Module 6 Control of Bacterial Growth EXAM 2

Question 1

Which types of organisms have least resistance to microbial control methods?

Answer 1

Most bacterial vegetative cells
Fungal spores
Enveloped viruses
Yeasts

Question 2

Which types of organisms have moderate resistance to microbial control methods?

Answer 2

Protozoan cysts
Naked viruses
Mycobacterium tuberculosis
Staphylococcus aureus- MRSA
Pseudomonas

Question 3

Which types of organisms have the most resistance to microbial control methods?

Answer 3

Endospores
Prions

Question 4

Sterilization

Answer 4

the destruction of all microbial life, used on inanimate objects (kills everything)

Question 5

Disinfection

Answer 5

destroys vegetative microbial life, reducing contamination on inanimate surfaces (disinfection and antisepsis can have some of the same chemical agents used for both)

Question 6

Antisepsis

Answer 6

destroys vegetative microbial life, reducing contamination on living surface

Question 7

Decontamination

Answer 7

the mechanical removal of most microbes from an animate or inanimate surface

Question 8

What is the method of action of detergents and soaps (surfactants)?

Answer 8

Disrupt cell membrane - interact with phospholipid membrane, poke holes in it so water can come in and cell will lyse
- They lose selective permeability
-Gram (-) is more susceptible

Effective against all bacteria
Effective against some viruses that have cell membrane-like structure (enveloped) - some have polar like heads and nonpolar like tails

Question 9

What is the method of action of heat, alcohol, acids, phenols, and heavy metals used to control microbial growth?

Answer 9

Certain agents can denature proteins; when denaturing a protein you disrupt the structure which effects the function

Question 10

What the general difference between dry vs. moist heat in terms of its effectiveness to control microbial growth? Dry heat:

Answer 10

Ignites and reduces microbes to ashes
Incineration on inoculating loops using a bunsen burner
Incineration and dry ovens: sterilizes
Used for heat resistant items that do not sterilize well with moist heat; such as glassware, metallic instruments - may use for something like an endoscopy bc it goes in sensitive area

Question 11

What is the general difference between dry vs. moist heat in terms of its effectiveness to control microbial growth? Moist heat:

Answer 11

Moist heat: lower temperatures, shorter exposure times
Autoclave: sterilizes
Pasteurization and boiling water: disinfectants

Question 12

What are the basic principles of how an autoclave works to control microbial growth and examples of its use?

Answer 12

Water goes into a gaseous state and causes pressure; pressure raises temperature of the steam; cell bursts apart denaturing any proteins that may be around, destroys the DNA
Kills all bacteria including endospores
Yields to 121 ºC - 15 psi for about 15-20 minutes
Used for heat sensitive materials, which steam is permeable - culture media

Question 13

What is the basic principles of how pasteurization works to control microbial growth and examples of its use?

Answer 13

Used to essentially disinfect, not sterilize
Used to disinfect beverages so it kills most microbes but retains the liquids flavor; so does not kill endospores but does kill bacteria that might cause us to become ill (ex: E. coli)
Kills microbes at about 70 ºC for 20-30 secs
May still be some bacteria (Lactobacillus) that is not harmful

Question 14

What are the effects of cold on microbial growth?

Answer 14

Bacteriostatic (static means that no microbes are killed but are essentially not reproducing)
Used to preserve food, media, cultures
Freezing will not kill of all microbes
May bring down level of microbial growth even more but still will not kill everything

Question 15

What are the basic differences between how ionizing vs. non-ionizing radiation work to control microbial growth? (give examples of each type of radiation)

Ionizing:

Answer 15

Ionizing radiation: very penetrating; when it hits DNA it ejects electrons, causing ions to form; ions cause breaks in the DNA
Examples: gamma rays, x rays
Ionizing radiation can be used for things like food products, medical instruments
Main advantages: speed, penetrating power, no heat
Typically used on non living things

Question 15

What is meant by desiccation?

Answer 15

To dry out, removal of water - this leads to metabolic inhibition
Virus and fungal spores can live in long periods of desiccation

Question 16

What is a pyrimidine dimer? How is it formed? Can it be fixed? If so, how?

Answer 16

A mutation
It is formed normally where there are two Thymies next to each other; UV light tends to break hydrogen bonds between the A and T on opposite ends…a covalent bond bond then forms between the two thymines next to each other
It can be fixed by a repair mechanism if it is not exposed for too long
If it is exposed for a long time this will cause a large amount of dimers that become too much to be able to repair

Question 17

What are the basic differences between how ionizing vs. non-ionizing radiation work to control microbial growth? (give examples of each type of radiation)

Non-Ionizing:

Answer 17

Non Ionizing radiation: excites atoms but does not ionize them; does cause breaks in mutations but does not cause breaks in DNA
Example: UV rays
Not as penetrating; poor penetration through glass, metal, cloth
Causes pyrimidine dimers - mutations
Destroys most fungal cells, bacterial vegetative cells, protozoa, and viruses but not all
Possibly kills endospores with longer periods of exposure
Uv radiation usually disinfects, not sterilizes
Used in hospital rooms, labs, food prep areas, dental offices
Used to treat drinking water or purify liquids

Question 18

Explain the basics of how each of the following work to control microbial growth: alcohol

Answer 18

Alcohol: dissolves outer membrane of gram negative; dissolves cell membranes if in higher amounts and longer exposure
Best microbial activity at 70%

Question 19

Explain the basics of how each of the following work to control microbial growth: acids/bases

Answer 19

Acids and bases: very low or high pH can destroy or inhibit microbial cells
Acetic acid
Lactic acid
Boric acid
Used for vaginal bacterial infections

Question 20

Explain the basics of how each of the following work to control microbial growth: phenols

Answer 20

Phenols: cytoplasmic and membrane target
Triclosan is found in disinfectant and antiseptic, cat litter, and soaps
Ban on triclosan in minnesota; phenol leads to bacterial resistance or homoronal effects
Phenols shape being similar to hormone shape causes hormonal effects

Question 21

Explain the basics of how each of the following work to control microbial growth: heavy metals

Answer 21

Heavy Metals: Some soaps, Hg, Ag, Au, Cu, As, and Zn have been used - they inactivate proteins, can coat surfaces to make sterile, can be applied in small amounts to burns to minimize infection
Any metal will inactivate proteins = it dies

Question 22

Explain the basics of how each of the following work to control microbial growth: hydrogen peroxide

Answer 22

Hydrogen peroxides: produce free radicals which are toxic and damaging to cells
Can be harmful to tissues
Bactericidal, virucidal, and fungicidal
In higher concentration will kill endospores

Question 23

How do halogens play a role in microbial control?

Answer 23

Halogens: interfere with or damage proteins
Ex: Fluorine, Bromine, Chlorine, and Iodine
Can be used to purify water