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Z BIO103 - MICROBIOLOGY (LECTURE) > Control for microbial growth & preservation > Flashcards

Control for microbial growth & preservation Flashcards

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1
Q

Control of Microbial Growth

A
  • safety
  • preservation
  • manipulation
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2
Q

Terminology Relating to the Control of Microbial Growth

A
  • Sterilization
  • Comercial Sterilization
  • Disinfection
  • Antisepsis
  • Degerming
  • Sanitization
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3
Q

Definition of Sterilization

A

Destruction or removal of all forms of microbial life, including endospores but with the possible exception of prions

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4
Q

Sterilization is usually done by _____ ____ ______ or a _______ ____, such as ____ ____

A
  • steam under pressure
  • sterilizing gas
  • ethylene oxide
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5
Q

Definition of Comercial Sterilization

A

Sufficient heat treatment to kill endospores of Clostridium botulinum in canned food

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6
Q

In commercial sterilization, more-resistant endospores of ________ _____ may ______, but they will not ______ and _____ under normal storage conditions

A
  • thermophilic bacteria
  • survive
  • germinate and grow
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7
Q

Definition of Disinfection

A

Destruction of vegetative pathogens on inanimate objects

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8
Q

Disinfection can make use of ______ or ______ methods

A

physical or chemical

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9
Q

Definition of Antisepsis

A

Destruction of vegetative pathogens on living tissue

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10
Q

In Antisepsis, treatment is almost always by ______ _________

A

chemical antimicrobials

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11
Q

Definition of Degerming

A

Removal of microbes from a limited area, such as the skin around an injection site

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12
Q

Degerming is mostly a ______ ______ by ____ and _____ or an _____________

A
  • mechanical removal
  • soap and water
  • alcohol-soaked swab
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13
Q

Definition of Sanitization

A

Treatment is intended to lower microbial counts on eating and drinking utensils to safe public health levels

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14
Q

Sanitization may be done with _______ ______ or by _____ into a
______ _______

A
  • high-temperature washing
  • dipping into a chemical disinfectant
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15
Q

What are the factors that affect the control of microbial growth?

A
  • Temperature
  • pH
  • Gas
  • Moisture
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16
Q

High Temperature

A
  • boiling
  • moist-heat sterilization
  • hot-air sterilization
  • microwave
  • pasteurization
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17
Q

pH

A
  • salt
  • sugar
  • acid
  • base
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18
Q

Gas

A
  • vacuum
  • infused CO2
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19
Q

Moisture

A
  • add solute
  • allow heat to dehydrate
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20
Q

It is the lowest temperature at which all the microorganisms in a particular liquid suspension will be killed in 10 minutes

A

Thermal death point (TDP)

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21
Q

It is the minimal length of time for all bacteria in a particular liquid culture to be killed at a given temperature

A

Thermal death time (TDT)

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22
Q
  • D value
  • a third concept related to bacterial heat resistance
  • is the time, in minutes, in which 90% of a population of bacteria at a given temperature will be killed
A

Decimal reduction time (DRT)

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23
Q

It kills microorganisms primarily by coagulating proteins (denaturation)

A

Moist-heat Sterilization

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24
Q

This coagulation of proteins or denaturation is caused by

A

breakage of the hydrogen bonds that hold the proteins in their three-dimensional structure

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25
Q

One type of mois-heat sterilization

A

Boiling

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26
Q

It kills vegetative forms of bacterial pathogens, many viruses and fungi and their spores within about 10 minutes, usually much faster

A

Boiling

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27
Q

Realiable moist heat sterilization

A

Autoclaving at 121°C for 5-20min with 15 psi of pressure

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28
Q

What are the equipments that are sterilize by autoclaving and can withstand high temperature and pressure?

A
  • culture media
  • instruments
  • dressings
  • intravenous equipment
  • applicators
  • solutions
  • syringes
  • transfusion equipment
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29
Q

A method discovered by Loius Pasteur of preventing the spoilage of beer and wine

A

Pateurization

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30
Q

A test that is used by dairy industry to determine whether products have been pasteurized

A

Phosphatase test

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31
Q

an enzyme naturally present in
milk

A

Phosphatase

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32
Q

Intent in Pasteurization in milk

A

to eliminate pathogenic microbes

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33
Q

Pasteurization in milk that uses of at least 72°C, but for only 15 seconds

A

High-temperature short-time (HTST) pasteurization

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34
Q

HTST pasteurization ____ ____ ______ ____, so the milk keeps well under refrigeration

A

lowers total bacterial counts

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35
Q

Milk can also be sterilized by

A

Ultra-high-temperature (UHT) treatments

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36
Q

as the temperature is increased, much less time is needed to kill the same number of microbes

A

Equivalent treatment

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37
Q

kills microorganisms by oxidation effects

A

Dry Heat Sterilization

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38
Q

One of the simplest methods of dry heat sterilization

A

Direct Flaming

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39
Q

Direct Flaming

A

Burning contaminants to ashes

40
Q

an effective way to sterilize and dispose of contaminated paper cups, bags, and dressings

A

Incineration

41
Q

Incineration

A

Burning to ashes

42
Q

Another form of dry heat sterilization

A

Hot-air sterilization

43
Q

Hot-air sterilization

A

Oxidation

44
Q

Items to be sterilized by this procedure are placed in an
_____

A

oven

45
Q

Temperature needed in Hot-air sterilization

A

170°C

46
Q

What is required in Hot-air Sterilization?

A

long period and higher temperature

47
Q

Why does the longer period and higher temperature are required n Hot-air Sterilization?

A

because the heat in water is more readily transferred to a cool body than is the heat in air

48
Q

It is the passage of a liquid or gas through a screenlike material with pores small enough to retain microorganisms

A

Filtration

49
Q

Filtration

A

Separation of bacteria from
suspending liquid

50
Q

Filtration is used to __

A

sterilize heat-sensitive materials

51
Q

What are the example of heat-sensitive materials

A
  • some culture media
  • enzymes
  • vaccines
  • antibiotic solutions
52
Q

It remove almost all microorganisms larger than about 0.3 mm in diameter

A

High-efficiency particulate air (HEPA) filters

53
Q

Unseen pathogens that passed through the filters (causing such diseases as rabies) were called _____ ____

A

filterable viruses

54
Q

What is the filter used in early days of microbiology used to filter liquids?

A

hollow candle-shaped
filters of unglazed porcelain

55
Q

Filter that is composed of such substances as cellulose esters or plastic polymers, popular for industrial and laboratory use

A

Membrane Filters

56
Q

Thickness of the filters of the membrane filter

A

only 0.1 mm thick

57
Q

Flexible and wall-less bacteria

A
  • spirochetes
  • mycoplasma
58
Q

a size that will retain viruses and even some large protein molecules

A

pores as small as 0.01 mm

59
Q

Low Temperature

A

Refrigeration

60
Q

Refrigeration

A

Decreased chemical reactions and possible changes in proteins

61
Q

Temperature of ordinary refrigerators

A

0–7°C

62
Q

Metabolic rate of microbes in refrigerators

A

metabolic rate of most microbes is so reduced that they cannot reproduce or synthesize toxins

63
Q

Ordinary refrigeration has a _______ effect

A

bacteriostatic

64
Q

Yet __________ do grow slowly at refrigerator temperatures and will alter the _________ and ______ of foods over time

A
  • psychrotrophs
  • appearance and taste
65
Q

A bacteria that can grow at refrigrator temperatures

A

Listeria

66
Q
  • it is more harmful to bacteria
  • the ice crystals that form and grow disrupt the cellular and molecular structure of the bacteria
A

Slow freezing

67
Q
  • being inherently slower
  • is actually the more damaging part of a freeze-thaw cycle
A

Thawing

68
Q
  • an eukaryotic parasites that cause human trichinellosis
  • are killed by several days of freezing temperatures
A

Roundworms

69
Q
  • it alters the molecular structures of proteins and carbohydrates, resulting in the rapid inactivation of vegetative bacterial cells
  • preserve the flavors, colors, and nutrient values of the products
A

High Pressure

70
Q

Absence of water

A

Desiccation

71
Q

Microorganisms cannot _____ or ______ but can remain _____ for year

A
  • grow or reproduce
  • viable
72
Q
  • freeze-drying
  • a laboratory process for preserving microbes
A

Lyophilization

73
Q

The use of high concentrations of salts and sugars to preserve food

A

Osmotic pressure

74
Q

Two types of radiation that kills microorganisms (sterilizing radiation)

A

Ionizing and Nonionizing

75
Q
  • gamma rays, X rays, and high-energy electron beams
  • has a shorter wavelength, less than about 1 nm
  • carries much more energy
A

Ionizing radiation

76
Q

Ionizing radation

A

Destruction of DNA

77
Q

are emitted by certain radioactive elements such as cobalt

A

Gamma rays

78
Q

are produced by machines in a manner similar to the production of electron beams

A

X rays

79
Q

have much lower penetrating power but usually require only a few seconds of exposure

A

High-energy electron beams

80
Q

The principal effect of ionizing radiation

A

the ionization of water which forms highly reactive hydroxyl radicals

81
Q

Low-level ionizing radiation is used for

A

processing spices and certain meats and vegetables

82
Q

It is used to sterilize pharmaceuticals and disposable dental and medical supplies, such as plastic syringes, surgical gloves, suturing materials, and catheters

A

Ionizing radiation:
High-energy electron beams

83
Q

As a protection against ________, the postal service often uses electron beam radiation to sterilize certain classes of ____

A
  • bioterrorism
  • mail
84
Q
  • has a longer wavelength
  • usually greater than about 1 nm
A

Nonionizing radiation

85
Q

Nonionizing radiation

A

Damage to DNA

86
Q

Best example of nonionizing radiation

A

Ultraviolet (UV) light

87
Q

It inhibit correct replication of the DNA during cell reproduction

A

Thymine dimers

88
Q

The UV wavelengths most effective for killing microorganisms are about

A

260 nm

89
Q

A UV, or ________ lamp is commonly found in hospital rooms, nurseries, operating rooms, and cafeterias

A

germicidal

90
Q

UV light is also used to disinfect _______ and other ______ _______

A
  • vaccines
  • medical products
91
Q

Disadvantage of UV light as a disindectant

A

the radiation is not very penetrating

92
Q

Potential problem of UV light

A
  • can damage human eyes
  • prolonged exposure can cause burns and skin cancer in humans
93
Q

It does not have much direct effect on microorganisms

A

Microwave

94
Q

Preservation

A
  • short term
  • long term
95
Q

Short term

A
  • replace sterile rubber cup (aseptically)
  • put sterile mineral oil/glycerol (6 months to 1 year)
96
Q

Long term

A
  • liquid nitrogen
  • lyophilization

Z BIO103 - MICROBIOLOGY (LECTURE) (7 decks)

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