Q: If a disinfectant kills 90% of microbes every minute, how many minutes will it take to reduce a population from $$10^6 to $$less than 1 microbe?

Approximately 7 minutes, since $$10^6$$ \times $$(0.1)^7 = 1$

Question 1

Which of the following best describes antisepsis?

Accepted Answer

The use of chemical agents to inhibit or destroy microorganisms on living tissue.

Question 2

Semmelweis is known for which major contribution to microbial control?

Accepted Answer

Requiring doctors to wash their hands in lime water before handling patients, reducing maternal mortality.

Question 3

Which term refers to the complete removal or destruction of all microbes from an area?

Accepted Answer

Sterilization

Question 4

A disinfectant kills 50% of microbes every 5 minutes. If you start with 256 microbes, how many will remain after 15 minutes?

Accepted Answer

Question 5

Which of the following is an example of a -static agent?

Accepted Answer

Refrigeration

Question 6

Pasteurization is primarily used to:

Accepted Answer

Reduce food spoilage and kill pathogens using heat.

Question 7

Which of the following is NOT a factor to consider when choosing a microbial control method?

Accepted Answer

Color of the disinfectant

Question 8

Which method is currently the US standard for evaluating disinfectants and antiseptics?

Accepted Answer

Dilution test

Question 9

What is the main difference between disinfection and antisepsis?

Accepted Answer

Disinfection is used on nonliving surfaces, while antisepsis is used on living tissue.

Question 10

Which of the following agents is classified as high-level germicide?

Accepted Answer

Kills all pathogens including endospores

Question 11

Which of the following best describes the action of a bacteriostatic agent?

Accepted Answer

It inhibits bacterial growth without killing them.

Question 12

If a disinfectant kills 90% of microbes every minute, how many minutes will it take to reduce a population from $$10^6 to $$less than 1 microbe?

Accepted Answer

Approximately 7 minutes, since $$10^6$$ 	imes $$(0.1)^7 = 1$

Question 13

Which of the following is a mechanical method of microbial control?

Accepted Answer

Washing hands under running water

Question 14

Which of the following statements about autoclaves is correct?

Accepted Answer

Autoclaves kill all bacteria using high pressure saturated steam at 121°C for 15-20 minutes.

Question 15

Which of the following is most resistant to microbial control methods?

Accepted Answer

Prions

Question 16

What is the main function of the cytoplasmic membrane in microbial cells?

Accepted Answer

Controls passage of chemicals into and out of the cell

Question 17

Which of the following is a correct application of the phenol coefficient?

Accepted Answer

Comparing the efficacy of a disinfectant to phenol; a coefficient greater than 1.0 means the agent is more effective than phenol.

Question 18

Which of the following is an example of an aseptic technique?

Accepted Answer

Flaming lab equipment before use

Question 19

Which of the following is a reason why pasteurization does not achieve sterilization?

Accepted Answer

Pasteurization only kills vegetative bacteria and some viruses, not all microbes.

Question 20

If a disinfectant kills 50% of microbes every 5 minutes, how many 5-minute intervals are required to reduce a population of 256 microbes to less than 1?

Accepted Answer

8 intervals

Microbial Control in the Environment: Principles, Methods, and Evaluation

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