Chapter 9- Controlling Microbial Growth

Question 1

Static

Answer 1

inhibits growth but does not kill the microbe

Question 2

Cidal

Answer 2

kills the microbe

Question 3

Sterilization

Answer 3

The removal of all microorganisms, including endospores

Question 4

Disinfection

Answer 4

A chemical treatment to kill/inhibit growth on inanimate objects

Question 5

Degerming

Answer 5

The mechanical removal of most of the microorganisms in a limited area by scrubbing

Question 6

Sanitation

Answer 6

Reducing the # of pathogens

Question 7

Aseptic

Answer 7

Free of contamination

Question 8

2 ways the microbial control agents kill or inhibit the growth of microorganisms:

Answer 8

1. Alteration of cell walls/plasma membrane
2. Damaging proteins/DNA

Question 9

Alteration of cell walls/plasma membrane:

Answer 9

Disrupts osmosis and/or allows cellular contents to leak out

Question 10

Damaging proteins/DNA

Answer 10

Denatures the shape of proteins

Question 11

Factors to select the most appropriate antimicrobial:

Answer 11

• Harmless to humans
• Effectiveness
• Susceptibility of microbe (the bacteria must be susceptible to it)

Question 12

Physical Methods of Microbial control

Answer 12

1. Moist Heat
2. Dry Heat
3. Low Temperature
4. Desiccation
5. Filtration
6. Osmotic Pressure
7. Radiation

Question 13

Moist Heat

Answer 13

Denatures proteins and disrupts cell membranes

Question 14

Methods within moist heat

Answer 14

• Boiling
• Autoclaving
• Pastureization

Question 15

Boiling

Answer 15

• Type of moist heat sterilization
• Kill pathogens and almost all viruses in 10 min
• Less effective on destroying endospores

Question 16

At sea level, water boils at

Answer 16

100 C

Question 17

Autoclaving

Answer 17

• Uses pressure per square inch (psi)
• Used to sterilized culture media and surgical equipment
• Gets rid of endospores

Question 18

Pasteurization

Answer 18

• Kills pathogenic bacteria and most nonpathogens
• Many heat-resistant bacteria survive pasteurization but are nonpathogenic
• NOT sterilization

Question 19

Dry Heat

Answer 19

Requires higher temps for often longer time periods compared to moist heat

Question 20

Types of dry heat:

Answer 20

• Direct Flaming
• Hot-air Sterilization
• Incinerator

Question 21

Direct Flaming

Answer 21

• Used to sterilize inoculating loops and needles
• ex: bunsen burner

Question 22

The Bunsen burner achieves a temp of

Answer 22

1500 C

Question 23

Hot-air Sterilization

Answer 23

• Placed in oven for 2 hours
• Used to sterilize empty glassware

Question 24

Incinerator

Answer 24

Can achieve temperatures of 850C for as little as 2 seconds

Question 25

Low Temperature & important exception

Answer 25

- Refrigeration temperatures will slow bacterial growth and metabolism - Bacteriostatic effect (will not kill, only inhibit) Important exception: *Listeria monocytogenes*

Question 26

Desiccation

Answer 26

- Condition where microorganisms cannot grow/reproduce in the absence of water - When water is available again, they can resume their growth - Bacteriostatic (will not kill, only inhibits) - Lyophylization

Question 27

Lyophilization

Answer 27

(freeze-drying), used for long-term preservation of microbial cultures

Question 28

Filtration

Answer 28

- Removal of microorganisms by passage through pores - Pores need to be small enough to hold back microbes - Purpose of wearing face masks during surgery and for HEPA filters

Question 29

Osmotic Pressure

Answer 29

- High concentration of salt and sugar in food to inhibit growth - Microbial cells in hypertonic solution lose water and cannot grow/multiply

Question 30

Radiation: two types

Answer 30

Ionizing radiation Nonionizing radiation

Question 31

Ionizing radiation

Answer 31

- Ejects electrons - Creates **hydroxyl radicals** - Good for controlling growth on gloves, syringes, meat/food

Question 32

Nonionizing radiation

Answer 32

- Excites electrons - **UV light damages the DNA** - Good for surface objects

Question 33

The mechanism of action for both types of radiation is the

Answer 33

damage to DNA

Question 34

Chemical Methods of Microbial control and types

Answer 34

1. Phenolics 2. Halogens 3. Alcohols 4. Heavy Metals 5. Surfactants 6. Oxidizing Agents

Question 35

Phenolics

Answer 35

- Denatures proteins and disrupts the cell membranes - Triclosan: phenol and phenolics - Found in garbage and diapers

Question 36

Halogens

Answer 36

- Damages proteins with denaturation - Iodine (oldest/most effective antispetic) - Chlorine (disinfects water, present in bleach) - Flouride (toothpaste) - Bromine (hot tubs)

Question 37

Alcohols

Answer 37

- Kill bacteria and fungi but not endospores - Denatures proteins and disrupts plasma membrane

Question 38

Heavy Metals

Answer 38

- Denatures proteins - Exs: Zinc, Mercury, Copper, Silver

Question 39

____ is often found in ___ creams

Answer 39

Silver is often found in burn creams

Question 40

Surfactants-3 types

Answer 40

Soap Acid-anionic detergents Cationic detergents

Question 41

Surfactants-mechanism of action

Answer 41

Disrupts cell membrane

Question 42

Soap

Answer 42

- Good degerming agents - Doesn't really kill/inhibit growth

Question 43

Acid-anionic detergents

Answer 43

- Carries negative charge - Nontoxic and non-corrosive to humans - Fast-acting - Found in laundry detergent

Question 44

Cationic detergents

Answer 44

- Carries positive charge - Most widely used cationic detergents are Quats, which disrupt the cell membrane and is bacteriocidal except for endospores

Question 45

Other than endospores, what else can Quats not destroy and why?

Answer 45

Mycobacteria due to the waxy cell membrane

Question 46

Oxidizing Agents

Answer 46

- Damages cellular components of microbe - Ex: Hydrogen peroxide

Question 47

Hydrogen peroxide

Answer 47

- Not a good antiseptic for open wounds due to the enzyme catalase - Good disinfectant for nonliving objects