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 grows optimally at $$37^\circ C$$ and can survive between $$20^\circ C$$ and $$45^\circ C. $$Which category does it belong to?

Accepted Answer

Mesophile

Question 5

Which of the following best explains why 100% ethanol is less effective as a disinfectant than 70% ethanol?

Accepted Answer

Water is required for protein denaturation, which is less efficient in pure ethanol.

Question 6

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

Accepted Answer

Halogens oxidize proteins, inactivating enzymes and leading to microbial death.

Question 7

A patient is infected with a Gram-positive bacterium. Which antimicrobial agent would be most effective by interfering with the cross-linking of NAM subunits in the cell wall?

Accepted Answer

Penicillin

Question 8

Which of the following mechanisms is NOT a common way bacteria develop resistance to antibiotics?

Accepted Answer

Increasing the permeability of the cell wall to allow more drug entry

Question 9

Which of the following best describes the principle of selective toxicity?

Accepted Answer

A drug targets the infectious agent without harming the host.

Question 10

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.

Question 11

Which of the following best explains why pickling is an effective method of food preservation?

Accepted Answer

High salt and acid concentrations create a hypertonic environment, causing plasmolysis in most microbes.

Question 12

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

Accepted Answer

Superoxide dismutase

Question 13

A laboratory is testing the effectiveness of a new disinfectant. Which standard is commonly used to compare the effectiveness of disinfectants?

Accepted Answer

Phenol coefficient

Question 14

Which of the following best describes the action of sulfonamides?

Accepted Answer

They competitively inhibit folic acid synthesis, which is necessary for nucleic acid synthesis.

Question 15

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

Accepted Answer

Membrane filtration

Question 16

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

Accepted Answer

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

Question 17

Which of the following antimicrobial agents is most effective against Mycobacterium tuberculosis by disrupting mycolic acid formation?

Accepted Answer

Isoniazid

Question 18

A bacterium is classified as a facultative anaerobe. Which of the following best describes its growth pattern in a test tube of thioglycollate broth?

Accepted Answer

Growth throughout the tube, but denser at the top where oxygen is present.

Question 19

Which of the following statements about UV radiation as a microbial control method is correct?

Accepted Answer

UV radiation causes thymine dimers in DNA, inhibiting replication and transcription.

Chapter 9 & 10

Study Guide - Practice Questions

Study Guide - Flashcards