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Microbiology > Sterilization and Disinfection > Flashcards

Sterilization and Disinfection Flashcards

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0
Q

What is antisepsis?

A

Prevents sepsis (infection) by killing infectious microorganisms

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1
Q

What is sterilization?

A

Kills all forms of microbial life

It is desirable but not always feasible

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2
Q

What is disinfection?

A

Same as antisepsis (preventing sepsis by killing microorganisms) except applied to inanimate objects

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3
Q

What is santization?

A

Reducing the number of microorganisms

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4
Q

What are sterilizers?

A

They are used to eliminate all forms of microbial life including fungi, viruses, bacteria, and their spores

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5
Q

What are antiseptics and germicides and how are they different from disinfectants?

A

Antiseptics and germicides are used on humans/animals to inhibit growth of microorganisms and they are regulated by the FDA. Disinfectants are used on hard inanimate surfaces

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6
Q

Is destruction of microorganisms equivalent to sterilization? Why?

A

No, killing microorganisms in an intravenous solution could release pyrogenic compounds causing toxic shock
Solutions should be sterilized so that bacteria never have the chance to grow

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7
Q

Death rates of bacteria during sterilization follow what trend? How long does it take phenol to kill bacteria down to 1% of the population?

A

Exponential

~30 minutes

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8
Q

Death rate of spores follow what trend? How long does it take phenol to kill spores down to 1% of the population? What is the rate constant compared to death of bacteria?

A

Exponential but much slower
~6 hours
Rate constant is 1000 fold less
Killing spores is a major problem

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9
Q

During sterilization, is there an absolute time when 0 organisms remain?

A

No

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10
Q

Kinetics vary with ______ populations

A

low

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11
Q

Kinetics are affected by composition of what?

A

Suspending medium

For example, aggregates of bacteria can survive longer

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12
Q

Bacterial spores are relatively __________ to killing by all means of sterilization

A

resistant

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13
Q

Endospores are formed in response to what?

A

Nutrient depletion

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14
Q

Spores contain everything necessary to

A

regenerate vegetative cells

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15
Q

What is the bacterial spore basis to resistance?

A

Extremely low water content (and high Ca2+) due to dipicolinic acid

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16
Q

What does dipicolinic acid do?

A

Chelates Ca2+

Stabilizes DNA by intercalation

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17
Q

What specifically initiates sporulation?

A

GTP deficiency

An unfavorable environment leads to decreased amino acids which leads to increased ppGpp, inhibiting GTP synthesis

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18
Q

Sigma factors are initiating proteins associated with what?

A

RNA polymerase

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19
Q

Sigma 29 is a sporulation specific factor of what bacteria?

A

B. subtilis

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20
Q

What is sigma 55?

A

Its for vegetative growth

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21
Q

What are the three stages of regeneration of vegetative cells?

A

Activation
Germination
Outgrowth

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22
Q

For the regeneration of vegetative cells, activation generally occurs by

A

heat or chemicals

one possibility is the inactivation of a critical protein

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23
Q

Describe the germination phase of regeneration of vegetative cells

A

Irreversible
Requires water
Accompanied by loss of resistance
Doesn’t require nucleic acid or protein synthesis

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24
During the outgrowth stage of regeneration of vegetative cells, there is active what?
Biosynthesis
25
There are four medically important species of anaerobic spore-forming bacteria are what?
C. tetani - tetanus C. botulinum - botulism C. perfringens - gas gangrene C. difficile - diarrhea
26
C. difficile exists as vegetative cells or spores?
Both
27
Which form of C. difficile produces the toxin?
Vegetative form
28
What is the main mode of transmission for C. difficile?
Spores Survive on dry surfaces for several months Resistant to heat, antibiotics, acid, and alcohol hand disinfectants
29
What happens after ingestion of C. difficile?
Spores germinate into vegetative cells in the colon and produce toxin
30
Are alcohol disinfectants effective against C. difficile? What can you do?
No, just don't come into contact with it (gloves, gowns, etc)
31
What are 3 chemical agents that damage the cell membrane?
Surface active compounds Phenolic compounds Alcohols
32
What are surface active compounds?
``` Detergents Cationic agents (Zephiran) Anionic agents (SDS) Nonionic agents (Tween 80) ```
33
Are nonionic agents effective?
No, they can even serve as nutrients for bacterial growth
34
Two examples of alkyl and chloro phenols (which are less potent than pure phenol)?
Lysol | Triclosan
35
Example of a halogenated diphenyl?
hexachlorophene (soap withdrawn from OTC sales because falsely accused of being carcinogenic)
36
What is the optimal ethanol concentration to kill bacteria? Why not 100%?
50-70%, any higher than that the bacteria become dehydrated and they are harder to kill
37
Is isopropanol more or less effective than ethanol?
More, but its more toxic as well
38
Does alcohol kill spores?
Nope
39
What are the organic acids benzoic and proprionic used for?
They denature bacterial proteins and are used in preservatives and pharmaceuticals
40
Alkyl esters of organic acids (benzoic and proprionic) act like alkyl-substituted phenols. Why aren't they toxic once ingested?
They are rapidly hydrolyzed to p-hydroxy-benzoate
41
What are four things that modify proteins and nucleic acids of bacteria directly?
Heavy metals Oxidizing agents Dyes Alkylating agents
42
How do heavy metals act on bacteria? How can they be reversed?
They interact with sulfhydryl groups (many if not most proteins have these) They are effective at low concentrations (1 ppm) Reversed by sulfhydryl compounds
43
What are silver nitrate and silver sulfadiazine used for?
Silver nitrate is used in the eyes of newborns to prevent gonococcal infections Silver sulfadiazine is used to prevent skin infections in burn patients
44
Is iodine an oxidizing agent? How does it work?
Yes | It combines with proteins and iodinates tyrosine residues
45
In what form is iodine used? What makes it less painful?
KI is used but it is very painful and destructive | Combining it with a detergent (iodophores-betadyne)
46
What is iodine effective against?
Spores
47
Do hydrogen peroxide and organic peroxides work better on anaerobes or aerobes? Why?
Anaerobes because they lack catalase
48
Cl and hypochlorite oxidizing agents yield what? What are they used on?
``` Hypochlorous acid (HOCl) Inanimate objects ```
49
What are the names of two types of dyes?
Triphenylmethanes | Acridines
50
What are triphenylmethanes?
Topical skin treatment dyes - used on burn patients | Crystal violet, brilliant green, malachite green
51
What are acridines?
Used for wound antisepsis Mutagenic - insert into DNA Carcinogenic Proflavine, acriflavine
52
What are alkylating agents, how do they work?
Active against spores at level equivalent to those necessary to kill vegetative cells Used often, effective They work by interacting with reactive species, killing enzymes Formaldehyde, glutaraldehyde, ethylene oxide
53
What does formaldehyde, an alkylating agent, react with?
CO2-, SH, OH
54
What are the two ways that formaldehyde can be used, and what specific use does it have?
As an aqueous solution it is formalin (37% soln) 0.2-0.4% is used to inactivate virus to make vaccines Also used as a gas for decontamination It is carcinogenic
55
Glutaraldehyde: what does it react with, what is it used for?
Reacts with SH and NH groups Cold sterilant for surgical items (or whatever) that won't hold up in heat 10x as effective as formaldehyde
56
Ethylene oxide: what is it used for?
It is extremely reactive, biohazard | Used by companies that make hospital equipment
57
Sterilization with heat is dependent on which factors?
Time, temperature, pressure, water
58
Is sterilization with heat slower or faster without water?
Slower without water
59
What is tyndallization?
Fractional sterilization method Heat to 80-100 degrees C for 30 mins for 3 days Spores activated each cycle then killed
60
What is pasteurization?
Reduces the number of microorganisms and kills most pathogens Heat to 62 degrees C for 30 minutes
61
Should freezing/thawing be used for sterilization?
No
62
What can damage skin and eyes but has low penetrating power?
UV radiation
63
What produces pyrimidine dimers in DNA? What are they repaired by?
UV radiation | Photoreactivation or SOS repair
64
What is UV radiation used for?
Sanitizing rooms and tissue culture hoods
65
What is ionizing radiation used for?
Sterilization of surgical supplies and food, kills spores with the direct effect
66
What is the direct effect of ionizing radiation?
Energy directly damages macromolecules and kills spores
67
What is the indirect effect of ionizing radiation?
Ionization of H2O | Doesn't kill spores
68
What pore size would you use to filter bacteria out of liquids?
0.22 microns

Microbiology (10 decks)

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