Q: Which equation best represents the relationship between the number of surviving microbes ($$N) $$after exposure to a sterilization protocol for time $$t$$, given an initial population $$N_0$$ and decimal reduction time $$D$$?

$$N = N_0$ \times 10$$^{-t/D}$$

Question 1

Which of the following best describes the difference between disinfectants, antiseptics, and sterilants?

Accepted Answer

Disinfectants are used on inanimate surfaces to kill most microbes, antiseptics are safe for use on living tissue, and sterilants kill all microbes including endospores and viruses.

Question 2

A hospital is deciding how to clean surgical instruments that will penetrate sterile tissues. Which protocol is most appropriate?

Accepted Answer

Sterilization

Question 3

Which of the following factors is NOT used to determine the biological safety level (BSL) required for handling a specific pathogen?

Accepted Answer

Color of the pathogen

Question 4

A laboratory technician is working with Mycobacterium tuberculosis. Which BSL precautions are required?

Accepted Answer

BSL-3: Restricted access, medical surveillance, respirator, biological safety cabinet, directional airflow

Question 5

Which of the following best explains why commercial sterilization of canned foods is not true sterilization?

Accepted Answer

It targets pathogens responsible for spoilage and foodborne diseases but allows nonpathogenic organisms to survive.

Question 6

A patient develops a nosocomial infection after surgery. Which of the following is a plausible way bacteria could have been introduced?

Accepted Answer

Through contaminated surgical instruments that were not properly sterilized

Question 7

Which suffix is used to indicate a chemical or physical method that kills microorganisms, and what does the prefix specify?

Accepted Answer

Suffix '-cide' indicates killing; prefix specifies the type of microbe killed.

Question 8

A microbial death curve is plotted as a semilog plot. If the decimal reduction time (D-value) for a protocol is 2 minutes, how long will it take to reduce a population from $$10^6 to$$ $$10^2$$ cells?

Accepted Answer

$$12 	ext{ minutes}$$

Question 9

Which of the following is a reason to choose a bacteriostatic treatment over a bactericidal one?

Accepted Answer

Bacteriostatic treatments preserve the integrity of the item and are less toxic.

Question 10

Which physical method of microbial control is most effective for sterilizing heat-sensitive medical equipment such as catheters packaged in plastic?

Accepted Answer

Ethylene oxide gas sterilization

Question 11

Why is boiling not considered a reliable sterilization method in clinical settings?

Accepted Answer

Boiling does not kill endospores, which can survive for hours.

Question 12

Which equation best represents the relationship between the number of surviving microbes ($$N) $$after exposure to a sterilization protocol for time $$t$$, given an initial population $$N_0$$ and decimal reduction time $$D$$?

Accepted Answer

$$N = N_0$ 	imes 10$$^{-t/D}$$

Question 13

Which of the following statements about HEPA filters is correct?

Accepted Answer

HEPA filters remove bacteria, endospores, and many viruses from air, nearly sterilizing it.

Question 14

Which chemical disinfectant works by denaturing proteins and disrupting membranes, and is commonly used in hand sanitizers and for degerming skin before injection?

Accepted Answer

Isopropyl alcohol

Question 15

Which of the following is a drawback of using nitrites as food preservatives?

Accepted Answer

Nitrites can form carcinogenic nitrosamines when exposed to heat.

Question 16

A disk-diffusion assay is performed to compare two disinfectants against Staphylococcus aureus. Disinfectant A produces a zone of inhibition of 20 mm, while Disinfectant B produces a zone of 10 mm. Assuming both are equally soluble, which is more effective?

Accepted Answer

Disinfectant A, because larger zones indicate greater inhibition.

Question 17

Which of the following best explains why soaps are not considered disinfectants?

Accepted Answer

Soaps mechanically remove microbes but do not kill or inhibit their growth.

Question 18

Which chemical agent is most effective for sterilizing heat-sensitive items and is highly explosive, requiring careful handling?

Accepted Answer

Ethylene oxide

Question 19

Which of the following is a major advantage of using supercritical carbon dioxide ($$	ext{scCO}_2) $$for sterilization?

Accepted Answer

It preserves the integrity of the object and is effective at low temperatures.

Question 20

Which method is used to test whether a disinfectant solution actively used in a clinical setting is contaminated with microbes?

Accepted Answer

In-use test

Control of Microbial Growth: Physical and Chemical Methods, Safety Levels, and Testing

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