Micro Exam-2 Ch. 7

Question 1

Sterilization

Answer 1

Removing and destroying all living microorganisms

Question 2

Disinfection

Answer 2

Destroying harmful microorganisms

Question 3

Sanitization

Answer 3

Lowering microbial counts to safe public health levels

Question 4

Degerming

Answer 4

Mechanical removal of microbes from a limited area

Question 5

Antisepsis

Answer 5

Destroying harmful microorganisms from living tissue

Question 6

Biocide/germicide

Answer 6

Treatments that kill microbes

Question 7

Bacteriostatic

Answer 7

Inhibiting, not killing, bacteria

Question 8

Sepsis

Answer 8

From the Greek for decay or putrid, refers to bacterial contamination

Question 9

Asepsis

Answer 9

Absence of significant contamination

Question 10

-cital

Answer 10

killing organism

Question 11

-static

Answer 11

inhibiting growth

Question 12

When microorganisms are heated or treated with Antimicrobial agent they usually die at

Answer 12

a constant rate

Question 13

Effectiveness of treatment for microbes depends on

Answer 13

• Number of microbes
• Environment (organic matter, temperature, biofilms)
• Nature of medium (fat, proteins protect)
• Time of exposure
• Microbial characteristics

Question 14

Actions of Microbial Control Agents

-Alteration of membrane permeability

Answer 14

 Damages lipids or proteins of the plasma membrane
 Interrupt nutrient exchange, leaks cellular contents
 Interferes with the growth of the cell

Question 15

Actions of Microbial Control Agents

-Damage to proteins (enzymes)

Answer 15

 Heat or chemicals damage structural bonds

 Denature proteins

Question 16

Actions of Microbial Control Agents

-Damage to nucleic acids

Answer 16

 Damage to DNA and RNA effects cell replication and other metabolic functions

Question 17

Actions of Microbial Control Agents

Answer 17

• Alteration of membrane permeability
• Damage to proteins (enzymes)
• Damage to nucleic acids

Question 18

Moist heat (Boiling, steam)

Answer 18

denatures proteins/enzymes

Question 19

Dry heat (Flaming, Incineration, Hot-air)

Answer 19

– Kills by Oxidation

Question 20

• Steam under pressure

Answer 20

(Autoclave; temp above boiling water): Reliable sterilization

Question 21

• Autoclave:

Answer 21

steam under pressure
100 (0),110 (5), 116 (10), 121 (15), 126 (20), 135C (30 psi)
121C at 15 psi for 15 min
Kills all organisms and endospores
Steam must contact the item's surface

Question 22

Time is variable during sterilization depends on

Answer 22

size of glassware ect.

Question 23

Pasteurization

Answer 23

reduces spoilage organisms and pathogens

Question 24

Pasteurization reduces spoilage organisms and pathogens

Answer 24

• Mild heat treatment- Use mild heat treatment to kill pathogens and organisms-MILK
• Thermoduric organisms survive
• Dairy industry: Alkaline phosphotase test-APS

Question 25

Pasteurization- Low temperature long time (LTLT):

Answer 25

63 degree C for 30 mins

Question 26

Pasteurization- High-temperature short-time (HTST): also known as FLASH Pasteurization

Answer 26

72C for 15 sec

Question 27

Pasteurization- Ultra-high-temperature (UHT):

Answer 27

140C for 4 sec

Question 28

Differences can be expressed in terms of:

Answer 28

Thermal death point (TDP)
Thermal death time (TDT)
Decimal reduction time (DRT, D-value)

Question 29

Thermal death point (TDP):

Answer 29

lowest temperature at which all cells in a liquid culture are killed in 10 min

Question 30

Thermal death time (TDT):

Answer 30

minimal time for all bacteria in a liquid culture to be killed at a particular temperature

Question 31

Decimal reduction time (DRT, D-value)

Answer 31

Used to express bacterial heat resistance Minutes to kill 90% of a population at a given temperature-
D-value is always represented in minutes
THIS WILL BE ON TEST

Question 32

Filtration

Answer 32

• Passage of a liquid or gas through a screenlike material
• Used for heat-sensitive materials
Eg: some culture media, enzymes, vaccines, and antibiotics

Question 33

• High-efficiency particulate air (HEPA) filters- in BSL-3 & BSL-4

Answer 33

remove microbes >0.3 µm

Question 34

• Membrane filters

Answer 34

remove microbes >0.22 µm

Question 35

Low temperature

Answer 35

Provides bacteriostatic effect
• Refrigeration
• Deep-freezing

Question 36

High pressure

Answer 36

Denatures proteins

Question 37

Desiccation:

Answer 37

absence of water prevents metabolism
Microbes cannot grow or reproduce but remain viable for years
Lyophilization or freeze drying is an example

Question 38

Osmotic pressure:

Answer 38

uses salts and sugars to create hypertonic environment; causes plasmolysis (i.e., water leave the microbial cell)

Question 39

Ionizing radiation

Answer 39

(X rays, gamma rays, electron beams)
• Shorter wavelength (<1 nm)
• Ionizes water to create reactive hydroxyl radicals (ROS)
• Damages DNA by causing lethal mutations

Question 40

Nonionizing radiation

Answer 40

• UV (270 nm) –Germicidal lamp

* Damages DNA by creating thymine dimers which inhibit correct replication

Question 41

Microwaves

Answer 41

kill by heat; not especially antimicrobial

Question 42

Chemical agents

Answer 42

• Used for control the growth of microbes on both living tissue and inanimate objects
• Sterility levels varies depending on chemical agent
• Selection of suitable agent is key

Question 43

1. Use-Dilution Tests (AOAC standard)

Answer 43

• Metal or glass cylinders (8 mm x 10 mm) are dipped in test bacteria and dried
• Cylinders are placed in disinfectant for 10 min at 20C
• Cylinders are transferred to culture media to determine whether the bacteria survived treatment