Which of the following statements about quaternary ammonium compounds (quats) is TRUE?

Accepted Answer

They are more effective against Gram-positive bacteria than Gram-negative bacteria.

Question 13

Which of the following is the best definition of the minimum inhibitory concentration (MIC)?

Accepted Answer

The lowest concentration of a disinfectant or chemotherapeutic agent that prevents visible bacterial growth

Question 14

Which physical method of microbial control is most likely to cause the formation of thymine dimers in DNA?

Accepted Answer

Non-ionizing radiation (UV light)

Question 15

A food processing plant uses peracetic acid to disinfect equipment. What is a major advantage of peracetic acid?

Accepted Answer

It is sporicidal and leaves no toxic residues.

Question 16

Which of the following best describes the effect of high salt or sugar concentrations on microbial cells?

Accepted Answer

They create a hypertonic environment, causing plasmolysis.

Question 17

Which of the following is a limitation of using alcohols as disinfectants?

Accepted Answer

They are not effective against endospores and non-enveloped viruses.

Question 18

A microbiologist is using a broth dilution test to determine the MBC of a new antibiotic. What is the MBC?

Accepted Answer

The lowest concentration of the antibiotic that kills the test organism

Question 19

Which of the following is a reason why moist heat is generally more effective than dry heat for sterilization?

Accepted Answer

Moist heat denatures proteins more efficiently due to better heat transfer.

Question 20

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

Accepted Answer

Chlorine: Disinfection of water supplies

Chapter 7: The Control of Microbial Growth – Study Notes

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