Exam 3

Question 1

List the four outcomes of microbial control

Answer 1

Sterilization
Disinfection
Decontamination
Antisepsis

Question 2

Define Bactericide

Answer 2

Chemical that destroys vegetative bacteria but not endospores

Question 3

Define Bacteristatic

Answer 3

Chemical agents that prevent the growth of bacteria

Question 4

Define Antiseptic

Answer 4

Chemical agents applied directly to exposed body surfaces to prevent vegetative pathogens

Question 5

List the 4 common cellular targets of antimicrobials

Answer 5

Cell wall
Cytoplasmic Membrane
Cellular Synthesis
Proteins

Question 6

Contrast the antimicrobial effects of high and low tempartures

Answer 6

Elevated temperatures are microbicidal

Lower temperatures are microbistatic

Question 7

Contrast moist and dry heat as a means microbial control

Answer 7

Moist Heat: operates at lower temps and shorter exposure times to achieve the same effectiveness as dry heat. Microbicidal effect is the denaturation of proteins. Moist heat faster that dry heat, but dry heat can get hotter if necessary.

Dry Heat: Dehydrates the cell, removing water necessary for metabolic reactions. Denatures proteins. At vert high temps, oxidizes cells, burning them to ashes.

Question 8

Describe Moist Heat Methods: Boiling Water

Answer 8

Simple
Won’t kill all vegetative cells
Requires at least 30 minutes

Question 9

Describe Moist Heat Methods: Pasteurization

Answer 9

About 70 C for 15 seconds
Won’t kill endospores
Won’t kill thermodurics
Faster and better at killing that boiling water, preserves integrity of food

Question 10

Describe Moist Heat Methods: Autoclaving

Answer 10

True Sterilization
Steam can heat above 100 C as pressure rises.
10-40 mins at 121 C

Question 11

Describe Dry Heat Methods: Incineration

Answer 11

Burn everything to ash
Applies to limited materials
1000s of degrees C

Question 12

Describe Dry Heat Methods: Hot-Air Oven

Answer 12

Slightly easier that autoclave
Evaporates liquids
150-180 C for 2-4 hrs

Question 13

Describe the effects the cold has on microbes

Answer 13

Slows growth in food processing

Some microbes are preserved long term in very cold temperatures

Question 14

Describe the effects desiccation has on microbes

Answer 14

Vegetative cells directly exposed to normal room temperatures gradually become dehydrated
Some microbes are killed by desiccation; many others are not killed and some are preserved

Question 15

Describe Radiation Methods: Ionizing Radiation (Gamma and X-Rays)

Answer 15

Effective at destroying all life
Dangerous for living tissue
Penetrates solid surfaces
Doesn’t transfer to food

Question 16

Describe Radiation Methods: Nonionizing Radiation (UV Rays)

Answer 16

Not as penetrative, limiting it’s use

Effective at 260 nm at long time periods

Question 17

Describe Filtration Methods: Filtration

Answer 17

Used to prepare liquids that cannot withstand heat such as serum, blood products, vaccines, drugs, IV fluids, enzymes, and media
Alternative method for decontaminating milk and beer without altering their flavor
Important step in water purification
Unable to remove soluble molecules (toxins) that can cause disease
High-efficiency particulate air (HEPA) filters are used in hospital rooms and sterile rooms

Question 18

Describe Filtration Methods: Osmotic Pressure

Answer 18

Adding large amounts of salt or sugar to foods creates a hypertonic environment for bacteria, causing plasmolysis
Pickling, smoking, and drying foods have been used for centuries to preserve foods
Osmotic pressure is never a sterilizing technique