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MCB 2610 > EXAM 2- Chapter 7- part 4 > Flashcards

EXAM 2- Chapter 7- part 4 Flashcards

1
Q

What is sterilization?

A

Destruction or removal of all viable organisms

It is the most comprehensive level of microbial control.

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2
Q

What are disinfectants?

A

Substances that kill, inhibit, or remove disease-causing organisms
used on inanimate objects

Used primarily on inanimate objects.

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3
Q

What is sanitization?

A

Reduction of microbial population to meet some standard

Aimed at lowering the microbial load.

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4
Q

What is antisepsis?

A

Destruction or inhibition of microorganisms on living tissue

Antiseptics are used for this purpose.

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5
Q

What are antiseptics?

A

Substances used on living tissue to prevent sepsis

Typically used at lower concentrations than disinfectants.

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6
Q

What is chemotherapy in the context of microbiology?

A

Use of chemicals to kill or inhibit growth of microorganisms within host tissue

Aimed at treating infections.

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7
Q

Define antimicrobial agents.

A

Agents that kill microorganisms or inhibit their growth

Includes both cidal and static agents.

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8
Q

What are cidal agents?

A

Agents that kill microorganisms directly

Named after the specific organism they target.

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9
Q

What are static agents?

A

Agents that inhibit the growth of microorganisms

Allowing the immune system time to respond.

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10
Q

What influences the efficacy of antimicrobial agents?

A

population size and composition
concentration/intesity of agent
contact time
temperature
local environment

Each factor affects how effective an agent will be.

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11
Q

How does population size affect efficacy of antimicrobial agents?

A

Larger populations take longer to kill than smaller populations

Death occurs exponentially.

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12
Q

How does population composition affect efficacy of antimicrobial agents?

A

Microorganisms differ in their sensitivity to antimicrobial agents

Factors include age of cells and presence of spores.

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13
Q

Fill in the blank: Higher concentrations or intensities of microbial agents usually kill more rapidly, but _______ is an exception.

A

ethanol

70% ethanol is most effective due to dehydration of cells.

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14
Q

What is contact time?

A

Duration of exposure to an antimicrobial agent

Longer exposure typically results in more organisms killed.

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15
Q

How does temperature affect efficacy of antimicrobial agents?

A

Higher temperatures usually increase the rate of killing

Heat increases molecular motion.

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16
Q

What is decimal reduction time (D-value)?

A

Time to kill 90% of microorganisms and spores in a sample under specific conditions

A lower D-value indicates a more effective agent.

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17
Q

Normal filtration

A

will remove all bacteria
to remove viruses requires ultrafiltration methods

Normal filtration removes bacteria; ultrafiltration is needed for viruses.

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18
Q

What is the role of N-95 masks?

A

Removes 95% of particles that are 0.3 micrometers or larger

Effective for protecting against aerosolized pathogens.

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19
Q

What is steam sterilization?

A

Effective against all types of microorganisms including spores
must be carried out above 100C which requires saturated steam under pressure

Requires saturated steam under pressure, typically done in an autoclave.

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20
Q

What is the purpose of indicator tape in autoclaving?

A

To verify that the correct temperature and pressure have been achieved

Changes color when conditions are met.

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21
Q

What cannot be sterilized in an autoclave?

A

Plastics, some metals, anything that repels water, and items that need to maintain structural integrity

Examples include oil/wax and certain papers.

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22
Q

What is pasteurization?

A

Disinfectant
Controlled heating at temperatures well below boiling to kill pathogens

Used for beverages like milk and beer.

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23
Q

How is dry heat sterilization different from moist heat sterilization?

A

less effective- Requires higher temperatures and longer exposure times

Effective for items that cannot be exposed to moisture.

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24
Q

What is UV radiation?

A

Disinfection
using electromagnetic radiation to control microbes

UV radiation does not kill spores.

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25
What wavelengths of UV radiation can damage DNA?
260-280 nm alpha and beta rays ## Footnote These wavelengths form thymine dimers.
26
What is one example of using UV radiation for disinfection?
Disinfecting air in lab hoods using direct sunlight to disinfect water ## Footnote Direct sunlight can also disinfect water.
27
What type of radiation is referred to as 'cold sterilization'?
Ionizing radiation ## Footnote Gamma radiation penetrates deep into objects.
28
What does ionizing radiation destroy?
Bacterial endospores ## Footnote Not always effective against viruses.
29
When to use ionizing radiation
* Sterilization of antibiotics * Sterilization of hormones * Sterilization of sutures * Sterilization of plastic disposable supplies * Sterilization of food
30
What is the disk-diffusion method used for?
Evaluating a disinfectant if zone of inhibition is present it is effective ## Footnote A zone of inhibition indicates effectiveness.
31
How do phenolics work?
Antiseptic and disinfectant denature proteins and disrupt cell membranes- aromatic rings can wiggle between membranes ## Footnote They denature proteins and disrupt cell membranes.
32
Where are phenolics commonly used?
With organic matter- active in presence of organic matter Hospital and laboratory disinfectants ## Footnote Example: tuberculocidal.
33
What are limitations of phenolics
Disagreeable odor can cause skin irritation ## Footnote Can cause skin irritation.
34
How do aldehydes work
Sporicidal and chemical sterilant highly reactive- react with DNA and proteins- randomly adds alpha groups ## Footnote They react with DNA and proteins.
35
Name two commonly used aldehyde agents.
* Formaldehyde * Glutaraldehyde
36
What do alcohols do?
Disinfectant and antiseptics; not sporocidal denature proteins and possibly disolve membrane lipids inactivate envelope viruses ## Footnote They denature proteins and dissolve membrane lipids.
37
What are the two most common alcohol agents?
* Ethanol * Isopropanol
38
What is the concentration range for effective alcohol use?
60-80%
39
How does iodine work?
Skin antiseptic; can also be used as sterilant oxidizes cell constituents and iodinates proteins at high conc. it can kill spores ## Footnote Iodophore oxidizes cell constituents.
40
What is a limitation of iodine as a disinfectant?
Can cause skin damage stains allergies can be a problem ## Footnote Stains and allergies may also be a problem.
41
What is chlorine used for?
Disinfectant as liquid, sterilant as gas oxidizes cell constituents and destroys vegetative bacteria/fungi Chlorine gas kills spores ## Footnote Destroys vegetative bacteria and fungi.
42
What is a limitation of chlorine?
Can react with organic matter to form carcinogenic compounds.
43
What do heavy metals do?
Combine with and inactivate proteins may also precipitate proteins- pull out of solution ## Footnote They may also precipitate proteins.
44
Name some examples of heavy metal ions.
* Mercury * Silver * Arsenic * Zinc * Copper
45
How do quaternary ammonium compounds work?
Disinfectant/antiseptic amphipathic organic cleasing agents that act as wetting agents and emulsifiers disrupt membranes and denatures proteins ## Footnote They are amphipathic organic cleansing agents.
46
What is a limitation of quaternary ammonium compounds?
Not effective against Mycobacterium tuberculosis or endospores can be inactivated by hard water and soap
47
What is ethylene oxide used for?
Sterilization of heat-sensitive materials ## Footnote It is microbiocidal and sporocidal.
48
What type of equipment is used for ethylene oxide sterilization?
Equipment resembling an autoclave.
49
What is a characteristic of ethylene oxide?
Very strong alkylating agent.
50
Name two other sterilizing gases.
* Beta propiolactone * Vaporized hydrogen peroxide
51
T/F Some agents can be used as both disinfetants and antiseptics
TRUE but are used at different concentrations Antiseptics are lower conc.
52
Why do you want to inhibit growth with static agents?
so immune system has time to amount a response keeps pathogens from getting out of hand
53
Four types of composition to consider for antimicrobial agent
1. old VS young cell- older are harder to kill-deploy defenses 2. mix of microorganism- spores harder to kill 3. mycolic acid content- high mycolic acid mircroorgs. harder to kill 4. Gram- gram-negative are harder to kill
54
How does concentration of agent affect efficacy of antimicrobial agents?
usually higher concentrations kill more rapidly EXCEPTION- EtOH
55
How does Contact time affect efficacy of antimicrobial agents?
longer exposure= more organisms killed gives agent more time to make its way into the population then into cells
56
What are environmental factors that impact effectiveness?
pH Viscosity- takes agents longer to move through environment Conc. of Organic Matter- some agents interact with organic mater before going to cells
57
Pattern of microbial death
microorganisms are not killed instantly population death usually occurs exponentially
58
T/F want a lower D-value
TRUE kills faster and is more effective
59
What are the three physical control methods?
filtration heat radiation
60
Limitations of normal filtration
large particles clog filters ultrafiltration requires high pressure viscous liquids dont filter well
61
Membrane filter sterilization
Removes microorganisms from heat sensitive liquids
62
When to use membrane filter sterilization?
when we cannot use heat to sterilize EX. antibiotics
63
High Efficiency particulate air (HEPA) filters
Disinfecting used in laminar flow biological safety cabinets removes 99.97& of particles 0.3 um or larger
64
How does HEPA filters work
physical and electrostatic interactions
65
When to use HEPA filters
with pathogens that can be aerosolized
66
Heat
proteins and nucleic acids are disrupted
67
Heat Example
boiling- disinfectant does not kill spores
68
Freezing
can stop biochemical reactions in microbes in the presence of a buffer
69
What happens when a buffer is not used for freezing?
ice crystals form and can damage cells
70
Autoclave- quality control
1. indicator tape 2. Ampules of geobacillus stearothermophilis
71
Autoclave- ampules
do this if using spore forming bacteria Put ampules on plate and if nothing grows autoclave is working
72
Why do we not want to overload autoclave
The steam cannot move over everything to sanitize if its over crowded
73
Tyndallization
intermittent sterilization- 30-60 min of steam repeated 3 times with 24 hr incubation between
74
How does tyndallization kill spores
Does not kill them in spore form forces spores to germinate into metabolic form then second blast either kills or further germinates
75
Problems with tyndallization
cant ever be sure all the spores have germinated and been killed
76
How pasteurization works
does not sterilize but kills pathogens present and slows spoilage time by reducing microbial load
77
What is pasteruization used for?
beverages milk beer
78
How does dry heat sterilization work?
oxidizes cell constituents and denatures proteins
79
When to use dry heat sterilization?
metals that rust things that repel water- oil/wax
80
Dry heat incinerator
bench top incinerators used to sterilize inoculating loops
81
How does UV radiation disinfect?
damages DNA and forms thymine dimers
82
ionizing radiation
sterilizing radiation/gamma radiation penetrates deep into objects
83
3types of chemical control methods
disinfection antisepsis sterilization
84
Examples of Phenolics
tuberculocidal- effective in presence of organic material and long lating triclosan (hand sanitizer)- bacteria can become resistant
85
Limitations of heavy metals
Effective but TOXIC
86
Why would we want to use Quaternary ammonia compounds?
safe and easy to use rarely causes irritation
87
What is refered to as cold sterilization
sterilizing gas Ethylene oxide

MCB 2610 (24 decks)

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