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Microbiology 101 > Exam II: Controlling Microbial Growth > Flashcards

Exam II: Controlling Microbial Growth Flashcards

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1
Q

Bacterial growth means…

A

Increase in number of cells, not the size!

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2
Q

Bacterial growth depends on… (5 things)

A

Temperature, pH, osmotic pressure, oxygen, nutrients

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3
Q

Log phase cultures are most sensitive to…?

A

Growth inhibition

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4
Q

Define “generation time”

A

The time required for the cell to divide/population to double

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5
Q

Average bacteria generation time

A

1-3 hours

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6
Q

E. coli generation time

A

20 minutes

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7
Q

Define: Antisepsis

A

Reduction of # of microorganisms and viruses on LIVING tissue

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8
Q

Define: Aseptic

A

An environment or procedure free of pathogenic contaminants

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9
Q

Define: -cide / -cidal

A

Indicates kills/destruction of a type of microbe

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10
Q

Define: Degerming

A

Removal of microbes by mechanical means

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11
Q

Define: Disinfection

A

Destruction of most microorganisms and viruses on NON-LIVING tissue

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12
Q

Define: Pasteurization

A

Use of heat to destroy pathogens and reduce spoilage microorganisms in foods and beverages

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13
Q

Define: Sanitization

A

Removal of ENOUGH pathogens from objects to meet public health standards

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14
Q

Define: -stasis / -static

A

Indicates INHIBITION. Prevents growth of microbe (not a complete destruction)

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15
Q

Define: Sterilization

A

Destruction of ALL microorganisms and viruses in or on an object.

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16
Q

What factors affect how long it takes to kill bacteria? (4 things)

A

Number of microbes, Environment, Time of exposure, Characteristics of microbes

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17
Q

What environmental conditions slow the time to kill microbes?

A

Organic materials, Biofilm (such as feces, sewage, etc)

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18
Q

What environmental conditions speed up the time to kill microbes?

A

Prior cleaning, Heat

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19
Q

What microbe characteristics are most resistant to kill? (3 things)

A

Spores, Thick lipid coats, Protozoan cysts

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20
Q

What are the 3 actions of microbial control agents?

A

Alteration of membrane permeability, Damage to proteins and nucleic acids prevents functions of proteins and enzymes, Mutation/messing up the DNA to make non functional proteins

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21
Q

Define: Thermal Death Time

A

How long it takes to kill a certain bacteria at a certain temperature

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22
Q

What is the time/temp for pasteurization, and what does it do?

A

63’C for 30 minutes. Lowers # of pathogens in food products that would be damaged by longer heating times

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23
Q

What is the time/temp for UHT sterilization, and what is a potential side effect of using this method?

A

140’C 1-3 seconds. It may cause the loss of nutritional value of the food product.

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24
Q

How does moist heat work to control microbes?

A

It coagulates proteins by denaturing (breaking hydrogen bonds).

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25
Q

How long do most pathogens need to boil to kill microbes?

A

10 minutes

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26
Q

How long does something need to boil to kill Hepatitis virus?

A

30 minutes

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27
Q

How long does it take for boiling to kill spores?

A

20 hours

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28
Q

How does an autoclave work?

A

Heat + pressure

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29
Q

What are the specifications for using an autoclave?

A

15 psi for 15 minutes at 121 ‘C

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30
Q

What temp/time is used for dry heat in an oven? When would you use dry heat?

A

170’C for 2 hours. When things cannot go into the autoclave, or would be damaged by steam/moisture

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31
Q

What is resistant to dry heat?

A

Spores

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32
Q

Low temperature: Refrigeration is….

A

Bacteriostatic

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33
Q

What microbe is psycrotolerant, and can grow in a refrigerator?

A

Listeria

34
Q

What is the problem with ice crystals that are formed when freezing something?

A

The crystals mechanically shear the plasma membrane

35
Q

How is freezing used for preservation, in some cases? (What is used?)

A

Dry ice and 95% ethanol

36
Q

Dessication is …

A

Bacteriostatic

37
Q

What is the term and an example of when drying out is used for preservation?

A

Lyophilization (eg freeze drying)

38
Q

What is most resistant to water limiting methods of killing or preserving?

A

Molds and yeasts

39
Q

What type of radiation would you use on spices, vegetables, and certain meats?

A

Low Level Ionizing Radiation

40
Q

What type of radiation would you use on medical supplies?

A

High Energy Electron Beams

41
Q

How does radiation work?

A

It causes mutations and death of cells

42
Q

What is affected in UV radiation to cause gene mutations?

A

Thymine dimers in DNA

43
Q

How would you use UV radiation? When would you use it?

A

Germicidal lamps, Vaccine disinfection. Might use it to kill organisms when something is sensitive to moisture, heat, etc.

44
Q

What kind of effect does a microwave have on microbes?

A

Very little

45
Q

What is the problem with microwaves?

A

It works by activating water molecules, so solid foods are heated unevenly

46
Q

Phenols are a type of…

A

Disinfectant/Antiseptic

47
Q

Disinfectants/Antiseptics are chemicals with what kind of effect?

A

antigermicidal

48
Q

How do Phenols work?

A

Damage lipid membranes

49
Q

Where are phenols active?

A

In presence of organic matter

50
Q

Which type of disinfectants/antiseptics are broad spectrum?

A

Bisphenols

51
Q

What type of substance are hexachlorophine and triclosan? Where are they commonly used?

A

Bisphenols. Used in antibacterial soaps and toothpastes.

52
Q

Chlorhexidine is what type of disinfectant/antiseptic?

A

Biguanide

53
Q

What is a benefit of chlorhexidine, and where might it be used?

A

Low toxicity, can be used on skin and mucous membranes. Used as surgical scrub in veterinary hospitals.

54
Q

Iodine and Chlorine are example of what kind of substance?

A

Halogens

55
Q

How does chlorine work? What warnings should be considered?

A

Destroys cell walls and enzymes. It is nondiscriminatory, therefore not good on human tissues.

56
Q

What is the name of chlorine gas, and how is it adapted for use for disinfection?

A

Hypochlorite. It is dissolved into water to form bleach.

57
Q

How does alcohol (disinfectant/antiseptic) work?

A

Protein denaturation and membrane damage

58
Q

What aspect of alcohol use is both good and bad? Why is it bad?

A

Evaporates quickly. Bad because it takes 90 seconds to kill organisms

59
Q

What are 2 examples of alcohols?

A

Ethanol, isopropanol

60
Q

Why is 100% alcohol not good?

A

The water component is needed to denature proteins.

61
Q

How do heavy metals work as a disinfectant?

A

Denatures proteins

62
Q

What is an example of a heavy metal used as a topical cream?

A

Silver nitrate

63
Q

What poisonous heavy metal disinfectant was used to treat syphilis and is painted on?

A

Mercuric chloride

64
Q

What is the copper sulfite heavy metal disinfectant used for?

A

Algaecide

65
Q

Where might you find zinc as a heavy metal disinfectant?

A

Mouthwash, paints

66
Q

How do surfactants work?

A

Decrease surface tension and damage lipid membranes. They essentially poke holes in membrane! They are often used in conjunction with something else (but not always)

67
Q

What disinfectant/surfactant combination is often used for mold abatement?

A

10% bleach (disinfectant) + Ivory soap (surfactant)

68
Q

Sodium benzoate is a chemical food preservative that is used in what kind of foods? It works by doing what to the pH, which in turn affects what enzyme in what way?

A

Used in acidic foods. It REDUCES pH, which INACTIVATES PHOSPHOFRUCTOKINASE.

69
Q

Sorbic acid is a chemical food preservative that works in what way?

A

Inhibits enzymes

70
Q

Calcium proponate is a non-toxic chemical food preservative that is used on what type of food? How does it work?

A

Bread. Inhibits growth.

71
Q

Sodium nitrate and sodium nitrite are toxic chemical food preservatives that work in what way, and on what microbe?

A

Inhibits Clostridium botulinum.

72
Q

Formaldehyde and glutaraldehyde are examples of what, and what action do they take?

A

Aldehydes. Preserving

73
Q

How do aldehydes work?

A

Irreversibly cross-link protein molecules (they will not work anymore)

74
Q

What are 2 examples of when aldehydes may be used?

A

Instrument disinfection, Tissue preservation for pathology

75
Q

What is ethylene oxide used for and how does it work?

A

Gas sterilization. It denatures proteins.

76
Q

What is a benefit of gas sterilization, and when would you use it?

A

High penetration! It kills all spores and microbes with lengthy exposure. Use it when something would otherwise be sensitive to heat or moisture.

77
Q

Ozone, hydrogen peroxide, benzoyl peroxide, and paracetic acid are examples of what?

A

Oxidizing agents

78
Q

What is a downside to hydrogen peroxide?

A

It is very toxic

79
Q

What is paracetic acid especially good for, and how does it work?

A

Anaerobes. Interferes with metabolism

80
Q

In practical terms, what does the term “sterilization” refer to?

A

The elimination of all harmful microorganisms and viruses (although some microbes may still be present)

81
Q

Which substance/process would one use to kill microbes on laboratory surfaces?

A

Disinfectants

Microbiology 101 (10 decks)

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