Chapter 13

Question 1

What are fomites?

Answer 1

Inanimate items that may harbor microbes and aid in their transmission.

Question 2

How are the four biological safety levels (BSLs) determined?

Answer 2

• The agent’s infectivity
• Ease of transmission
• Potential disease severity
• The type of work being performed with the agent

Question 3

What is sterilization?

Answer 3

The complete removal or killing of all vegetative cells, endospores, and viruses from the targeted item or environment.

Question 4

What does disinfection do?

Answer 4

Removes potential pathogens from a fomite microbial load is reduced, but microbes may remain unless the chemical used is strong enough to be a sterilant.

Question 5

What does antisepsis mean?

Answer 5

Antisepsis means preventing infection in living tissue.

Question 6

What is antisepsis?

Answer 6

Uses antimicrobial chemicals safe enough for tissues, but microbes may remain unless the chemical used is strong enough to be a sterilant.

Question 7

What is asepsis?

Answer 7

Asepsis is about creating a totally germ-free environment to prevent infections during medical procedures or in a laboratory setting.

Question 8

What does the amount of cleanliness for clinical use depend on?

Answer 8

Whether or not the item will come into contact with sterile tissues (critical item), mucous membranes (semi-critical item), or intact skin (noncritical item).

Question 9

What does it mean if a method ends in -cide or -cidal?

Answer 9

It kills all bacteria immediately.

Question 10

What does it mean if a method ends in -stat or -static?

Answer 10

It inhibits microbial growth.

Question 11

What do microbial death curves demonstrate?

Answer 11

Display the logarithmic decline of living microbes exposed to a method of microbial control.

Question 12

What is the decimal reduction time, or D-value?

Answer 12

The time it takes for a protocol to yield a 1-log (90%) reduction in the microbial population.

Question 13

What should be considered when choosing a microbial control protocol?

Answer 13

• The length of exposure time
• The type of microbe targeted
• Its susceptibility to the protocol
• The intensity of the treatment or concentration of disinfecting agent
• The presence of organics that may interfere with the protocol (body fluids)
• The environmental conditions that may alter the effectiveness of the protocol

Question 14

What does heat have to do with microbes?

Answer 14

Heat is a widely used and highly effective method for controlling microbial growth. Heat can kill microbes by altering their membranes and denaturing proteins.

Question 15

What is the most common laboratory aseptic technique?

Answer 15

Dry-heat sterilization

Question 16

What is the most effective heat sterilization method?

Answer 16

Moist-heat sterilization.

Question 17

Why is moist-heat sterilization effective?

Answer 17

It penetrates cells better than dry heat does (autoclaves).

Question 18

What is pasteurization?

Answer 18

Used to kill pathogens and reduce the number of microbes that cause food spoilage.

Question 19

What are the two types of pasteurization?

Answer 19

High temperature -> longer time at lower heat, refrigerated after opening.
Ultra-high temperature -> very little time, airtight containers for 90 days without refrigeration.

Question 20

What does refrigeration do for microbial growth?

Answer 20

Slows microbial growth; freezing stops growth, killing some organisms.

Question 21

How are lab and medical specimen stored?

Answer 21

May be frozen on dry ice or at ultra-low temperatures.

Question 22

How is pressure related to microbes?

Answer 22

High-pressure processing can be used to kill microbes in food.

Question 23

What does hyperbaric oxygen therapy do?

Answer 23

Increases oxygen saturation, has also been used to treat certain infections.

Question 24

How is desiccation accelerated?

Answer 24

Through the addition of salt or sugar, which decreases water activity in foods.

Question 25

What is lyophilization?

Answer 25

Combines cold exposure and desiccation for the long-term storage of foods and laboratory materials, but microbes remain and can be rehydrated.

Question 26

What is ionizing radiation?

Answer 26

An effective way to sterilize heat-sensitive and packaged materials.
- gamma radiation

Question 27

What is nonionizing radiation?

Answer 27

Unable to penetrate surfaces but is useful for surface sterilization.
- ultraviolet light

Question 28

What is HEPA filtration?

Answer 28

HEPA filtration is commonly used in hospital ventilation systems and biological safety cabinets in laboratories to prevent transmission of airborne microbes.

Question 29

What is membrane filtration?

Answer 29

Commonly used to remove bacteria from heat-sensitive solutions.

Question 30

What are phenolics?

Answer 30

Stable, long acting disinfectants that denature proteins and disrupt membranes.

Question 31

What are phenolics found in?

Answer 31

Commonly found in household cleaners, mouthwashes, and hospital disinfectants, and are also used to preserve harvested crops.

Question 32

How do heavy metals kill microbes?

Answer 32

They kill microbes by binding to proteins, thus inhibiting enzymatic activity.

Question 33

What are some halogens used for disinfection?

Answer 33

Fluorine
Chlorine compounds, including sodium hypochlorite, chloramines, and chlorine dioxide, water disinfection
Iodine, in both tincture and iodophor forms and an effective antiseptic.

Question 34

How do alcohols act as antiseptics?

Answer 34

Denature proteins and disrupting membranes. They tend to be bactericidal and fungicidal but may also be viricidal for enveloped viruses only.

Question 35

What do surfactants do?

Answer 35

Lower the surface tension of water to create emulsions that mechanically carry away microbes. Soaps are long-chain fatty acids, whereas detergents are synthetic surfactants.

Question 36

What do bisbiguanides do?

Answer 36

Bisbiguanides disrupt cell membranes, causing cell contents to gel.

Question 37

What are chlorhexidine and alexidine used for?

Answer 37

Surgical scrubs, for handwashing in clinical settings, and in prescription oral rinses.
Chlorhexidine is bacteriostatic at lower concentrations and bactericidal at higher concentrations.

Question 38

What do alkylating agents do?

Answer 38

Effectively sterilize materials at low temperatures but are carcinogenic and may also irritate tissue.

Question 39

What do peroxygens do?

Answer 39

They are strong oxidizing agents that produce free radicals in cells, damaging their macromolecules. they are environmentally safe and are highly effective disinfectants and antiseptics.

Question 40

How are chemical disinfectants grouped?

Answer 40

High level germicides, intermediate level germicides, low level germicides.

Question 41

What do high level germicides do?

Answer 41

Kill vegetative cells, fungi, viruses, and endospores, and can ultimately lead to sterilization.

Question 42

What do intermediate level germicides do?

Answer 42

Cannot kill all viruses and are less effective against endospores.

Question 43

What do low level germicides do?

Answer 43

Kill vegetative cells and some enveloped viruses but are ineffective against endospores.

Question 44

What is the disk-diffusion method?

Answer 44

Used to test the effectiveness of a chemical disinfectant against a particular microbe.

Question 45

What is the use-dilution test?

Answer 45

Determines the effectiveness of a disinfectant on a surface. In-use tests can determine whether disinfectant solutions are being used correctly in clinical settings.