Question 1

Which physical method of microbial control is most effective for sterilizing heat-sensitive liquids, such as culture media, without damaging their components?

Accepted Answer

Filtration

Question 2

A hospital needs to sterilize mattresses and electronic equipment. Which method is most appropriate and why?

Accepted Answer

Gaseous agents, because they can penetrate crevices and do not damage sensitive materials

Question 3

Why is moist heat generally more effective than dry heat for microbial control?

Accepted Answer

Water is a better conductor of heat than air, allowing for more efficient transfer of energy

Question 4

Which equation best represents the decomposition of hydrogen peroxide by catalase, as used in oxidizing agent disinfection?

Accepted Answer

$$2H_2O_2 \rightarrow 2H_2O + O_2$

Question 5

A food manufacturer wants to preserve fruit by inhibiting microbial growth. Which method is most effective and why?

Accepted Answer

Desiccation, because removing water inhibits most microbial growth

Question 6

Which of the following statements about autoclaving is correct?

Accepted Answer

Autoclaving uses steam under pressure to reach temperatures above boiling, effectively killing endospores

Question 7

Which chemical method is most appropriate for disinfecting surfaces contaminated with prions?

Accepted Answer

Enzymes such as prionzyme

Question 8

A laboratory technician needs to ensure that a batch of media is sterile. Which indicator would best confirm successful autoclaving?

Accepted Answer

Biological indicator containing endospores that fail to grow after incubation

Question 9

Which of the following is a limitation of using hydrogen peroxide as a disinfectant for open wounds?

Accepted Answer

It is neutralized by catalase in human cells, reducing its effectiveness

Question 10

Which biosafety level (BSL) is required for handling microbes that cause severe or fatal disease?

Accepted Answer

BSL-4

Question 11

Why is boiling not recommended for true sterilization in medical settings?

Accepted Answer

Boiling does not destroy bacterial endospores and some viruses

Question 12

Which physical method is most suitable for long-term preservation of microbial cultures?

Accepted Answer

Lyophilization (freeze-drying)

Question 13

Which chemical agent is commonly used in vaccines to prevent microbial growth and is safe in small amounts?

Accepted Answer

Thimerosal (Hg2+)

Question 14

What is the main mechanism by which halogens such as chlorine and iodine act as antimicrobial agents?

Accepted Answer

Oxidizing and denaturing microbial enzymes

Question 15

Which of the following statements about refrigeration and freezing is correct?

Accepted Answer

Slow freezing is more effective than quick freezing at inhibiting microbial growth

Question 16

Which type of radiation is most effective for sterilizing medical equipment that cannot be exposed to heat?

Accepted Answer

Ionizing radiation (gamma rays)

Question 17

Which of the following best explains why fungi are more likely than bacteria to survive in foods preserved by high concentrations of salt or sugar?

Accepted Answer

Fungi are better adapted to survive hypertonic environments

Question 18

Which chemical method is most effective for disinfecting organic matter in healthcare settings, but has a disagreeable odor and possible side effects?

Accepted Answer

Phenols

Question 19

Which of the following is a correct statement about surfactants?

Accepted Answer

Surfactants reduce surface tension of water, aiding in removal of microbes

Question 20

A researcher is working with a highly contagious airborne pathogen. Which physical method should be used to maintain a microbe-free airflow in the laboratory?

Accepted Answer

HEPA filtration

Physical and Chemical Methods of Microbial Control

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