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Microbiology > Sterilization and Disinfection > Flashcards

Sterilization and Disinfection Flashcards

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Biology 101 flashcards
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
Q

During the outgrowth stage of regeneration of vegetative cells, there is active what?

A

Biosynthesis

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25
Q

There are four medically important species of anaerobic spore-forming bacteria are what?

A

C. tetani - tetanus
C. botulinum - botulism
C. perfringens - gas gangrene
C. difficile - diarrhea

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26
Q

C. difficile exists as vegetative cells or spores?

A

Both

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27
Q

Which form of C. difficile produces the toxin?

A

Vegetative form

28
Q

What is the main mode of transmission for C. difficile?

A

Spores
Survive on dry surfaces for several months
Resistant to heat, antibiotics, acid, and alcohol hand disinfectants

29
Q

What happens after ingestion of C. difficile?

A

Spores germinate into vegetative cells in the colon and produce toxin

30
Q

Are alcohol disinfectants effective against C. difficile? What can you do?

A

No, just don’t come into contact with it (gloves, gowns, etc)

31
Q

What are 3 chemical agents that damage the cell membrane?

A

Surface active compounds
Phenolic compounds
Alcohols

32
Q

What are surface active compounds?

A 
Detergents
Cationic agents (Zephiran)
Anionic agents (SDS)
Nonionic agents (Tween 80)
33
Q

Are nonionic agents effective?

A

No, they can even serve as nutrients for bacterial growth

34
Q

Two examples of alkyl and chloro phenols (which are less potent than pure phenol)?

A

Lysol

Triclosan

35
Q

Example of a halogenated diphenyl?

A

hexachlorophene (soap withdrawn from OTC sales because falsely accused of being carcinogenic)

36
Q

What is the optimal ethanol concentration to kill bacteria? Why not 100%?

A

50-70%, any higher than that the bacteria become dehydrated and they are harder to kill

37
Q

Is isopropanol more or less effective than ethanol?

A

More, but its more toxic as well

38
Q

Does alcohol kill spores?

A

Nope

39
Q

What are the organic acids benzoic and proprionic used for?

A

They denature bacterial proteins and are used in preservatives and pharmaceuticals

40
Q

Alkyl esters of organic acids (benzoic and proprionic) act like alkyl-substituted phenols. Why aren’t they toxic once ingested?

A

They are rapidly hydrolyzed to p-hydroxy-benzoate

41
Q

What are four things that modify proteins and nucleic acids of bacteria directly?

A

Heavy metals
Oxidizing agents
Dyes
Alkylating agents

42
Q

How do heavy metals act on bacteria? How can they be reversed?

A

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
Q

What are silver nitrate and silver sulfadiazine used for?

A

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
Q

Is iodine an oxidizing agent? How does it work?

A

Yes

It combines with proteins and iodinates tyrosine residues

45
Q

In what form is iodine used? What makes it less painful?

A

KI is used but it is very painful and destructive

Combining it with a detergent (iodophores-betadyne)

46
Q

What is iodine effective against?

A

Spores

47
Q

Do hydrogen peroxide and organic peroxides work better on anaerobes or aerobes? Why?

A

Anaerobes because they lack catalase

48
Q

Cl and hypochlorite oxidizing agents yield what? What are they used on?

A 
Hypochlorous acid (HOCl)
Inanimate objects
49
Q

What are the names of two types of dyes?

A

Triphenylmethanes

Acridines

50
Q

What are triphenylmethanes?

A

Topical skin treatment dyes - used on burn patients

Crystal violet, brilliant green, malachite green

51
Q

What are acridines?

A

Used for wound antisepsis
Mutagenic - insert into DNA
Carcinogenic
Proflavine, acriflavine

52
Q

What are alkylating agents, how do they work?

A

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
Q

What does formaldehyde, an alkylating agent, react with?

A

CO2-, SH, OH

54
Q

What are the two ways that formaldehyde can be used, and what specific use does it have?

A

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
Q

Glutaraldehyde: what does it react with, what is it used for?

A

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
Q

Ethylene oxide: what is it used for?

A

It is extremely reactive, biohazard

Used by companies that make hospital equipment

57
Q

Sterilization with heat is dependent on which factors?

A

Time, temperature, pressure, water

58
Q

Is sterilization with heat slower or faster without water?

A

Slower without water

59
Q

What is tyndallization?

A

Fractional sterilization method
Heat to 80-100 degrees C for 30 mins for 3 days
Spores activated each cycle then killed

60
Q

What is pasteurization?

A

Reduces the number of microorganisms and kills most pathogens
Heat to 62 degrees C for 30 minutes

61
Q

Should freezing/thawing be used for sterilization?

A

No

62
Q

What can damage skin and eyes but has low penetrating power?

A

UV radiation

63
Q

What produces pyrimidine dimers in DNA? What are they repaired by?

A

UV radiation

Photoreactivation or SOS repair

64
Q

What is UV radiation used for?

A

Sanitizing rooms and tissue culture hoods

65
Q

What is ionizing radiation used for?

A

Sterilization of surgical supplies and food, kills spores with the direct effect

66
Q

What is the direct effect of ionizing radiation?

A

Energy directly damages macromolecules and kills spores

67
Q

What is the indirect effect of ionizing radiation?

A

Ionization of H2O

Doesn’t kill spores

68
Q

What pore size would you use to filter bacteria out of liquids?

A

0.22 microns

Microbiology (10 decks)

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