Question 1

Which of the following best describes the process of sterilization?

Accepted Answer

Removing and destroying all microbial life, including endospores

Question 2

A hospital is preparing surgical instruments for use. Which method would be most effective for ensuring all organisms, including endospores, are destroyed?

Accepted Answer

Autoclaving at 121°C and 15 psi for 15 minutes

Question 3

Which of the following best explains why a solution containing $$1 	imes 10^6$ bacteria takes longer to sterilize than a solution containing 5$$ 	imes $$10^5$$ bacteria, assuming all other conditions are equal?

Accepted Answer

A higher number of microbes requires more time for all to be killed, as each decimal reduction time ($$D) $$only reduces the population by 90%

Question 4

A chemical agent that damages the plasma membrane of bacteria is likely to have which of the following effects on human cells?

Accepted Answer

It could also damage human cells, as both have plasma membranes

Question 5

Which of the following statements about decimal reduction time ($$D) is $$correct?

Accepted Answer

$$D is $$the time required to kill 90% of a microbial population at a given temperature

Question 6

A laboratory is testing a new disinfectant using the use-dilution test. Which of the following best describes this method?

Accepted Answer

Metal cylinders are dipped in test bacteria, dried, exposed to disinfectant, and then transferred to culture media to check for survival

Question 7

Which of the following physical methods of microbial control is most appropriate for sterilizing heat-sensitive solutions such as vaccines?

Accepted Answer

Filtration through a membrane filter with pore size $$0.22\ \mu m$$

Question 8

Ionizing radiation, such as X-rays and gamma rays, kills microbes primarily by which mechanism?

Accepted Answer

Creating reactive hydroxyl radicals that damage DNA

Question 9

A food processing plant uses high concentrations of salt to preserve meat. What is the primary mechanism by which this method inhibits microbial growth?

Accepted Answer

Creation of a hypertonic environment causing plasmolysis

Question 10

Which of the following chemical agents is most effective against endospores and is considered a chemical sterilant?

Accepted Answer

Glutaraldehyde

Question 11

A patient is treated with a topical antiseptic before surgery. Which of the following halogen preparations is most likely being used as an antiseptic?

Accepted Answer

Iodine in the form of Betadine (an iodophor)

Question 12

Why are gram-negative bacteria generally more resistant to chemical biocides than gram-positive bacteria?

Accepted Answer

Their outer membrane acts as an additional barrier to many chemicals

Question 13

Which of the following best explains why alcohol is effective against some viruses but not others?

Accepted Answer

Alcohol dissolves lipid envelopes, so it is effective against enveloped viruses but not nonenveloped viruses

Question 14

A dairy company is selecting a surface-active agent for cleaning equipment. Which property makes these agents particularly attractive for this industry?

Accepted Answer

They lower surface tension, aiding in the removal of dirt and microbes

Question 15

A can of pork takes longer to sterilize at a given temperature than a can of soup containing pieces of pork. What is the most likely explanation?

Accepted Answer

Larger solid pieces require more time for heat to penetrate and reach sterilizing temperatures throughout

Question 16

Which of the following statements about aldehydes as disinfectants is correct?

Accepted Answer

Aldehydes inactivate proteins by cross-linking with functional groups such as $$-NH_2$, -OH$, -$$COOH$$, and -SH$

Question 17

Which of the following is a correct match between a chemical agent and its preferred use?

Accepted Answer

Copper sulfate: used as an algicide in water systems

Question 18

A researcher is using the disk-diffusion method to test a new antibiotic. What result would indicate the antibiotic is effective against the test organism?

Accepted Answer

A clear zone of inhibition around the disk

Question 19

Which of the following is a limitation of using alcohols as disinfectants in a clinical setting?

Accepted Answer

They require water to be effective and do not kill nonenveloped viruses

Question 20

A medical device manufacturer needs to sterilize heat-sensitive plastic tubing. Which method is most appropriate?

Accepted Answer

Gaseous sterilization with ethylene oxide

Chapter 7: The Control of Microbial Growth – Study Notes

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