Chapter 12: Sterilization And Disinfection

Question 1

Sterilization

Answer 1

Killing and removing every microbes on the surface

Question 2

Disinfection

Answer 2

Reduce microbes numbers to a point where little to no risk of infection

Question 3

Disinfectants

Answer 3

Used on inanimate objects/ surfaces

- bleach

Question 4

Antiseptics

Answer 4

Used on living tissue

- ex. Hand sanitizer, mouth wash

Question 5

Sanitizer

Answer 5

Chemical agent typically used on food handling equipment and eating utensils

Question 6

Germicide

Answer 6

Agent capable of killing microbes rapidly

Question 7

Bactericide

Answer 7

Bacteria killing agent, usually not spores

Question 8

Viricide

Answer 8

Agent that inactivated viruses

Question 9

Fungicide

Answer 9

Agent that kills fungi

Question 10

Sporocide

Answer 10

Agent that kills bacterial endospores or fungal spores

Question 11

Controlling microbial growth

Answer 11

Proportional death rates: definitive proportion of orgs will die in a given interval
Sterilization time: it’s faster to sterilize with fewer orgs present
Role of organic matter: can reduce effectiveness of chemicals
Microbial susceptibility: certain methods work better against different microbes

Question 12

Potency of chemical agents

Answer 12

Time
Temperature
pH
Concentration

Question 13

Bactericidal

Answer 13

Kills all bacteria

Question 14

Bacteriostatic

Answer 14

Controls bacteria (temporarily inhibits growth

Question 15

Phenol coefficient

Answer 15

(Carbolic acid) Compares various chemicals to phenol in effectiveness

Question 16

Filter paper method

Answer 16

Look for inhibition of growth around filter disc (infused with chemical) on a lawn of bacteria

Question 17

Use dilution assay

Answer 17

Used to determine growth of bacteria at different dilutions/concentrations of chemical
- modified: over time

Question 18

Disinfectant selection criteria

Answer 18

Fast acting around organics
Nontoxic
Wide spectrum
Non-damaging to materials
Easy to prepare
Stable (hydrogen peroxide in brown bottle) 
Readily available
Inexpensive
No offensive odor

Question 19

Antimicrobial mechanisms of action

Answer 19

Effects on proteins: permanently or temporarily denatures proteins
Effects on membranes: may directly damage membrane, or surfactant reduces lipid surface tension (loosens membrane)
Effects on nucleus acids & metabolism: most dangerous, may block metabolic step (fermentation)
Virus susceptibilities: target nucleus acids and proteins

Question 20

Soaps and detergents

Answer 20

Effectiveness increases with scrubbing

Target: lipid membrane

Question 21

Acids/alkalis

Answer 21

Affect pH
Target: denature proteins, prevent metabolic processes
- acids used as preservatives

Question 22

Heavy metals

Answer 22

Target: denature proteins

• silver nitrate drops in newborn eyes prevent blindness
• mercury used in skin wounds

Question 23

Halogens

Answer 23

Target: denature proteins

• chlorine bleach
• iodine to disinfect skin

Question 24

Alcohols

Answer 24

Target: denature proteins & disrupt membranes

- rubbing alcohol & ethanol

Question 25

Phenolics

Answer 25

Target: denature proteins & disrupt membranes

• Lysol
• trichlosan

Question 26

Oxidizer

Answer 26

Target: disrupt proteins and membranes

- hydrogen peroxide is most effective in anaerobic environments like puncture wounds

Question 27

Alkylation agents

Answer 27

Target: disrupt proteins & damage nucleus acids

- formaldehyde

Question 28

Food dye

Answer 28

Can kill microbes, used as preservative

Question 29

Heat

Answer 29

Dry: oxidizes molecules.
- lab loop, bake glassware in oven
Moist: more effective/faster. Denatures proteins and disrupts membranes
- boiling, autoclave (sterilizes)
Pasteurization: heat liquid to reduce number of microbes & reduce spoilage
- not completely sterile

Question 30

Cold

Answer 30

Slow growth, doesn’t kill
Refrigeration (4c): prevents spoilage for a few days
Freezing (-20c): prevents spoilage for a few months
Drying(dedication): absence of water inhibits growth
Freeze drying(lysophiliation): dry material from a frozen state, preserves long term

Question 31

Radiation

Answer 31

UV: damages DNA
- some bacteria have repair mechanisms
Ionizing: damage DNA
- x rays and gamma rays
Microwave
Visible

Question 32

Sonication

Answer 32

Sound waves target membranes and nucleus acids

Question 33

Filtration

Answer 33

Great for heat sensitive medication

- water, air

Question 34

Osmotic control

Answer 34

Ex. Salt cured meat

- salt sucks water out of meat for preservation