Question 1

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

Accepted Answer

Sterilization removes all forms of microbial life, including endospores, while disinfection eliminates most pathogens but not necessarily all microbes or endospores.

Question 2

A hospital is preparing surgical instruments for use. Which method would ensure complete sterilization, and what are the standard conditions for this process?

Accepted Answer

Autoclaving at $$121^\circ C$$ for 15 minutes under pressure

Question 3

Which of the following statements about antiseptics and disinfectants is correct?

Accepted Answer

Antiseptics are safe for use on living tissue, while disinfectants are intended for use on inanimate surfaces.

Question 4

Which of the following is a correct description of the effect of cold temperatures (such as $$4^\circ C$$ refrigeration) on microbial growth?

Accepted Answer

Cold temperatures are microbistatic, slowing or stopping growth but not killing microbes.

Question 5

A food processing plant wants to reduce microbial load in milk without significantly altering its taste. Which pasteurization method is most appropriate, and what are its standard conditions?

Accepted Answer

Continuous (high-temperature, short-time) pasteurization at $$72^\circ C$$ for 15 seconds

Question 6

Which of the following chemical agents is correctly matched with its primary use?

Accepted Answer

Chlorhexidine: surgical scrub and preoperative skin preparation

Question 7

Why was hexachlorophene discontinued for use in newborn nurseries?

Accepted Answer

It was found to cause neurotoxicity in infants.

Question 8

Silver nitrate was historically used in newborns' eyes to prevent which infection, and what is commonly used today for the same purpose?

Accepted Answer

Gonococcal ophthalmia; erythromycin ointment is now commonly used.

Question 9

Which of the following best explains how halogens such as chlorine and iodine act as antimicrobial agents?

Accepted Answer

They are strong oxidizers that disrupt proteins and nucleic acids.

Question 10

A virus is described as having a helical capsid, no envelope, and a single-stranded RNA genome. Which of the following best describes its structure?

Accepted Answer

A naked, helical virus with ssRNA

Question 11

Which step in the viral replication cycle is responsible for the removal of the protein coat from the viral genome?

Accepted Answer

Uncoating during penetration

Question 12

A researcher is using a plaque assay to quantify bacteriophage. What does each plaque represent?

Accepted Answer

A zone of cell lysis caused by a single infectious phage particle

Question 13

Which of the following best describes the host range of a virus?

Accepted Answer

It is usually limited to closely related species due to specific attachment interactions.

Question 14

Which of the following is a distinguishing feature of prions compared to viruses?

Accepted Answer

Prions are infectious proteins without nucleic acids, while viruses contain nucleic acids.

Question 15

A patient is diagnosed with a persistent viral infection. Which of the following best describes this type of infection?

Accepted Answer

The virus remains in the host for long periods, often with ongoing low-level replication.

Question 16

Which of the following best explains why ethylene oxide is used for sterilizing heat-sensitive medical equipment?

Accepted Answer

It is a gaseous sterilant that can penetrate materials and kill all forms of microbes, including spores, without heat.

Question 17

Which of the following is a correct sequence of steps in the replication cycle of an animal virus?

Accepted Answer

Attachment, penetration and uncoating, biosynthesis, assembly, release

Question 18

A virus is found to cause cell death in tissue culture, resulting in visible changes to the cells. What is this phenomenon called?

Accepted Answer

Cytopathic effect (CPE)

Question 19

Which of the following best describes the action of surfactants such as soap in controlling microorganisms?

Accepted Answer

They emulsify oils and remove microbes from surfaces through mechanical action.

Question 20

A retrovirus requires a specific enzyme for its replication cycle. Which enzyme is this, and what is its function?

Accepted Answer

Reverse transcriptase; it synthesizes DNA from an RNA template.

Control of Microbial Growth and Viruses: Study Guide

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