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Micro Quiz 1 > disinfection and sterilization > Flashcards

disinfection and sterilization Flashcards

1
Q

what is sterilization?

A

killing of all microorganisms (bacteria, fungi, viral).

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2
Q

what is a germicide?

A

agent used to kill bacteria

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3
Q

what is antisepsis?

A

application of chemical agents to the surface of the human body to kill of inhibit pathogenic bacteria

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4
Q

what does it mean for something to be septic?

A

characterized by the presence of pathogenic bacteria in living tissue

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5
Q

what does it mean for something to be aseptic?

A

without pathogenic bacteria

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6
Q

what does it mean to sanitize something?

A

lower bacterial content of food utensils or similar objects wtihout necessarily killing all bacteria (ie dishes washed in hot water and soap)

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7
Q

what is a preservative?

A

agent used in small (non-toxic) concentrations to inhibit the growth of organisms in, for example, food or vaccines

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8
Q

what is the phenol coefficient?

A

measure of the killing capacity of an agent, compared with phenol
ration of the minimal killing concentration of phenol to that of the agent
agent that works at concentrations lower than the killing concentration of phenol has a coefficient much greater than one

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9
Q

what are the three main physical agents used for sterilization, etc.?

A

in order of importance:

1: heat (wet or dry)
2: filtration
3: radiation (UV, gamma rays)

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10
Q

what types of heat are most effective?

A

wet heat (such as steam) is much more effective than dry heat because water molecules speed the denaturation of bacterial proteins by providing H bonds to replace those normally in the proteins - heated water molecules disrupt the H bonds

with dry heat, need greater time and temp for sterilization

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11
Q

what does an autoclave do?

A

provides standard conditions for complete killing of all bacteria (including spores)
live steam under pressure

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12
Q

what are the advantages and disadvantages of autoclaves?

A

advantages: assurance of complete sterilization
disadvantages: requires complicated equipment, unsuitable for heat-sensitive materials

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13
Q

what are the advantages and disadvantages of using dry heat?

A

takes longer and need higher temps

good for materials that would be damaged by water such as powders or surgical dressings

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14
Q

what are the advantages and disadvantages of using boiling water to sterilize?

A

kills most bacteria but not spores

but fast - five to ten minutes
simple equipment and is convenient

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15
Q

what is pasteurization?

A

heating of milk or other liquids to sterilize - reduces total bacterial count to 1-3% of initial level
63 degrees for 30 minutes

does not kill spores

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16
Q

what is high temperature short time? when is it used?

A

HTST - flash pasteurization
higher temps than normal pasteurization but much shorter (15-17 seconds)

used in juices and in milk sometimes in the US, method of choice for milk in europe and asia

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17
Q

how do you determine if milk has been sufficiently pasteurized?

A

if it tests negative for alkaline phosphatase - enzyme denatures under conditions similar to those that kill C. burnetii (which was what was originally tested for)

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18
Q

when would you use filtration?

A

when the liquid material to be sterilized is sensitive to heat (so can’t heat sterilize)

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19
Q

what are the advantages and disadvantages of filtration?

A

nondestructive but inconvenient, esp. for large volumes

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20
Q

where is filtration commonly used?

A

pharmaceutical industries have automated it

can also use presterilized, disposable filters that attach to a syringe in hospital and lab settings

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21
Q

what is commonly sterilized via filtration?

A

many vaccines, drugs,

kept in sealed, rubber-capped vials

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22
Q

how does filtration work?

A

run liquid through filter - bacteria too big to get through filter

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23
Q

what determines flow rate in filtration?

A

pore size
pressure applied
whether bacteria or other solids have begun to clog pores

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24
Q

what can not be removed via filtration?

A

a few types of bacteria can get through pores of .45 microns

none can get through .22 micron pores, but viruses can

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25
Q

how is radiation most commonly applied?

A

with a UV light emitted by mercury vapor lamps = nonionizing radation

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26
Q

when is radiation used?

A

to decrease bacterial content of air in ORs, barracks, nurseries, restaurants, hospital wards, and animal rooms

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27
Q

how does radiation sterilize (mechanism)?

A

nucleic acids and proteins absorb UV wavelengths
produces cross-linked thymine dimers in DNA
interferes with DNA replication

also causes toxic intracellular peroxide formation

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28
Q

what is the advantage of the UV? disadvantage?

A

simple to set up
can be left on for a long time
need little attention

poor capacity to penetrate anything but air and the thinnest layers of solids and liquids (won’t penetrate glass)
can irritate and damage human tissues

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29
Q

when are X-rays used for sterilization?

A

more energetic - have been used in food sterilization, but results questionable

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30
Q

how would drying lower bacterial levels?

A

water needed for bacterial growth

31
Q

how would high osmotic pressure reduce bacterial levels?

A

high salt can dry out microbes

high sugar acts as a preservative

32
Q

what do chemical sterilization methods do (generally)?

A

interact with lipids, proteins, or DNA

33
Q

what determines the rate of killing of chemical methods of sterilization?

A

for most, rate increases with concentration and length of exposure

34
Q

what is gaseous sterilization? what is it used for?

A

ethylene oxide = alkylating agent

used to sterilize heat-sensitive materials (esp plastics)

35
Q

what are the advantages and disadvantages of gaseous sterilization?

A

reliable

suitable only for dry materials
toxic to humans
needs special equipment
explosive if pure so used only in presence of high CO2

36
Q

when in gaseous sterilization used?

A

plasticware
surgical equiptment
hospital bedding
materials handled by patients

37
Q

what is the widest used chemical sterilization method?

A

ethanol

38
Q

what is the optimum concentration of ethanol for sterilization?

A

60-70%

39
Q

how does ethanol sterilize?

A

denatures proteins

40
Q

what are the advantages of ethanol versus isopropyl alcohol?

A

ethanol has legal restrictions on use

isopropyl alcohol doesn’t have those, slightly more potent, less volatile, but more expensive

41
Q

when is ethanol used?

A

commonly on skin before infections
in tinctures of antiseptics and germicides
in jars where thermometers are stored

42
Q

what does ethanol kill?

A

does not kill spores

43
Q

what halogens are used for sterilization?

A

iodine

chlorine

44
Q

what does tincture of iodine consist of?

A

iodine in water-ethanol solution

contains iodine and KI

45
Q

how does tincture of iodine sterilize?

A

oxidizes the hydroxyl group of reactive tyrosine residues

46
Q

when is tincture of iodine used?

A

reliable skin antiseptic
used for minor wounds (but hurts)
with detergents, used to prepare skin before surgery

47
Q

when is chlorine used?

A 
as a gas
in water supplies and swimming pools
as hypochlorite solutions
by food and dairy industries
to clean surfaces
48
Q

what is the advantage of chlorine?

A

in the food industry, traces rapidly lost or destroyed, leaving no odor or flavor

49
Q

how does chlorine sterilize?

A

oxidizes cysteine sulfydryl groups

50
Q

what bacteria are cationic detergents effective against?

A

all kinds of bacteria

51
Q

how do cationic detergents work?

A

disrupt cell membranes and dissolve lipid films that may protect bacteria

52
Q

what are the most effective cationic detergents?

A

quaternary ammonium salts

have three short chain alkyl grous and a long chain alkyl group

53
Q

why don’t anionic detergents work well?

A

the molecules are repelled by the negative charge of the bacterial surface

54
Q

what are the advantages of cationic detergents?

A

leave a bacteriocidal film
work at low concentrations
usually non-irritating

55
Q

what do cationic detergents not work against?

A

not active against pseudomonas

poorly active against mycobacterium tuberculosis

56
Q

what oxidizing agents are used for sterilization?

A

hydrogen peroxide

potassium permanganate

57
Q

when is hydrogen peroxide used?

A

as a 3% solution, infrequently used to treat wound infections, esp. deep ones that may contain anaerobes

to control growth of the plethora of anaerobic bacteria that grow in gingivial crevices of the gums

58
Q

what antagonizes hydrogen peroxide action?

A

catalase

all staphylococci are catalase positive

59
Q

when is potassium permanganate used?

A

as a urethral antiseptic

60
Q

what is the mechanism of action of phenols?

A

denature proteins

61
Q

when are phenols used?

A

to spray surgical operating rooms

62
Q

what are the advantages and disadvantages of phenols?

A

kills wide variety of bacteria

but needs high concentrations

63
Q

when are substituted phenols used?

A

as skin antiseptics
in antibacterial soaps
as a textile preservative

64
Q

what do soaps effectively do?

A

remove bacteria and dirt from skin surfaces - only weakly bacteriocidal

65
Q

what can make soaps antibacterial?

A

triclosan = antibacterial agent

66
Q

how does triclosan work? what are the disadvantages?

A

inhibits specific step in lipid biosynthesis

resistant mutants can be isolated

67
Q

how are heavy metals used to sterilize?

A

example = silver salts = 1% solution of silver nitrate - put in eyes of newborns to kill gonococcal organisms

mercurial compounds in organic form can be used on minor skin wounds

68
Q

how do heavy metals sterilize?

A

bind to SH groups in proteins

69
Q

how are dyes used to sterilize?

A

genetian violet = antifungal agent

used for candida and tinea (athletes foot)

70
Q

what aldehydes are used to sterilize?

A

formaldehyde

glutaraldehyde

71
Q

what is formaldehyde used for?

A

in vaccines

72
Q

what is glutaraldehyde used for?

A

to treat areas wehre blood samples and used syringes are present - kills hepatits

73
Q

what can be used to preserve food?

A

short chain FA and organic acids

eg. lactic acid in pickles and sauerkraut
acetic acid in pickles and relishes
propionic acid in bread (prevents mold growth)
benzoic acid in pharmaceuticals and food
natural phenolics (tymol; eugenol) as mild antiseptics and preservatives
smoked foods covered and partially penetrated by phenolic compounds from wood smoke

Micro Quiz 1 (9 decks)

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