Question 1

Which of the following best describes the process of sterilization?

Accepted Answer

The destruction or removal of all forms of microbial life, including endospores.

Question 2

A hospital uses an autoclave set at 121°C and 15 psi for 15 minutes to sterilize surgical instruments. What is the primary mechanism by which the autoclave kills microbes?

Accepted Answer

Protein denaturation by moist heat.

Question 3

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

Accepted Answer

Microbial populations die at a constant rate, which appears as a straight line when plotted logarithmically.

Question 4

Why are Gram-negative bacteria generally more resistant to chemical biocides than Gram-positive bacteria?

Accepted Answer

They possess an outer membrane that restricts entry of chemicals.

Question 5

Which of the following methods is most appropriate for sterilizing heat-sensitive plastic labware?

Accepted Answer

Ionizing radiation (e.g., gamma rays).

Question 6

A solution contains $$1 	imes 10^6$ bacteria. If the death rate is 90% per minute, how many bacteria remain after 2 minutes?

Accepted Answer

$$1 	imes 10^4$

Question 7

Which of the following statements about pasteurization is TRUE?

Accepted Answer

High-temperature short-time (HTST) pasteurization is typically performed at 72°C for 15 seconds.

Question 8

Which chemical disinfectant is most effective against a broad spectrum of microbes but is NOT sporicidal and is commonly used in pools and drinking water?

Accepted Answer

Chlorine

Question 9

Why are naked viruses generally more resistant to chemical disinfectants than enveloped viruses?

Accepted Answer

Their protein capsid is more resistant to drying, acid, and detergents.

Question 10

Which of the following is a major advantage of glutaraldehyde over other chemical disinfectants?

Accepted Answer

It can sterilize delicate surgical instruments without heat.

Question 11

A surface is contaminated with vomit (containing organic matter) and another with a sneeze (mostly respiratory droplets). Why might your choice of disinfectant differ for these two surfaces?

Accepted Answer

Organic matter can inactivate some disinfectants, requiring a different or stronger agent for vomit.

Question 12

Which of the following statements about alcohols as disinfectants is correct?

Accepted Answer

Alcohols denature proteins and dissolve lipids.

Question 13

Which of the following is the best explanation for why handwashing is considered the single most effective measure for microbial growth control?

Accepted Answer

It mechanically removes microbes, breaking the chain of transmission.

Question 14

Which of the following is a limitation of using the autoclave for sterilization?

Accepted Answer

It cannot sterilize materials that are damaged by moisture or heat.

Question 15

Which of the following best describes the action of ionizing radiation on microbial cells?

Accepted Answer

It produces free radicals that damage cellular components.

Question 16

Which of the following is the main reason why prions are the most resistant to microbial control methods?

Accepted Answer

They lack nucleic acids and are not affected by most sterilization methods.

Question 17

Which of the following is the correct order of microbial resistance to chemical biocides, from most resistant to least resistant?

Accepted Answer

Prions \u003e Endospores \u003e Mycobacteria \u003e Gram-negative bacteria \u003e Viruses with lipid envelopes

Question 18

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

Accepted Answer

They are strongly bactericidal against Gram-positive bacteria.

Question 19

A food processing plant wants to prevent the germination of endospores in cured meats. Which chemical is most likely to be used for this purpose?

Accepted Answer

Sodium nitrate or nitrite

Question 20

Which of the following best explains why hydrogen peroxide is especially effective against anaerobic bacteria?

Accepted Answer

Anaerobic bacteria lack catalase to neutralize toxic oxygen products.

The Control of Microbial Growth: Principles and Methods

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