Control for microbial growth & preservation Flashcards
1
Q
Control of Microbial Growth
A
- safety
- preservation
- manipulation
2
Q
Terminology Relating to the Control of Microbial Growth
A
- Sterilization
- Comercial Sterilization
- Disinfection
- Antisepsis
- Degerming
- Sanitization
3
Q
Definition of Sterilization
A
Destruction or removal of all forms of microbial life, including endospores but with the possible exception of prions
4
Q
Sterilization is usually done by _____ ____ ______ or a _______ ____, such as ____ ____
A
- steam under pressure
- sterilizing gas
- ethylene oxide
5
Q
Definition of Comercial Sterilization
A
Sufficient heat treatment to kill endospores of Clostridium botulinum in canned food
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
7
Q
Definition of Disinfection
A
Destruction of vegetative pathogens on inanimate objects
8
Q
Disinfection can make use of ______ or ______ methods
A
physical or chemical
9
Q
Definition of Antisepsis
A
Destruction of vegetative pathogens on living tissue
10
Q
In Antisepsis, treatment is almost always by ______ _________
A
chemical antimicrobials
11
Q
Definition of Degerming
A
Removal of microbes from a limited area, such as the skin around an injection site
12
Q
Degerming is mostly a ______ ______ by ____ and _____ or an _____________
A
- mechanical removal
- soap and water
- alcohol-soaked swab
13
Q
Definition of Sanitization
A
Treatment is intended to lower microbial counts on eating and drinking utensils to safe public health levels
14
Q
Sanitization may be done with _______ ______ or by _____ into a
______ _______
A
- high-temperature washing
- dipping into a chemical disinfectant
15
Q
What are the factors that affect the control of microbial growth?
A
- Temperature
- pH
- Gas
- Moisture
16
Q
High Temperature
A
- boiling
- moist-heat sterilization
- hot-air sterilization
- microwave
- pasteurization
17
Q
pH
A
- salt
- sugar
- acid
- base
18
Q
Gas
A
- vacuum
- infused CO2
19
Q
Moisture
A
- add solute
- allow heat to dehydrate
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)
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)
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)
23
Q
It kills microorganisms primarily by coagulating proteins (denaturation)
A
Moist-heat Sterilization
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
25
One type of mois-heat sterilization
Boiling
26
It kills vegetative forms of bacterial pathogens, many viruses and fungi and their spores within about 10 minutes, usually much faster
Boiling
27
Realiable moist heat sterilization
Autoclaving at 121°C for 5-20min with 15 psi of pressure
28
What are the equipments that are sterilize by autoclaving and can withstand high temperature and pressure?
- culture media
- instruments
- dressings
- intravenous equipment
- applicators
- solutions
- syringes
- transfusion equipment
29
A method discovered by Loius Pasteur of preventing the spoilage of beer and wine
Pateurization
30
A test that is used by dairy industry to determine whether products have been pasteurized
Phosphatase test
31
an enzyme naturally present in
milk
Phosphatase
32
Intent in Pasteurization in milk
to eliminate pathogenic microbes
33
Pasteurization in milk that uses of at least 72°C, but for only 15 seconds
High-temperature short-time (HTST) pasteurization
34
HTST pasteurization ____ ____ ______ ____, so the milk keeps well under refrigeration
lowers total bacterial counts
35
Milk can also be sterilized by
Ultra-high-temperature (UHT) treatments
36
as the temperature is increased, much less time is needed to kill the same number of microbes
Equivalent treatment
37
kills microorganisms by oxidation effects
Dry Heat Sterilization
38
One of the simplest methods of dry heat sterilization
Direct Flaming
39
Direct Flaming
Burning contaminants to ashes
40
an effective way to sterilize and dispose of contaminated paper cups, bags, and dressings
Incineration
41
Incineration
Burning to ashes
42
Another form of dry heat sterilization
Hot-air sterilization
43
Hot-air sterilization
Oxidation
44
Items to be sterilized by this procedure are placed in an
_____
oven
45
Temperature needed in Hot-air sterilization
170°C
46
What is required in Hot-air Sterilization?
long period and higher temperature
47
Why does the longer period and higher temperature are required n Hot-air Sterilization?
because the heat in water is more readily transferred to a cool body than is the heat in air
48
It is the passage of a liquid or gas through a screenlike material with pores small enough to retain microorganisms
Filtration
49
Filtration
Separation of bacteria from
suspending liquid
50
Filtration is used to __
sterilize heat-sensitive materials
51
What are the example of heat-sensitive materials
- some culture media
- enzymes
- vaccines
- antibiotic solutions
52
It remove almost all microorganisms larger than about 0.3 mm in diameter
High-efficiency particulate air (HEPA) filters
53
Unseen pathogens that passed through the filters (causing such diseases as rabies) were called _____ ____
filterable viruses
54
What is the filter used in early days of microbiology used to filter liquids?
hollow candle-shaped
filters of unglazed porcelain
55
Filter that is composed of such substances as cellulose esters or plastic polymers, popular for industrial and laboratory use
Membrane Filters
56
Thickness of the filters of the membrane filter
only 0.1 mm thick
57
Flexible and wall-less bacteria
- spirochetes
- mycoplasma
58
a size that will retain viruses and even some large protein molecules
pores as small as 0.01 mm
59
Low Temperature
Refrigeration
60
Refrigeration
Decreased chemical reactions and possible changes in proteins
61
Temperature of ordinary refrigerators
0–7°C
62
Metabolic rate of microbes in refrigerators
metabolic rate of most microbes is so reduced that they cannot reproduce or synthesize toxins
63
Ordinary refrigeration has a _______ effect
bacteriostatic
64
Yet __________ do grow slowly at refrigerator temperatures and will alter the _________ and ______ of foods over time
- psychrotrophs
- appearance and taste
65
A bacteria that can grow at refrigrator temperatures
Listeria
66
- it is more harmful to bacteria
- the ice crystals that form and grow disrupt the cellular and molecular structure of the bacteria
Slow freezing
67
- being inherently slower
- is actually the more damaging part of a freeze-thaw cycle
Thawing
68
- an eukaryotic parasites that cause human trichinellosis
- are killed by several days of freezing temperatures
Roundworms
69
- 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
High Pressure
70
Absence of water
Desiccation
71
Microorganisms cannot _____ or ______ but can remain _____ for year
- grow or reproduce
- viable
72
- freeze-drying
- a laboratory process for preserving microbes
Lyophilization
73
The use of high concentrations of salts and sugars to preserve food
Osmotic pressure
74
Two types of radiation that kills microorganisms (sterilizing radiation)
Ionizing and Nonionizing
75
- gamma rays, X rays, and high-energy electron beams
- has a shorter wavelength, less than about 1 nm
- carries much more energy
Ionizing radiation
76
Ionizing radation
Destruction of DNA
77
are emitted by certain radioactive elements such as cobalt
Gamma rays
78
are produced by machines in a manner similar to the production of electron beams
X rays
79
have much lower penetrating power but usually require only a few seconds of exposure
High-energy electron beams
80
The principal effect of ionizing radiation
the ionization of water which forms highly reactive hydroxyl radicals
81
Low-level ionizing radiation is used for
processing spices and certain meats and vegetables
82
It is used to sterilize pharmaceuticals and disposable dental and medical supplies, such as plastic syringes, surgical gloves, suturing materials, and catheters
Ionizing radiation:
High-energy electron beams
83
As a protection against ________, the postal service often uses electron beam radiation to sterilize certain classes of ____
- bioterrorism
- mail
84
- has a longer wavelength
- usually greater than about 1 nm
Nonionizing radiation
85
Nonionizing radiation
Damage to DNA
86
Best example of nonionizing radiation
Ultraviolet (UV) light
87
It inhibit correct replication of the DNA during cell reproduction
Thymine dimers
88
The UV wavelengths most effective for killing microorganisms are about
260 nm
89
A UV, or ________ lamp is commonly found in hospital rooms, nurseries, operating rooms, and cafeterias
germicidal
90
UV light is also used to disinfect _______ and other ______ _______
- vaccines
- medical products
91
Disadvantage of UV light as a disindectant
the radiation is not very penetrating
92
Potential problem of UV light
- can damage human eyes
- prolonged exposure can cause burns and skin cancer in humans
93
It does not have much direct effect on microorganisms
Microwave
94
Preservation
- short term
- long term
95
Short term
- replace sterile rubber cup (aseptically)
- put sterile mineral oil/glycerol (6 months to 1 year)
96
Long term
- liquid nitrogen
- lyophilization
