Question 1

Which physical method of microbial control is most effective for sterilizing heat-sensitive medical equipment, such as plastic syringes, without causing damage to the material?

Accepted Answer

Ionizing radiation (gamma rays)

Question 2

A hospital is preparing to sterilize surgical instruments using an autoclave. What are the standard conditions required to achieve sterilization in an autoclave?

Accepted Answer

121°C, 15 psi, 15 minutes

Question 3

Which of the following statements best explains why nonenveloped viruses are generally more resistant to harsh environmental conditions than enveloped viruses?

Accepted Answer

Nonenveloped viruses lack a lipid membrane, making them less susceptible to agents that disrupt membranes.

Question 4

A microbiologist is using a membrane filter with a pore size of 0.22 μm to sterilize a solution. Which type of microorganism will NOT be trapped by this filter?

Accepted Answer

Smallest viruses

Question 5

Which chemical method of microbial control is most appropriate for disinfecting drinking water, and what is its primary mechanism of action?

Accepted Answer

Halogens (chlorine); damage enzymes by denaturation

Question 6

A food processing plant wants to extend the shelf life of strawberries without using heat. Which physical method should they use, and what is the effect on microbial DNA?

Accepted Answer

Ionizing radiation; causes breaks in microbial DNA

Question 7

Which biosafety level (BSL) is required for handling pathogens such as Ebola virus, and what is a key feature of this level?

Accepted Answer

BSL-4; use of full-body, positive pressure suits and isolated facilities

Question 8

Which term describes the reduction of microbial numbers on living tissue, such as skin, before surgery?

Accepted Answer

Antisepsis

Question 9

A scientist is evaluating the effectiveness of a new disinfectant using the use-dilution test. What result indicates the disinfectant is most effective?

Accepted Answer

No growth occurs at the highest dilution

Question 10

Which of the following is the ultimate means of sterilization for materials that cannot be treated with moist heat?

Accepted Answer

Incineration

Question 11

Why is hydrogen peroxide not useful for treating open wounds, despite its effectiveness as a surface disinfectant?

Accepted Answer

It is rapidly broken down by catalase in human tissues.

Question 12

Which of the following best describes the decimal reduction time (D value) in microbial control?

Accepted Answer

The time required to reduce the microbial population by 90%

Question 13

Which method is most suitable for long-term preservation of microbial cultures, and why?

Accepted Answer

Lyophilization; prevents formation of damaging ice crystals

Question 14

A patient is prescribed a topical ointment containing 1% silver nitrate to prevent blindness caused by Neisseria gonorrhoeae. Which category of chemical control does this represent?

Accepted Answer

Heavy metals

Question 15

Which physical method of microbial control is most effective for removing bacteria from air in hospital operating rooms?

Accepted Answer

HEPA filtration

Question 16

Which of the following is a disadvantage of using gaseous agents for sterilization in hospitals?

Accepted Answer

They are often highly explosive and potentially carcinogenic.

Question 17

Which term describes the destruction of all microorganisms and viruses on or in an object?

Accepted Answer

Sterilization

Question 18

Why are fungi generally more resistant to osmotic pressure than bacteria?

Accepted Answer

Fungi have cell walls that allow them to tolerate hypertonic environments.

Question 19

Which chemical method is most effective for sterilizing medical equipment contaminated with bacterial endospores?

Accepted Answer

Peracetic acid (oxidizing agent)

Question 20

A laboratory technician is preparing a batch of yogurt. Which method is used to control microbial growth in milk for yogurt production, and what is its effect?

Accepted Answer

Pasteurization; reduces spoilage organisms and pathogens without sterilizing

Controlling Microbial Growth in the Environment

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