Control of Microbial Growth

Question 1

What is BSL-1?

Answer 1

working with microbes that have the lowest risk for infection. They generally do not cause disease in healthy hosts.
- An example of a microbe that would be used in BSL-1 is E. coli.
- Few precautions are needed because they pose a low risk to both workers and the environment.

Question 2

What is BSL-2?

Answer 2

microbes that pose a moderate risk to lab workers and the environment. An example of a microbe in this level would be Staphylococcus aureus

Question 3

What is BSL-3?

Answer 3

microbes could potentially cause lethal infections and serious diseases. These microbes can infect an individual if inhaled.
- Examples of microbes in this category would be Mycobacterium tuberculosis and Bacillus anthracis.

Question 4

What is BSL-4?

Answer 4

microbes that are very contagious and quite dangerous. They can cause infections that have no treatments or vaccinations.
- An example would be the Ebola virus.

Question 5

What biosafety level do we work at in the BLC?

Answer 5

BSL-2

Question 6

What is sterilization?

Answer 6

completely kills or eliminates all vegetative cells, viruses, and endospores from the targeted item

Question 7

What is the aseptic technique?

Answer 7

method that maintains sterility as it prevents contamination of an item with microbes

Question 8

What is disinfection?

Answer 8

antimicrobial chemicals or heat are used to inactivate most microbes on the surface of an inanimate item
- reduces the microbial load, but it does not completely eliminate all microbes on the surface

Question 9

What is antisepsis?

Answer 9

an antimicrobial chemical is used to reduce the microbial load on tissue or skin.

Question 10

What is degerming?

Answer 10

gentle scrubbing of living tissue or the use of mild chemicals are used to significantly reduce microbial load
- Ex: hand washing.

Question 11

What is sanitizing?

Answer 11

antimicrobial chemicals or heat are used to reduce microbial load of a fomite
- reduces microbial load to levels that are safe for public health.

Question 12

What is a fomite?

Answer 12

inanimate objects that you could touch that could be involved in the process of transmission
- Ex: doorknobs, silverware

Question 13

What is cidal?

Answer 13

suffix that describes when a method can kill a target microbe

Question 14

What is static?

Answer 14

suffux used to describe a method that does not kill a microbe but instead, stops or inhibits their growth

Question 15

What is the prefix bacteri-?

Answer 15

describes bacteria

Question 16

What is the prefix viri-?

Answer 16

describes viruses

Question 17

What is the prefix fungi-?

Answer 17

describes fungi

Question 18

What is a microbial death curve?

Answer 18

used to measure the effectiveness of microbial control methods
- describes how well a certain protocol works by looking at the percentage of microbes that are killed in a population
- the number of live bacterial cells is plotted against time
- the D value shows the time it takes for the number of cells to decrease by 90%.

Question 19

What are methods that use heat?

Answer 19

incineration, oven, autoclave, boiling, and pasteurization

Question 20

What are dry-heat methods?

Answer 20

incineration and oven

Question 21

What are moist-heat methods?

Answer 21

autoclave, boiling, and pasteurization

Question 22

What is incineration?

Answer 22

dry heat is applied at very high temperatures that destroy all microbes
- destroys all microbes, even prions, by burning
* used in a flaming loop or micro incinerator*

Question 23

What is dry-heat oven?

Answer 23

dry heat is applied for long periods of time at higher temperatures (170°C for 2 hours)
- dehydrate, desiccate, alter membranes, and denature proteins
* sterilize glassware and some lab equipment*

Question 24

What is autoclave?

Answer 24

high temperature and pressure are used to sterilize items
- alters membranes and denatures proteins
- can kill endospores, viruses, and vegetative cells
- considered the most effective method of sterilization
* sterilize lab equipment and microbiological media*

Question 25

What is boiling?

Answer 25

alters membranes and denatures proteins at 100°C.
- effective at killing vegetative cells and some viruses
- less effective at killing endospores
* used in cooking and when preparing certain lab media*

Question 26

What is pasteurization?

Answer 26

form of microbial control for food that is used in food preservation
- used to kill heat-sensitive pathogens in food products
- alters membranes and dentures proteins
- heat is used to reduce the number of microbes in a product or food
* used to prevent spoilage of foods like milk and honey*

Question 27

What is UHT?

Answer 27

food product is exposed to a temperature of 138° C for more than two seconds
- causes slight changes in the taste and smell of food, but it can be stored for longer periods without spoilage.

Question 28

What is refrigeration?

Answer 28

metabolism is inhibited or slowed
- does not kill cells
- temperatures of around 0°C to 7°C are used
helps to preserve food or lab materials

Question 29

What is freezing?

Answer 29

can stop metabolism and even kill microbes
- temperatures below -2°C are used
helps in the long-term storage of lab cultures and food

Question 30

What is pascalization (high-pressure processing)?

Answer 30

Being exposed to high pressure can kill many microbes
- can kill bacteria, molds, yeasts, viruses, and parasites in foods
used in food preservation as it helps extend shelf-life while also maintaining the food quality
- can kill vegetative cells by protein denaturation, and it can cause cells to lyse, but endospores can survive under these pressures

Question 31

What is dessication

Answer 31

uses dehydration or drying to preserve foods
- desiccation can control microbial growth by inhibiting metabolism
- does not kill all microbes or endospores.
It is used to make dried fruits or jerky

Question 32

What is ionizing radiation?

Answer 32

involves the exposure of microbes to X-rays or gamma rays
- alter the molecular structures of cells and damage their DNA
used to sterilize materials that cannot be autoclaved

Question 33

What is non-ionizing radiation?

Answer 33

involves the exposure of microbes to ultraviolet light
used for disinfection of surfaces in labs and the disinfection of water and air
- introduces thymine dimers that can lead to cell mutations

Question 34

What is HEPA filtration?

Answer 34

filters with a pore size that is small enough to capture and remove microbes such as endospores, many viruses, and bacterial cells as air flows through them
- effective at nearly sanitizing air
used in biosafety cabinets and operating rooms

Question 35

What is membrane filtration?

Answer 35

effective pore size used to remove microbes from liquid solutions
- sizes depend on the volume of solution that is being filtered
used to remove bacteria from heat-sensitive solutions. For instance, antibiotics and vitamins

Question 36

What are phenolics?

Answer 36

chemical disinfectant and antiseptic characterized by its phenol group
- the phenol group inhibits microbial growth as it denatures proteins and disrupts membranes.

Question 37

What are heavy metals?

Answer 37

kill microbes by binding to proteins
- this binding inhibits enzymatic activity
They are used as disinfectants and antiseptics

Question 38

What are halogens?

Answer 38

oxidize cellular components and destabilize macromolecules in cells

Question 39

What are alcohols?

Answer 39

used as disinfectants and antiseptics
- rapidly denatures proteins causing the inhibition of cell metabolism
- also disrupt membranes leading to the lysis of cells.

Question 40

What are surfactants?

Answer 40

these are used for degerming
- in soaps, detergents, and mouthwash
- lower the surface tension of water and create emulsions that help wash away microbes
- also disrupt cell membranes.

Question 41

What are bisbiguianides?

Answer 41

contains antiseptic properties
- disrupts cell membranes at low concentrations
- also causes congealing of intracellular contents at high concentrations

Question 42

What is chlorhexidine?

Answer 42

an important bisbiguanide
- disrupts cell membranes and is bacteriostatic at lower concentrations or bactericidal at higher concentrations.

Question 43

What are alkylating agents?

Answer 43

group of strong disinfectant chemicals that inactivate enzymes and nucleic acid by replacing a hydrogen atom in a molecule with an alkyl group.

Question 44

What is ethylene oxide? What is different about this chemical? What are advantages and disadvantages of this?

Answer 44

form of cold sterilization used for gaseous sterilization
- disadvantages: highly explosive and carcinogenic
- advantages: highly penetrating and can sterilize items within plastic bags

Question 45

What are peroxygens?

Answer 45

strong oxidizing agents that can be used as antiseptics or as disinfectants
- cause destabilization of cellular macromolecules
- also causes free radical formation in cells

Question 46

What are supercritical gases (supercritical CO2)?

Answer 46

penetrates cells and forms carbonic acid, lowering intracellular pH
- effective against vegetative cells and can kill endospores when it is combined with peracetic acid

Question 47

What are food preservation methods?

Answer 47

chemical preservatives can minimize spoilage in some foods and inhibit microbial growth
- decrease pH and inhibit enzymatic function and the synthesis of the cell wall.