Question 1

Which biosafety level (BSL) is appropriate for handling microbes that cause serious or potentially lethal diseases through respiratory transmission, and what is a key feature of this level?

Accepted Answer

BSL-3; requires specialized ventilation systems and controlled access

Question 2

Which method would be most effective for sterilizing heat-sensitive medical equipment, and why?

Accepted Answer

Ethylene oxide gas, because it penetrates plastic and fabric without heat

Question 3

A hospital needs to sterilize surgical instruments that may be contaminated with prions. Which method should be used?

Accepted Answer

Incineration, because it destroys all forms of microbial life including prions

Question 4

Which term describes the process of reducing microbial load on living tissue through gentle scrubbing and mild chemicals, such as handwashing?

Accepted Answer

Degerming

Question 5

A chemical agent that inhibits the growth and reproduction of fungi without killing them is best described as:

Accepted Answer

Fungistatic

Question 6

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

Accepted Answer

A constant percentage of microbes die during each time interval

Question 7

A laboratory technician uses a membrane filter to sterilize a liquid sample. Which microbes are most likely to pass through the filter?

Accepted Answer

Some viruses

Question 8

Which physical method of microbial control is most appropriate for preserving laboratory cultures by inhibiting metabolism without killing the microbes?

Accepted Answer

Lyophilization

Question 9

A disinfectant is tested using the disk-diffusion assay. What does a large zone of inhibition indicate?

Accepted Answer

The disinfectant is more effective at stopping bacterial growth

Question 10

Which chemical agent is both an antiseptic and a disinfectant, works by denaturing proteins and disrupting membranes, and is commonly used for skin cleaning before surgery?

Accepted Answer

Alcohols

Question 11

A positive in-use test for a disinfectant solution means:

Accepted Answer

Microbes are growing in the disinfectant, indicating contamination

Question 12

Which of the following is an advantage of using supercritical carbon dioxide for sterilization?

Accepted Answer

It penetrates cells and is suitable for delicate tissues and medical devices

Question 13

Which method is most appropriate for disinfecting air in an operating room?

Accepted Answer

HEPA filtration

Question 14

Which chemical agent is used for surgical hand scrubs, acts as an antiseptic by disturbing cell membranes, and is an example of a bisbiguanide?

Accepted Answer

Chlorhexidine

Question 15

A food manufacturer wants to create shelf-stable milk that does not require refrigeration. Which method should be used?

Accepted Answer

Ultra-high temperature (UHT) treatment

Question 16

Which of the following is a high-level germicide, capable of killing endospores with sufficient contact time?

Accepted Answer

Ethylene oxide

Question 17

A scientist is studying the effectiveness of a new disinfectant. She calculates the D-value, which is defined as:

Accepted Answer

The time required to reduce the microbial population by 90%

Question 18

Which physical method of microbial control is most likely to cause double-strand breaks in DNA, leading to sterilization of heat-sensitive medical items?

Accepted Answer

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

Question 19

A cleaning crew uses bleach to clean a public restroom. Which term best describes this process?

Accepted Answer

Disinfection

Question 20

Which equation best represents the microbial death rate during sterilization, where $$N_t is $$the number of microbes at time $$t$$, $$N_0 is $$the initial number, and $$k is $$the death rate constant?

Accepted Answer

$$N_t = N_0$ 	imes e$$^{-kt}$$

Control of Microbial Growth: Methods, Agents, and Laboratory Safety

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