Chapter 9 Learning Outcomes

Question 1

Sterilization

Answer 1

Removal or destruction of ALL microbes, including viruses and bacterial endospores, in or on an object. (To eradicate harmful microorganisms and viruses)

ex (Preparation of microbiological culture media and canned food)

Question 2

Disinfection

Answer 2

Use of physical or chemical agents known as disinfectants (ultraviolet light, heat, alcohol, and bleach), to inhibit or destroy microorganisms, especially pathogens. Does not remove all… and only on inanimate objects.

ex (Use of phenolics, alcohols, aldehydes, or soaps on equipment)

Question 3

Antisepsis

Answer 3

When a chemical, antiseptic, is used on skin or other tissue. It is a lower concentration but is similar to disinfectant.

ex (when giving a shot and cleaning skin with an alcohol swab)

Question 4

Degerming

Answer 4

The removal of microbes from a surface by scrubbing.

ex (wash hands, nurse prepares arm for injection)

Question 5

Sanitization

Answer 5

Process of disinfecting places and utensils used by the public to reduce the number of pathogenic microbes to meet accepted public health standards.

ex (washing tableware in scalding water in restaurants)

Question 6

Pasteurization

Answer 6

Heat kills pathogens and reduces the number of spoilage microorganisms in food and beverages.

ex (Pasteurized milk and fruit juices)

Question 7

Compare the effects of static/stasis versus cidal/cide control agents on microbial growth.

Answer 7

-static: a chemical or physical agent INHIBITS microbial metabolism and growth but does not kill microbes (refrigerator)

-cidal: Agents that DESTROY or permanently inactivate a particular type of microbe. (germicides)

Question 8

Define microbial death rate and describe its significance in microbial control.

Answer 8

Microbial Death: The permanent loss of reproductive ability under ideal environmental conditions.

Significance: A broth becomes sterile when all the cells are dead. Die logarithmically

Question 9

aseptic

Answer 9

free from contamination from viruses/bacteria/fung

Question 10

Describe how antimicrobial agents act against cell walls, cytoplasmic membranes and nucleic acids.

Answer 10

Cell walls: Prevents cell wall from stopping the cell from bursting when osmosis occurs.

Cytoplasmic membranes: Allows cellular contents to leak out with causes the cell to die.

Proteins: Causes proteins shape to change by breaking the hydrogen and disulfide bonds which denatures the protein.

Nucleic Acids: Destroys nucleic acids which will produce fatal mutations.

Question 11

List factors to consider in selecting a microbial control method.

Answer 11

1. Site to be treated
2. Relative susceptibility of Microorganisms
3. Environmental Conditions

Question 12

Identify the three most resistant groups of microbes and explain why they are
resistant to many antimicrobial agents.

Answer 12

1. Bacterial endospores: Endospores of Bacillus and Clostridium can survive environmental extremes of temperature, acidity, and dryness.
2. Species of mycobacteria: Cell walls contain a large amount of a waxy lipid which allows them to survive drying and protects them from most water-based chemicals.
3. Cysts of protozoa: Cyst’s wall prevents entry of most disinfectants, protects against drying, and shields against radiation and heat.

Question 13

Discuss the environmental conditions that can influence the effectiveness of
antimicrobial agents.

Answer 13

Temperature and pH. Higher temperatures cause chemicals to react faster and acidic conditions enhance the antimicrobial effect of heat

Question 14

List and describe the five types of physical methods. Be sure to know the mode of
action and the representative uses of each physical method.

Answer 14

1. Exposure of the microbes to extremes of heat and cold
2. Desiccation
3. Filtration
4. Osmotic pressure
5. Radiation

Question 15

Heat related methods: Discuss the advantages and disadvantages of using moist
heat in an autoclave and dry heat in an oven for sterilization

Answer 15

*moist heat in an autoclave
-moist heat(commonly used to disinfect, sanitize, sterilize, and pasteurize) kills cells by denaturing proteins and destroying cytoplasmic membranes
-more effective in microbial control than dry heat bc water is a better conductor of heat than air

-The disadvantage is it takes longer for large volumes of liquids or solids bc it takes more time for heat to penetrate

*dry heat in an oven
-used for substances such as powders and oils that cannot be sterilized by boiling or w/ steam or for materials that can be damaged by repeated exposure to steam
-effective bc it denatures proteins and fosters the oxidation of metabolic and structural chemicals

-The disadvantage is it requires higher temps for longer times than moist heat bc dry heat penetrates more slowly

Question 16

Explain the uses of Bacillus endospores in sterilization techniques.

Answer 16

Used to test if something is sterile or not. The endospores are impregnated into tape with is aseptically inoculated into sterile broth. If no growth appears, the original material is sterile.

Question 17

Explain the importance of pasteurization and describe three different pasteurization
methods

Answer 17

Used to destroy microorganisms and pathogens in liquids that cause spoilage.
1. Batch Method: 63”C for 30 min.
2. Flash Pasteurization: 72”C for 15 second
3. Ultra-high-temperature Pasteurization: 135”C for 1 second

Question 18

Refrigeration and Freezing: Describe the use and importance of refrigeration and
freezing in limiting microbial growth. Is refrigeration bactericidal or bacteriostatic?

Answer 18

Slow down chemical reactions and decrease microbial metabolism, growth, and reproduction.

Refrigeration: halts the growth of most pathogens.

Freezing: slow freezing (ice crystals puncture cell membranes) are more efficient than quick freezing.

Question 19

Desiccation and Lyophilization: Compare and contrast desiccation and lyophilization.
Are these methods bactericidal or bacteriostatic?

Answer 19

Desiccation - Drying inhibits growth because of the removal of water. (drying)

Lyophilization- combines freezing and drying and is used for the long-term preservation of microbial cultures. (freeze-drying)

bacteriostatic

Question 20

Filtration: Describe the use of filters for disinfection and sterilization.

Answer 20

Filters have pores that allow smaller particles to pass through while trapping and separating larger microbes The particles it is designed to trap are cells or viruses. Scientist can use this to estimate the number of microbes by comparing the viruses trapped to the volume passed through the filter.

Question 21

Osmotic Pressure: Discuss the use of hypertonic solutions in microbial control

Answer 21

Enzymes are fully functional only in aqueous environments; therefore, removing water from osmotic pressure inhibits bacteria’s cellular metabolism.

Question 22

Radiation: Differentiate ionizing radiation from nonionizing radiation as they relate
to microbial control. Can they achieve sterilization, disinfection, or both?

Answer 22

ionizing: shorter than 1nm in wavelength
electron beams, gamma rays, some xrays
ions disrupt hydrogen bonding and oxidize double covalent bonds and create hydroxyl radicals

non-ionizing: wavelength greater than 1nm
excites electrons, causing them to make new covalent bonds affects 3D structure of proteins and nucleic acids

Question 23

Chemical Methods: Compare and contrast nine major types of antimicrobial chemicals and discuss the positive and negative aspects of each. Be sure to know the mode of action and the representative uses of each physical method.

Answer 23

1. phenols: Denatures proteins and disrupts cell membranes (middle to low)
2. alcohols: Denature proteins and disrupt cell membranes (middle)
3. halogens: denature proteins (middle)
4. oxidizing agents: denature proteins by oxidation (High)
5. surfactants: Decrease surface tension of water and disrupt cell membranes (Low)
6. heavy metals: Denature proteins (Low)
7. aldehydes: denature proteins (High)
8. gaseous agents: denature proteins (High)
9. enzymes: denature proteins (High against target substrate)

Question 24

Phenol and Phenolic: Distinguish between phenol and the types of phenolics and
discuss their action as antimicrobial agents

Answer 24

Phenol (carbolic acid) - Denatures proteins and
disrupts cell membranes

Uses: Original surgical antiseptic; now
replaced by less odorous and injurious
phenolics

Phenolics (chemically altered phenol; bis phenolics are composed of a pair of linked phenolics) - Denature proteins and disrupt cell membranes.

Uses: Disinfectants and antiseptics

Question 25

Halogens: Discuss the types and uses of halogens-containing antimicrobial agents.

Answer 25

Halogens (iodine, chlorine, bromine, and
fluorine) - Denature proteins

Uses: Disinfectants, antiseptics, and water
purification

Question 26

Oxidizing Agents: Describe the use and action of oxidizing agents in microbial control.

Answer 26

Oxidizing Agents - Denature proteins by
oxidation

Uses: Disinfectants, antiseptics for deep wounds, water purification, and sterilization of food processing and medical equipment

Question 27

Surfactants: Define surfactants and describe their antimicrobial action

Answer 27

Surfactants (soaps and detergents) - Decrease surface tension of water and disrupt cell membranes

Uses: Soaps: degerming; detergents:
antiseptic

Question 28

Heavy Metals: Define heavy metals ions, give several examples, and describe their use in microbial control.

Answer 28

Heavy Metals - Relatively high-density metals, such as mercury, arsenic, zinc, silver, and copper, that are toxic at low concentrations. Heavy-metal ions are antimicrobial because they combine with sulfur atoms in molecules of cysterine, an amino acid.

Uses: Fungistats in paints; silver nitrate
cream: surgical dressings, burn
creams, and catheters; copper: algicide
in water reservoirs, swimming pools,
and aquariums

Question 29

Aldehydes: Compare and contrast formaldehyde and glutaraldehyde as antimicrobial agents.

Answer 29

-Formaldehyde: is a gas, highly reactive chemical, used for embalming & to disinfect hospital rooms

-Glutaraldehyde: is a liquid, less irritating but more expensive

Work in microbial control by cross-linking organic functional groups

Question 30

Gaseous Agents: Describe the advantages and disadvantages of gaseous agents of
microbial control.

Answer 30

These gases are used in close chambers for heart-lung machines, sutures, plastic laboratory ware, and mattresses. They are ethylene oxide, propylene oxide, and beta-propiolactone.

The advantage is that these gases penetrate paper and plastic wraps and diffuse every crack. Over time, they denature proteins and DNA by cross-linking organic functional groups, thereby killing everything they come into contact with.

The disadvantage is that they are highly explosive, extremely poisonous, and carcinogenic, and hospital workers have to flush equipment extensively with air to remove all traces of the gases.

Question 31

Enzymes: Describe the use of enzymes to remove most bacteria from food and to
remove prions from medical instruments.

Answer 31

Food processors use Lysosome to reduce the number of bacteria in cheese and some vintners. Prionzyme is used on medical instruments to rid them of prions.

Question 32

Antimicrobial drugs: describe three general types of antimicrobial drugs and their use in the environmental control of microorganisms.

Answer 32

-Antibiotics, semi-synthetics, and synthetics are used for environmental control.

-Antibiotics are antimicrobial chemicals produced naturally by microorganisms

-Semi-synthetics are chemically modified antibiotics

-Synthetics are scientist developed