Q: A 5% w/v concentration of a bactericide with a dilution coefficient $$n=3$$ takes 25 minutes to effect killing. What will be the time of kill when it is diluted 8 times?

$$25 \times 8^3$ = 25 \times 512 = 12,800$$ minutes

Question 1

Which of the following best describes the difference between antisepsis and disinfection?

Accepted Answer

Antisepsis is the destruction or inhibition of microorganisms on living tissues, while disinfection is the removal of microorganisms from inanimate objects.

Question 2

A disinfectant has an extinction time of 30 minutes at 25°C and 10 minutes at 35°C. What is the temperature coefficient $$	heta$$ for this disinfectant?

Accepted Answer

$$	heta = \frac{30}{10} = 3$$

Question 3

Which of the following is NOT a property of an ideal disinfectant?

Accepted Answer

Breaks down slowly into toxic byproducts

Question 4

Which group of disinfectants is most likely to be inactivated by organic matter such as blood or pus?

Accepted Answer

Halogens

Question 5

A 5% w/v concentration of a bactericide with a dilution coefficient $$n=3$$ takes 25 minutes to effect killing. What will be the time of kill when it is diluted 8 times?

Accepted Answer

$$25 	imes 8^3$ = 25 	imes 512 = 12,800$$ minutes

Question 6

Which of the following statements about resistance to biocides is correct?

Accepted Answer

Acquired resistance can result from chromosomal mutations or acquisition of plasmids.

Question 7

Which of the following is the correct order of microbial resistance to chemical disinfectants, from most resistant to least resistant?

Accepted Answer

Prions \u003e Endospores \u003e Mycobacteria \u003e Gram-negative bacteria \u003e Viruses with lipid envelopes

Question 8

Which of the following mechanisms is NOT a common mode of action for chemical disinfectants?

Accepted Answer

ATP synthesis enhancement

Question 9

Why is it important to use a neutralizer or dilution immediately after sampling in suspension tests for disinfectant evaluation?

Accepted Answer

To immediately stop the action of the disinfectant and obtain accurate results

Question 10

Which preservative is most effective at pH 4 and below, and is relatively inactive at pH 5 and above?

Accepted Answer

Benzoic acid

Question 11

A hospital needs to disinfect bed linens. According to Spaulding’s classification, what level of disinfection is required?

Accepted Answer

Low-level disinfection

Question 12

Which of the following combinations is used to enhance the antimicrobial activity of disinfectants?

Accepted Answer

Ethanol + Chlorhexidine + Iodine

Question 13

Which of the following factors does NOT affect the efficacy of a chemical disinfectant?

Accepted Answer

Colour of the disinfectant

Question 14

Which of the following statements about preservatives in pharmaceuticals is TRUE?

Accepted Answer

Preservatives must not be toxic in relation to their intended route of administration.

Question 15

Which of the following is a limitation of the membrane filtration method for evaluating disinfectants?

Accepted Answer

Clumping of organisms can lead to inaccurate colony counts.

Question 16

Which of the following is a reason why no single preservative is ideal for all pharmaceutical preparations?

Accepted Answer

Preservatives may be incompatible with other ingredients or containers.

Question 17

Which of the following disinfectants is most likely to be used as a vapor for air disinfection in hospital burn units?

Accepted Answer

Dilute bleach

Question 18

Which of the following is a correct statement about the effect of pH on disinfectant activity?

Accepted Answer

Phenols and benzoic acid are more active in their non-ionized state at acidic pH.

Question 19

Which of the following is a practical implication of a disinfectant with a high concentration exponent $$n$$?

Accepted Answer

Its activity is greatly reduced by dilution.

Chemical Disinfection, Antisepsis, and Preservation: Principles and Applications

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