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Flashcards in Sterilization and Disinfection Deck (69):
0

What is sterilization?

Kills all forms of microbial life
It is desirable but not always feasible

1

What is antisepsis?

Prevents sepsis (infection) by killing infectious microorganisms

2

What is disinfection?

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

3

What is santization?

Reducing the number of microorganisms

4

What are sterilizers?

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

5

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

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

6

Is destruction of microorganisms equivalent to sterilization? Why?

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

7

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

Exponential
~30 minutes

8

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?

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

9

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

No

10

Kinetics vary with ______ populations

low

11

Kinetics are affected by composition of what?

Suspending medium
For example, aggregates of bacteria can survive longer

12

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

resistant

13

Endospores are formed in response to what?

Nutrient depletion

14

Spores contain everything necessary to

regenerate vegetative cells

15

What is the bacterial spore basis to resistance?

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

16

What does dipicolinic acid do?

Chelates Ca2+
Stabilizes DNA by intercalation

17

What specifically initiates sporulation?

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

18

Sigma factors are initiating proteins associated with what?

RNA polymerase

19

Sigma 29 is a sporulation specific factor of what bacteria?

B. subtilis

20

What is sigma 55?

Its for vegetative growth

21

What are the three stages of regeneration of vegetative cells?

Activation
Germination
Outgrowth

22

For the regeneration of vegetative cells, activation generally occurs by

heat or chemicals
(one possibility is the inactivation of a critical protein)

23

Describe the germination phase of regeneration of vegetative cells

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

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