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Microbiology > Control of Microbial Growth II > Flashcards

Control of Microbial Growth II Flashcards

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Biology 101 flashcards
1
Q

What are the 5 categories of physical methods of control

A

Moist heat, dry heat, filtration, radiation, and high pressure

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2
Q

What is the only method that is not bactericidal

A

Filtration

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3
Q

What are the three methods of moist heat

A

Boiling
Pasteurization
Autoclaving

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4
Q

What are the two methods of dry heat

A

incineration

dry heat ovens

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5
Q

what are the two ways to filtrate

A

filtration of fluids, filtration of air

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6
Q

What are the two methods of radiation

A

Ionizing radiation and UV radiation

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7
Q

Moist heat can be used to….

A

sterilize or disinfect

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8
Q

Describe the method of boiling

A
  • destroys most microorganisms and viruses
  • achieves disinfection
  • bactericidal
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9
Q

Describe the method of pasteurization

A

destroys only pathogens and spoilage organisms

  • bacteriostatic (reduction in the # of microbes)
  • bactericidal since it kills the pathogens
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10
Q

What does the term bacteriostatic mean

A

reduction in the number of microbes

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11
Q

What does the term bactericidal mean

A

kills the microbes (does not necessarily reach sterilization)

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12
Q

Describe the method of autoclaving

A
  • achieves sterilization using pressurized steam
  • Occurs at 121 degrees C, 15 psi in 15 minutes
  • bactericidal method
  • can destroy prions if settings are changed
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13
Q

What is the purpose of commercial canning processes

A

designed to destroy Clostridium botulinum endospores

-canned food is commercially sterile (removal of only these endospores)

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14
Q

Which is more effective, moist heat of dry heat

A

moist heat;

dry heat does not penetrate well and takes longer times and higher temperatures (200 degrees celsius for 90 minutes)

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15
Q

describe the method of hot air ovens

A

oxidize cell components and denature proteins

  • bactericidal
  • can achieve sterilization
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16
Q

describe the method of incineration

A
  • achieves sterilization
  • oxidizes cell to ashes
  • used to destroy medical waste and animal carcasses
  • can destroy prions very effectively
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17
Q

T/F you can sterilize your inoculating loop by flaming it

A

True

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18
Q

When is filtration option used

A

when materials cannot withstand heat treatment

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19
Q

what type of filter would be used for fluids

A

membrane filter, they contain small pores that even the smallest virus can not fit through, thus physically separating microbes from the sample

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20
Q

What type of filter is used for the filtration of air

A

HEPA: high efficiency particulate air, removes nearly all microbes from air

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21
Q

T/F filtration is considered both bactericidal and bacteriostatic

A

False, it is neither since the microbes are only separated, they are not inhibited in growth or killed

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22
Q

T/F Filtration does not achieve sterilization

A

False

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23
Q

When is a radiation method used

A

typically with solid objects, generally after packing

-FDA has approved its use in fruits, veggies, pork, poultry, etc..

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24
Q

What are two forms of ionization radiation? what level of control do they achieve?

A

Gamma rays and X rays

both achieve sterilization

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25
Q

How does Ultraviolet radiation work as a control method? what level of control does it achieve?

A
  • destroys microbes directly in air, water or on surfaces

- will only disinfect since they cannot penetrate endospores

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26
Q

Is UV radiation ionizing or non-ionizing

A

non-ionizing

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27
Q

What is the drawback on using UV radiation

A

It has poor penetrating power, it cannot kill microbes in solids or turbid liquids

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28
Q

Describe microwaves as a method of control

A
  • kill by generate heat, not directly

- heats food unevenly so cells can survive

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29
Q

Drawbacks of microwaves as a method of control

A

-operates in a bactericidal method but does not effectively achieve disinfection evenly so not a good control method

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30
Q

Describe the method of high pressure as a control method

A
  • used in pasteurization of commercial foods (ex. guac)
  • avoids problems with high temperature pasteurization
  • products maintain color, flavor associated with fresh food
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31
Q

What level of control does high pressure reach

A
  • Not sterilization, but extension of shelf life
  • disinfection
  • bactericidal but does not kill endospores
32
Q

What are the 10 examples of chemical control methods

A
  1. Alcohols
  2. Aldehydes
  3. Biguanides
  4. Ethylene Oxide gas
  5. Halogens
  6. Metals
  7. Ozone
  8. Peroxygens
  9. Phenolic Compounds
  10. Quaternary Ammonium compounds
33
Q

Describe the use of alcohol as a control method

A
  • aqueous solution of ethyl or isopropyl alcohol
  • kills vegetative bacteria and fungi
  • not reliable against endospores and some naked viruses
34
Q

What is alcohol commonly used as in terms of chemical control

A

an antiseptic or disinfectant

35
Q

What are the limitations for using alcohol as a control method

A
  • evaporates quickly, limiting contact time

- much use aqueous solution

36
Q

What is the importance of using an aqueous alcohol solution? What is the proper range of dilution?

A

100% will not work bc it will denature proteins and effect the lipid membrane
-also needs water for the chemical reaction to occur (70% alcohol is most commonly used) but the range could be anywhere from 60-98%

37
Q

What is the role of aldehydes as a chemical control method

A
  • used as a commercial sterilant

- bactericidal with sterilizing effects

38
Q

What are examples of aldehydes used in chemical control methods and what is an example of their use

A

Glutaraldehyde- -immersion in 2% alkaline glutaraldehyde will kill all microbial life in 10-12 hours
formaldehyde- used as a gas or as formalin (37% solution) used commonly in hospital settings

39
Q

What is the drawback of using formaldehyde as a method of aldehyde chemical control?

A

can be toxic if used over a long period of time with high concentration

40
Q

What is the role of biguanides as a chemical control method?

A
  • Bactericidal with antiseptic effects
  • stays on skin and mucous membranes
  • common in skin cream, mouth wash, soaps and lotions
41
Q

What is the most effective biguanides

A

chlorhexidine- adheres very tightly to the mucous membrane, remains there for a particular period of time

42
Q

what is the role of ehtylene oxide gas as a chemical control method?

A
  • very powerful sterilant
  • Used generally for sterilization of disposable lab items, equipment, implantable devices such as pacemakers and artificial hips
  • major use in the medical industry
43
Q

What are the role of metal compounds as a chemical control method?

A
  • Used as a disinfectant
  • High concentrations may be too toxic to use medically
  • Silver still used in creams and bandages as well as silver nitrate drops for infants
44
Q

T/F Mercury, tin, and copper were once widely used as preservatives

A

True, but mercury is not longer used because of its toxicity levels

45
Q

What are two types of Halogens used for chemical control methods

A
  1. Chlorine

2. Iodine

46
Q

Role of Chlorine as a halogen control method

A
  • used as a disinfectant
  • bactericidal
  • casustic to skin and mucous membranes
  • used in household bleach
47
Q

Drawback to using chlorine

A

it is not very effective with the presence of organic compounds

48
Q

Role of Iodine as a halogen control method

A
  • mild enough to be used as an antiseptic/disinfectant

- bactericidal

49
Q

Drawback of using iodine

A

unreliable on endospores and difficult to treat organic compounds with

50
Q

Iodine is commonly used as what

A

an Iodophore, which slowly releases iodine from a carrier molecule

51
Q

What are two examples of peroxygens

A
  1. Hydrogen peroxide

2. Peracetic Acid

52
Q

Why are peroxygens good in control and what level of control do they achieve

A

they are powerful oxidizers, can be used as a disinfectant or antiseptic

53
Q

What does the effectiveness of Hydrogen peroxide depend on

A

The surface being treated

54
Q

T/F hydrogen peroxide is more effective as an antiseptic

A

False, because aerobic bacteria produce the enzyme catalase which breaks it down to water and oxygen and both human cells and microbes have the ability to break down hydrogen peroxide

55
Q

What kind of wounds is hydrogen peroxide more effective in disinfecting

A

deeper wounds because Hydrogen peroxide broken down will produce oxygen which will prevent the establishment of anaerobic microbes

56
Q

Hydrogen peroxide is more effective as either a disinfectant or an antiseptic

A

better as a disinfectant

57
Q

What phase of hydrogen peroxide can be used as a sterilant

A

the vapor-phase

58
Q

Which is more potent, peracetic acid of Hydrogen peroxide?

A

Peracetic acid

59
Q

What is the advantage of using peracetic acid as a peroxygen

A
  • effective on organic material

- useful on a wide range of material

60
Q

T/F Phenolics were one of the earliest used disinfectants

A

True, used by Joseph Lister

61
Q

What is the level of control achieved by a phenolic compound

A

can be used as a disinfectant or an antiseptic

62
Q

What is the advantage of using a phenolic compound

A
  • wide activity range, reasonable cost and will remain effective in presence of detergents and organic matter
  • some sufficiently non-toxic, used in soaps and lotions
63
Q

T/F you can use phenols directly on your skin

A

False, need to be a modified form, used as a phenolic because a phenol will burn your skin
Ex: Triclosan used in soap and lotion

64
Q

What is the role of Quaternary Ammonium compounds as a chemical control method?

A
  • It is a positively (cationic) charged detergent

- Nontoxic used to disinfect food preparation surfaces

65
Q

What are two methods of Preservation of Perishable products

A
  1. Chemical preservatives

2. Low Temperature storage

66
Q

T/F all methods of preservation or perishable products are bacteriostatic

A

True, that stop the growth but will still have the microbes present

67
Q

What are two different types of chemical preservatives?

A
  1. Weak organic acids

2. Nitrate and nitrite used in processed meats

68
Q

What is the role of weak organic acids as chemical preservatives and what are some examples

A

-benzoic, sorbic, propionic acids

Control molds and bacteria in foods and cosmetics

69
Q

What is the role of nitrate and nitrite as chemical preservatives

A
  1. Inhibit endospore germination and vegetative cell growth

2. Higher concentrations give meats pink color

70
Q

What is the importance of refrigeration for low-temperature storage of perishable products

A

it inhibits (without killing) growth of pathogens and spoilage organisms by slowing or stopping enzyme reactions

71
Q

T/F psychrotrophs, psychrophillic organisms can still grow in refrigeration

A

True

72
Q

T/F Freezing preserves by slowing all microbial growth

A

False, it preserves by STOPPING all microbial growth

73
Q

What are three ways you can reduce available water to preserve perishable products

A
  1. Accomplished by salting, adding sugar
  2. Lyophilization
  3. Drying

** All are bacteriostatic methods

74
Q

What is the role of adding salt and sugar to preserve perishable products

A
  • increases environmental solutes

- causes cellular plasmolysis where water exits the bacterial cells

75
Q

What is the role of lyophilization in order to preserve perishable products

A
  • freeze-drying
  • also dehydrates, stopping the growth of microbes
  • application of low temperature and drying
  • ex: in coffee, milk, meats, fruits, veggies
76
Q

What is the role of drying in preservation of perishable products

A
  • stops microbial growth but does not reliably kill

- drying=dehydration

Microbiology (7 decks)

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