Q: If a population of 10,000 bacteria is exposed to a treatment that kills 90% of the population every minute, how many bacteria remain after 2 minutes? Use the formula $$N_t = N_0$ \times (0.1)^t$$, where $$N_0 is $$the initial number and $$t is $$time in minutes.

$$N_2 = 10$$,000 \times $$(0.1)^2 = 100$

Question 1

Which of the following best describes the process of commercial sterilization in the food industry?

Accepted Answer

Killing Clostridium botulinum endospores to prevent foodborne illness

Question 2

A hospital uses an autoclave to sterilize surgical instruments. What is the primary mechanism by which the autoclave achieves sterilization?

Accepted Answer

Denaturation of proteins by moist heat under pressure

Question 3

Which term refers specifically to the removal of pathogens from living tissue?

Accepted Answer

Antisepsis

Question 4

A food processing plant uses pasteurization at $$72^{\circ}C$ for 15 seconds. What is the main reason some thermoresistant organisms are not a concern after this treatment?

Accepted Answer

They cannot replicate at refrigeration temperatures

Question 5

Which of the following chemical agents is most effective against acid-fast bacteria such as Mycobacterium?

Accepted Answer

Phenol and phenolics

Question 6

A researcher is testing the effectiveness of a new disinfectant using the disc-diffusion method. Which factor would NOT affect the outcome of this test?

Accepted Answer

Color of the agar plate

Question 7

Which physical method of microbial control works primarily by causing plasmolysis in microbial cells?

Accepted Answer

Osmotic pressure

Question 8

If a population of 10,000 bacteria is exposed to a treatment that kills 90% of the population every minute, how many bacteria remain after 2 minutes? Use the formula $$N_t = N_0$ 	imes (0.1)^t$$, where $$N_0 is $$the initial number and $$t is $$time in minutes.

Accepted Answer

$$N_2 = 10$$,000 	imes $$(0.1)^2 = 100$

Question 9

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

Accepted Answer

Alcohols require water to effectively denature proteins

Question 10

A patient is treated with a mouthwash containing chlorohexidine. Which class of chemical agent does this belong to, and what is its primary mode of action?

Accepted Answer

Biguanides; disrupt plasma membranes

Question 11

Which of the following is a reason why biofilms can reduce the effectiveness of chemical disinfectants?

Accepted Answer

Biofilms slow the diffusion of chemicals into the bacterial community

Question 12

Which physical method of microbial control is LEAST likely to achieve sterilization?

Accepted Answer

Pasteurization

Question 13

A laboratory technician uses a HEPA filter in a biosafety cabinet. What is the primary purpose of this filter?

Accepted Answer

To remove most microbes, including bacteria and fungal spores, from the air

Question 14

Which chemical food preservative is used to prevent endospore germination in processed meats?

Accepted Answer

Nitrite

Question 15

A nurse is cleaning a wound using a solution that removes microbes from a limited area. Which term best describes this process?

Accepted Answer

Degerming

Question 16

Which of the following is NOT a typical action of microbial control agents?

Accepted Answer

Increase in microbial replication rate

Question 17

A restaurant uses acid-anionic detergents to clean utensils. What is the main microbial control function of these detergents?

Accepted Answer

Sanitization by disrupting the plasma membrane

Question 18

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

Accepted Answer

Microbes die at a constant rate, resulting in a logarithmic decrease in survivors

Question 19

Which of the following is a plausible reason for the widespread resistance to Triclosan among bacteria?

Accepted Answer

Triclosan is a bisphenol used extensively in consumer products

The Control of Microbial Growth: Principles, Methods, and Applications

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