Module 4.3

Question 1

Controlling Microbial Growth

Answer 1

Sterilization
Disinfection
Sanitization
antisepsis
Cleaning, degerming, decontamination, preservation

Question 2

Physical methods of Controlling Microbial Growth - 4

Answer 2

Heat treatment
Irradiation
Filtration
Mechanical removal

Question 3

a chemical method in controlling microbial growth. (1)

Answer 3

Antimicrobial Chemicals

Question 4

refers to killing or complete elimination of all viable microorganisms. This uses agents - sterilants or sterilizing agents (e.g ethylene oxide, steam under pressure.

Answer 4

Sterilization

Question 5

refers to the elimination or reduction of pathogens from inanimate objects or surfaces. It uses agents - disinfectants (e.g alcohol, formaldehyde, chlorine).

Answer 5

Disinfection

Question 6

refers to the reduction of microbial populations to levels considered safe by public health standards (e.g iodine, chlorine)

Answer 6

sanitization

Question 7

refers to the prevention of infection in living tissues using chemicals (e.g iodine, alcohol, hydrogen peroxide)

Answer 7

antisepsis

Question 8

is considered to be one of the most useful methods of microbial control. It is reliable, safe, relatively fast, and inexpensive. It is used to sterilize or decrease microbial numbers. It can be in the form of moist or dry.

Answer 8

heat

Question 9

refers to the temperature that kills all bacteria in a 24-hour old broth culture at neutral pH in 10 minutes.

Answer 9

Thermal Death Point

Question 10

refers to the time required to kill all bacteria in a particular culture at a specified temperature

Answer 10

Thermal Death Time

Question 11

is a form of heat that consists of efficient penetrating properties. It destroys microorganisms by irreversibly coagulating their proteins. It can be through boiling, pasteurization, or pressurized steam.

Answer 11

Moist Heat

Question 12

requires to be at 100°C. At this temperature, most bacteria are destroyed and some viruses are inactivated. This also kills vegetative cells and eukaryotic spores within 10 minutes.

Answer 12

Boiling

Question 13

refers to the use of brief heat treatment (moderately high temperature) to reduce the number of spoilage organisms and kill pathogens (e.g Salmonella, Mycobacterium).
This process is also used to make wine, beer, vinegar, milk, juices.
It significantly reduces the number of heat-sensitive microorganisms; does not significantly alter the quality of food.
It increases the shelf-life of food and protects consumers.

Answer 13

Pasteurization

Question 14

What are the four methods under pasteurization? (4)

Answer 14

1. Low-Temperature Holding (LTH) - 62.8°C for 30 minutes
2. High-Temperature-Short-Time (HTST) Method - milk: 72°C, 15 seconds (flash method); ice cream: 82°C, 20 seconds
3. Ultra-High-Temperature (UHT) Method - 140-150°C (several seconds); involves complex cooling processes; e.g boxed juices, coffee creamers.
4. Mechanical Pasteurization (non-food) - e.g hospital anesthesia mask: 80°C, 15 minutes.

Question 15

____ include using pressure cookers and autoclaves. This can be achieved by heating water in an enclosed vessel that achieves temperatures above 100°C. It can also be in 15 minutes, 15 psi, at 121°C (kills endospores and disrupts viruses’ nucleic acids).
Only items that can be penetrated by steam and withstand heat and moisture can undergo this treatment (e.g surgical instruments, microbiological media, reusable glassware, microbial cultures, and biohazards before disposal).
This also ensures Clostridium botulinum endospores are destroyed.

Answer 15

Pressurized Steam

Question 16

refers to fractional steam sterilization or intermittent sterilization. This is for materials that can be destroyed at more than 100°C. This puts organisms exposed to 90-100°C for 30 minutes for 3 consecutive days.
This is used for some canned foods and laboratory media.

Answer 16

Tyndallization (Nonpressurized Steam)

Question 17

is not as efficient as wet heat (lower penetrating properties). It requires longer times and higher temperatures. It is only used for metal objects and glassware. It can be achieved by using an oven or an open flame (incineration).

Answer 17

Dry Heat

Question 18

uses dry heat; oxidizes cell components to ashes.

Answer 18

Incineration

Question 19

uses dry heat; oxidizes cell components and irreversibly denatures proteins. It is used to sanitize Petri dishes and glass pipettes. It is by default at 170-180°C for 1 hour. It can be used on powders, oils, or anhydrous materials.

Answer 19

Dry Heat Oven/Hot Air

Question 20

What are some low-temperature methods? (2)

Answer 20

Refrigeration
Freezing or Deep Freezing

Question 21

• 4-5°C; limited to a few days because bacteria and molds continue to grow still at low temperatures.

Answer 21

refrigeration

Question 22

• 0-95°C; used to preserve food in homes and food industries; slows the rate of chemical reactions in bacterial cells.

Answer 22

Freezing or Deep Freezing

Question 23

What are the two types of filtration methods? (2)

Answer 23

fluid and air filtration

Question 24

• remove organisms from heat-sensitive fluids.

Answer 24

Fluid Filtration

Question 25

high-efficiency particulate air (HEPA): remove from air nearly all microorganisms with diameter greater than 0.3 µm.

Answer 25

air filtration

Question 26

is used to preserve food (in the absence of water that inhibits the action of enzymes). It is also used to minimize the spread of infectious agents (e.g Treponema).

Answer 26

Drying/Desiccation

Question 27

is also referred to as lyophilization. It is the drying of material from a frozen state. It is for long-term preservation (e.g instant coffee, culture preservation).

Answer 27

Freeze-Drying

Question 28

causes plasmolysis of bacterial cells. It is said that high salt or sugar conc. creates a hyperosmotic medium, drawing water out of microorganisms.

Answer 28

increased osmotic pressure

Question 29

Radiation can be categorized into two: (2)

Answer 29

Ionizing
Non-ionizing

Question 30

• has enough energy to free electrons from the atoms or molecules they are attached to, and therefore ionizing them.

Answer 30

Ionizing Radiation

Question 31

• lacks the energy to break these same molecular bonds and cannot free electrons from atoms or molecules.

Answer 31

Non-ionizing Radiation

Question 32

are less reliable than heat; suitable for treating large surfaces and heat-sensitive items; some are non-toxic; can be used as preservatives (bacteriostatic).

Answer 32

Chemical Agents

Question 33

What are some examples of chemical agent? (8)

Answer 33

Alcohols
Aldehydes
Phenols or Phenolics
Halogens
Heavy Metals
Sterilizing Gases
Surface Active Agents or Surfactants
organic molecule/other (Hydrogen peroxide)

Question 34

coagulate enzymes and other essentials and damages lipid membranes. They are used as antiseptics for degerming or as disinfectants for treating instruments and surfaces (e.g 60-80% ethyl or isopropyl alcohol.

Answer 34

Alcohols

Question 35

inactivate proteins and nucleic acids (e.g glutaraldehyde, formaldehyde (formalin (aqueous 37% formaldehyde): kill most forms of microorganisms), orthopthaldehyde (OPA).

Answer 35

Aldehydes

Question 36

disrupts the cell membrane, denatures proteins, and inactivates enzymes. (e.g phenol, cresol, xylenon, triclosan).

Answer 36

Phenols/Phenolics

Question 37

oxidizes cell constituents (e.h iodine, chlorine).

Answer 37

Halogens

Question 38

denatures enzymes and essential proteins (e.g silver nitrate (prevents ophthalmic gonorrhoeae); copper sulfate (algicide); silver sulfadiazine (used on burns); merthiolate (disinfects skin mucous membranes).

Answer 38

Heavy Metals

Question 39

denatures protein; for heat-sensitive items (catheters, plastic Petri plates); e.g ethylene oxide, ozone, chlorine dioxide.

Answer 39

Sterilizing Gases

Question 40

include soaps and acid-anionic detergents; mechanical removal of microorganisms. Also included are cationic detergents, they disrupt the cell membrane and denature proteins.

Answer 40

Surface Active Agents or Surfactants

Question 41

inhibit microbial metabolism (e.g sorbic acid, benzoic acid, calcium propoionate) and are widely used in foods/cosmetics).

Answer 41

Organic Acids

Question 42

What is another oxidizing agent that can be used to control microbial growth?

Answer 42

Hydrogen Peroxide (oxidation of cell components)