Question 1

Which of the following microbial forms is the most resistant to physical and chemical methods of control?

Accepted Answer

Prions

Question 2

A hospital wants to sterilize heat-sensitive plastic syringes. Which method is most appropriate?

Accepted Answer

Ethylene oxide gas sterilization

Question 3

Which of the following best describes the action of surfactants such as soaps and detergents?

Accepted Answer

They disrupt cell membranes, aiding in the removal of microbes

Question 4

Why are non-enveloped viruses generally more resistant to disinfectants than enveloped viruses?

Accepted Answer

They lack a lipid envelope that is easily targeted by chemicals

Question 5

A microbiologist is preparing a solution for intravenous injection and needs to remove all bacteria, including the smallest. Which filter pore size should be used?

Accepted Answer

$$0.22\ \mu m$$

Question 6

Which of the following statements about autoclaving is correct?

Accepted Answer

It sterilizes by using steam under pressure at $$121^{\circ}C$ and 15 psi for 15 minutes

Question 7

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

Accepted Answer

It is inactivated by catalase enzyme present in tissues

Question 8

A food manufacturer wants to preserve fruit juice without altering its taste or nutritional value. Which method is most appropriate?

Accepted Answer

Pasteurization at $$72^{\circ}C$ for 15 seconds

Question 9

Which of the following best explains why Gram-negative bacteria are generally more resistant to chemical disinfectants than Gram-positive bacteria?

Accepted Answer

They possess an outer membrane containing lipopolysaccharide (LPS)

Question 10

Which of the following is the primary mechanism by which UV radiation kills microorganisms?

Accepted Answer

Formation of thymine dimers in DNA

Question 11

A patient with a deep puncture wound is at risk for infection by anaerobic bacteria. Which chemical agent would be most effective for disinfecting the wound?

Accepted Answer

Hydrogen peroxide

Question 12

Which of the following terms refers to the reduction of microbial population to levels considered safe by public health standards?

Accepted Answer

Sanitization

Question 13

Which of the following is a correct statement about the use of heavy metals in microbial control?

Accepted Answer

They denature proteins by binding to sulfur atoms in cysteine

Question 14

Which of the following is a disadvantage of using ethylene oxide gas for sterilization?

Accepted Answer

It is highly explosive and potentially carcinogenic

Question 15

Which of the following best describes the effect of placing a bacterial cell in a hypertonic solution?

Accepted Answer

The cell will lose water and shrink (plasmolysis)

Question 16

Which of the following is true regarding the use of filtration for sterilization?

Accepted Answer

It can sterilize heat-sensitive liquids by removing microbes based on size

Question 17

Which of the following statements about pasteurization is correct?

Accepted Answer

It reduces the number of pathogens and spoilage organisms without sterilizing

Question 18

Which of the following chemical agents is most likely to be used to sterilize medical equipment that cannot withstand heat or moisture?

Accepted Answer

Ethylene oxide

Question 19

Which of the following is a correct match between the agent and its primary cellular target?

Accepted Answer

Phenolics – Cell membranes and proteins

Question 20

A laboratory technician is preparing a bacterial culture for long-term storage. Which method is most appropriate to preserve viability for years?

Accepted Answer

Lyophilization (freeze-drying)

Controlling Microbial Growth in the Environment: Methods and Principles

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