Question 1

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

Accepted Answer

Sterilization removes all living microbes, while disinfection only kills pathogenic microbes.

Question 2

A hospital uses an autoclave to sterilize surgical instruments. What are the standard parameters for effective autoclaving?

Accepted Answer

$$15$$ $$lbs/in^2$$ pressure, $$121.5^\circ C$$ temperature, $$15$$ minutes$$

Question 3

Which of the following is a limitation of using an autoclave for sterilization?

Accepted Answer

Oily substances are not effectively sterilized in an autoclave.

Question 4

A bacterium that grows optimally at $$37^\circ C$$ but can survive between $$20^\circ C$$ and $$45^\circ C is $$classified as a:

Accepted Answer

Mesophile

Question 5

Which of the following best explains why pickling (using salt and vinegar) is an effective method of food preservation?

Accepted Answer

High salt and acid concentrations create hypertonic and acidic environments that inhibit most microbial growth.

Question 6

Which enzyme is responsible for converting superoxide ($$O_2$$^-$$) into hydrogen peroxide (H_2O_2$) and oxygen (O_2$) in bacteria?

Accepted Answer

Superoxide dismutase (SOD)

Question 7

A facultative anaerobe is best described as an organism that:

Accepted Answer

Can grow in the presence or absence of oxygen.

Question 8

Which of the following statements about halophiles is correct?

Accepted Answer

Halophiles grow optimally at high salt concentrations by maintaining a high internal solute concentration.

Question 9

Which physical method of microbial control is most appropriate for sterilizing heat-sensitive liquids such as certain pharmaceuticals or blood solutions?

Accepted Answer

Membrane filtration

Question 10

Which of the following best describes the mechanism by which ultraviolet (UV) light damages microbial DNA?

Accepted Answer

It causes adjacent thymine bases to dimerize, disrupting DNA replication.

Question 11

Which of the following chemical agents is most effective for disinfecting air in hospital wards and pharmaceutical filling rooms?

Accepted Answer

High-efficiency particulate air (HEPA) filtration

Question 12

Which of the following is a property of an ideal chemical agent for microbial control?

Accepted Answer

It is fast-acting, inexpensive, stable during storage, and harmless to humans and objects.

Question 13

Which of the following statements about the use of alcohols as antiseptics is correct?

Accepted Answer

Alcohols denature proteins and disrupt membranes, but are not sporocidal.

Question 14

Which of the following best explains why hydrogen peroxide is not recommended for use on open wounds?

Accepted Answer

Catalase in human tissues converts hydrogen peroxide to water and oxygen, reducing its effectiveness.

Question 15

Which of the following is the primary mechanism by which penicillins inhibit bacterial growth?

Accepted Answer

They inhibit cell wall synthesis by preventing cross-linkage of NAM subunits.

Question 16

Sulfonamides are effective antimicrobial agents because they:

Accepted Answer

Interfere with folic acid synthesis, which is necessary for nucleic acid synthesis in bacteria.

Question 17

Which of the following is a mechanism by which bacteria can acquire resistance to antibiotics?

Accepted Answer

Acquisition of R plasmids via transformation, transduction, or conjugation.

Question 18

Which of the following best describes the principle of selective toxicity in antimicrobial therapy?

Accepted Answer

The drug kills or inhibits the infectious agent without harming the host.

Question 19

Which of the following is a reason why antibiotics are not effective against the common cold?

Accepted Answer

Antibiotics target bacteria, while the common cold is caused by viruses.

Microbial Control: Physical and Chemical Methods, and Factors Affecting Microbial Growth

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