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Micro Quiz 1 > disinfection and sterilization > Flashcards

disinfection and sterilization Flashcards

(73 cards)

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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
how is radiation most commonly applied?
with a UV light emitted by mercury vapor lamps = nonionizing radation
26
when is radiation used?
to decrease bacterial content of air in ORs, barracks, nurseries, restaurants, hospital wards, and animal rooms
27
how does radiation sterilize (mechanism)?
nucleic acids and proteins absorb UV wavelengths produces cross-linked thymine dimers in DNA interferes with DNA replication also causes toxic intracellular peroxide formation
28
what is the advantage of the UV? disadvantage?
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
29
when are X-rays used for sterilization?
more energetic - have been used in food sterilization, but results questionable
30
how would drying lower bacterial levels?
water needed for bacterial growth
31
how would high osmotic pressure reduce bacterial levels?
high salt can dry out microbes | high sugar acts as a preservative
32
what do chemical sterilization methods do (generally)?
interact with lipids, proteins, or DNA
33
what determines the rate of killing of chemical methods of sterilization?
for most, rate increases with concentration and length of exposure
34
what is gaseous sterilization? what is it used for?
ethylene oxide = alkylating agent | used to sterilize heat-sensitive materials (esp plastics)
35
what are the advantages and disadvantages of gaseous sterilization?
reliable suitable only for dry materials toxic to humans needs special equipment explosive if pure so used only in presence of high CO2
36
when in gaseous sterilization used?
plasticware surgical equiptment hospital bedding materials handled by patients
37
what is the widest used chemical sterilization method?
ethanol
38
what is the optimum concentration of ethanol for sterilization?
60-70%
39
how does ethanol sterilize?
denatures proteins
40
what are the advantages of ethanol versus isopropyl alcohol?
ethanol has legal restrictions on use isopropyl alcohol doesn't have those, slightly more potent, less volatile, but more expensive
41
when is ethanol used?
commonly on skin before infections in tinctures of antiseptics and germicides in jars where thermometers are stored
42
what does ethanol kill?
does not kill spores
43
what halogens are used for sterilization?
iodine | chlorine
44
what does tincture of iodine consist of?
iodine in water-ethanol solution | contains iodine and KI
45
how does tincture of iodine sterilize?
oxidizes the hydroxyl group of reactive tyrosine residues
46
when is tincture of iodine used?
reliable skin antiseptic used for minor wounds (but hurts) with detergents, used to prepare skin before surgery
47
when is chlorine used?
``` as a gas in water supplies and swimming pools as hypochlorite solutions by food and dairy industries to clean surfaces ```
48
what is the advantage of chlorine?
in the food industry, traces rapidly lost or destroyed, leaving no odor or flavor
49
how does chlorine sterilize?
oxidizes cysteine sulfydryl groups
50
what bacteria are cationic detergents effective against?
all kinds of bacteria
51
how do cationic detergents work?
disrupt cell membranes and dissolve lipid films that may protect bacteria
52
what are the most effective cationic detergents?
quaternary ammonium salts | have three short chain alkyl grous and a long chain alkyl group
53
why don't anionic detergents work well?
the molecules are repelled by the negative charge of the bacterial surface
54
what are the advantages of cationic detergents?
leave a bacteriocidal film work at low concentrations usually non-irritating
55
what do cationic detergents not work against?
not active against pseudomonas | poorly active against mycobacterium tuberculosis
56
what oxidizing agents are used for sterilization?
hydrogen peroxide | potassium permanganate
57
when is hydrogen peroxide used?
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
what antagonizes hydrogen peroxide action?
catalase | all staphylococci are catalase positive
59
when is potassium permanganate used?
as a urethral antiseptic
60
what is the mechanism of action of phenols?
denature proteins
61
when are phenols used?
to spray surgical operating rooms
62
what are the advantages and disadvantages of phenols?
kills wide variety of bacteria | but needs high concentrations
63
when are substituted phenols used?
as skin antiseptics in antibacterial soaps as a textile preservative
64
what do soaps effectively do?
remove bacteria and dirt from skin surfaces - only weakly bacteriocidal
65
what can make soaps antibacterial?
triclosan = antibacterial agent
66
how does triclosan work? what are the disadvantages?
inhibits specific step in lipid biosynthesis | resistant mutants can be isolated
67
how are heavy metals used to sterilize?
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
how do heavy metals sterilize?
bind to SH groups in proteins
69
how are dyes used to sterilize?
genetian violet = antifungal agent | used for candida and tinea (athletes foot)
70
what aldehydes are used to sterilize?
formaldehyde | glutaraldehyde
71
what is formaldehyde used for?
in vaccines
72
what is glutaraldehyde used for?
to treat areas wehre blood samples and used syringes are present - kills hepatits
73
what can be used to preserve food?
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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