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Infection & Immunity > Sterilisation & Contamination > Flashcards

Sterilisation & Contamination Flashcards

1
Q

what is the definition of sterile

A

free from all viable forms of life

population never reaches zero

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2
Q

what does SAL stand for

A

sterility level assurance

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3
Q

what does PNSU stand for

A

probability of a non-sterile unit

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4
Q

what is the bioburden

A

how many bacteria are in a product before sterilisation and what level of contamination is acceptable

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5
Q

what level of contamination is acceptable

A

1 in 10^6

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6
Q

what are industry disadvantages of long sterilisation times

A

drug may degrade

process is time consuming and expensive

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7
Q

what is the process of sterilisation

A
  1. destruction- flaming/chemical oxidation (not practical for pharmaceutical products)
  2. killing/inactivation - used in most methods, may not remove endotoxins
  3. removing- filtration or centrifugation *not reliable for pharmaceutics)
    steam sterilisation is most effective and reliable
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8
Q

what sterilisation processes are in the European Pharmacopeia

A

steam sterilisation, dry heat, ionising radiation, gaseous sterilisation, filtration

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9
Q

what is moist heat sterilisation

A

involves steam at 121-134 degrees C

very effective with widespread application

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10
Q

what is moist heat sterilisation used for

A

dressings, sheets, equipment, containers, aqueous injections, ophthalmic preparations, contaminated waste materials

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11
Q

what is dry heat sterilisation

A

usually in the 160-180 range

less effective than moist heat sterilisation

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12
Q

what is dry heat sterilisation used for

A

glasswear, metal surgical instruments, non-aqueous thermostable liquids, thermostable powders

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13
Q

how is radiation used in sterilisation

A

gamma rays, accelerated electrons, x-rays and uv are used
alternate method for heat sensitive products
mainly for articles in dried state

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14
Q

what articles is radiation used to sterilise

A

surgical instruments, sutures, plastic syringes, dry pharmaceutical products

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15
Q

what is gaseous sterilisation

A

uses ethylene oxide or fomaldehyde

only used for heat sensitive items

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16
Q

what products are gaseous sterilisation used for

A

reusable surgical instruments, medical/diagnostic equipment, surface sterilisation of powders

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17
Q

what is filtration

A 
for sterilisation (0.2 to 0.22 micron) filters
removes particulates from gases and liquids
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18
Q

what is the only process that removes microorganisms

A

filtration

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19
Q

what articles is filtration used for

A

heat sensitive injections, ophthalmic preparations, biological products, air/gases to supply asceptic areas

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20
Q

what are the limiting factors of sterilisation processes

A

cost, nature of product and nature of microbial contamination

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21
Q

what is terminal sterilisation

A

product is sterilised in its final container

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22
Q

what is asceptic processing

A

using pre-sterilised components to assemble the product, required a clean room

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23
Q

what does the initial shoulder of a survival curve indicate

A

clumping - so each cell needs to be ‘hit’ before CFU goes from 1 to 0
repair mechanisms in cell - some need to be ‘hit’ twice to result in death

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24
Q

what does a tailing curve graph show

A

initial exponential phase then flatter
mixed population - different bacteria present, each with different resistance to sterilisation process
protective effects - lysis of cells protects surviving cells

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25
Q

what does an activated survival curve look like

A

initial hump but then exponential

germination of spores upon heat stimulation

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26
Q

what is a D value

A

decimal reduction time - time needed to reduce population factor by 10
can be used for heat and radiation, refers to specific temperature or radiation dose

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27
Q

what is a z value

A

the increase in temperature needed to reduce the D value ten fold
only used in heat sterilisation

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28
Q

what is the equation used to find a D value

A

D= t2-t1
———–
logN1-logN2

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29
Q

what is the equation used to find a Z value

A

Z= t2-t1
———–
logD1-logD2

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30
Q

what is the inactivation rate constant

A

k= 2.303/D

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31
Q

what does Q10 mean

A

change in k from a 10degree change in temp

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32
Q

what does IF stand for

A

inactivation factor

measure of total microbial inactivation

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33
Q

what does F0 mean

A

equivalent time of moist sterilisation at 121degrees with a Z value of 10degrees

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34
Q

what is autoclaving

A

moist heat with temp >100degreesC only achieved under pressure
organisms killed by temp, time, hydration

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35
Q

what is superheated steam

A

water in the vapour phase and behaves like a gas

pressure decreases if temp decreases

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36
Q

what is supersaturated steam

A

in liquid phase and is made up of small droplets of water held in suspension by convection currents

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37
Q

what is dry saturated steam

A

exists only on the phase boundary

will condense if temp is lowered

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38
Q

what form of steam is suitable for sterilisation

A

only dry saturated steam

due to release of heat, hydration and penetration

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39
Q

what happens in the release of heat stage of moist heat sterilisation

A

sensible heat when exchanged, results in change in temperature
latent heat; when exchanged, results in change of physical state- no temp change

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40
Q

what type of heat does supersaturated steam release

A

sensible heat

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41
Q

what type of heat does superheated steam release

A

sensible and latent, but only releases sensible heat in absence of condensation

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42
Q

what type of heat does dry saturated steam release

A

both sensible and latent heat

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43
Q

what is the second step of moist heat sterilisation

A

hydration

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44
Q

what happens in the hydration stage of moist heat sterilisation

A

dry saturated steam = moist heat reaction (rapid heat transfer)
superheated steam= dry heat reaction (oxidation, slower heat transfer)

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45
Q

what is the third stage of moist heat sterilisation

A

penetration

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46
Q

what happens in the penetration stage of moist heat sterilisation

A

dry saturated steam and condensation causes a local vacuum and rapid penetration of spores
superheated steam and no condensation means no vacuum so no penetration

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47
Q

what are the advantages of a large scale autoclave

A

they prevent wet steam formation
they have a jacket to assist with heat retention or cooling
they have a boiler and heating coils
they have a separate boiler and autoclave

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48
Q

how do large scale autoclaves work

gravity displacement autoclave

A

gravity displacement- steam added from top and air removed from bottom
used for lab media, water, pharmaceutical products, waste, non-porous items
not suitable for porous loads as air may become entrapped in packaging or material

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49
Q

how do large scale autoclaves work

porous load autoclave

A

vacuum assisted
fitted with vacuum pump to remove air before adding steam
used for dressings, wrapped or hollow instruments

50
Q

what are the stages of autoclaving

A

air removal and steam admission, heating up/exposure, drying and coolung (porous loads may get damp; drying by vacuum and heat from outer jacket) cooling necessary to shorten the cycle (pumping water through jacket or spray cooling)

51
Q

what is air ballasting

A

sterile fluids can be packaged in flexible plastic containers
pressure in airspace above fluid may lead to bursting
to prevent this, some air may be retained to create overpressure in specifically designed autoclaves
to prevent layering of air, such autoclaves may require fan or spraying mechanism to mix air and steam

52
Q

what are some problems with sterilising

A

superheated steam- too dry/overheating/excessive pressure reduction/hydration of over-dried fabrics
air in steriliser

53
Q

what is the effect of air in an autoclave

A

with steam/air mixtures, total pressure is equal to sum of partial pressures, which are proportional to relative amount of steam and aire present
1. unjacketed bench autoclave, 2. jacketed autoclave, 3. layering

54
Q

what are the effects of an unjacketed bench autoclave

A

usually only controlled by pressure

air leads to lower temp

55
Q

what are the effects of a jacketed autoclave

A

both pressure and temperature controlled

air can lead to superheating

56
Q

what is the effect of layering

A

density of air must be twice as dense as steam
air forms layer in any container in an upright position
air will be cooler
container must be at an angle so air can flow out

57
Q

what is dry heat sterilisation

A

inactivation is principally by oxidation
oxidation is less effective than hydrolysis in inactivating bacterial spores - required higher temps for longer
smaller margin for error

58
Q

what are the requirements for dry heat sterilisation

A

temp 150-180
30mins-2hrs
higher temps needed for pyrogen destruction

59
Q

what are the requirements for instruments used in dry heat sterilisation

A

raise temp quickly
even distribution of heat
maintains temp within 5degrees

60
Q

what are dry heat steriliser tunnels

A

heated by infrared irradiation or forced convection in laminal flow tunnels
items sterilised on conveyor belt
shorter processing times
used mainly for glasswear

61
Q

what is dry heat sterilisation used for

A

substances that cannot be subject to moisture, materials that are not penetrated by steam, glasswear, metal surgical items

62
Q

what are some disadvantages of dry heat sterilisation

A

may take longer, temp must be higher, some objects oxidise at higher temperatures

63
Q

when is sterilisation by gases used

A

for temperature sensitive materials; plastics, devices with electronics

64
Q

what gases are used in gas sterilisation

A

ethylene oxide, formaldehyde

65
Q

what are some advantages of gas sterilisation

A

good alternative for materials sensitive to heat/radiation

some processes work at RT

66
Q

what are some disadvantages of gas sterilisation

A

slow, toxic, the gas may be absorbed so require more input

67
Q

what is ethylene oxide

A

used for gas sterilisation, colourless liquid, contact toxicity, readily absorbed by fabrics and plastics, highly flammable

68
Q

what are some advantages of using ethylene oxide

A

broad spectrum, non-selective, bactericidal, can act at room temp

69
Q

what are some disadvantages of ethylene oxide

A

expensive, difficult, potentially toxic, need to be stored safely while gas leaches out and disperses

70
Q

what is fomaldehyde

A

used in gas sterilisation, low bp, aqueous solution used as disinfectant, gas obtained by heating with steam to low-temp-steam fomaldehyde, not flammable

71
Q

how is fomaldehyde used

A

low temp steam-fomaldehyde
operates with sub-atmospheric pressure steam, air removed and steam admitted to heat load, formaldehyde released with steam flushing after sterilisation

72
Q

what are some advantages of using fomaldehyde

A

broad spectrum, non-selective, bactericidal, non-flammable or explosive

73
Q

what are some disadvantages to using fomaldehyde

A

toxic, low penetration power, slow acting, may leve residue of polymers, need to store products after sterilisation while gas leaches out

74
Q

what is the most common source of radiation for sterilisation

A

gamma rays

75
Q

how does radiation sterilisation work

A

mainly targets DNA, direct damage through ionisation or indirect through radiolysis of water
resistance decreases with presence of moisture or dissolved oxygen; most vegetative cells are sensitive to radiation; bacterial spores and viruses are most resistant

76
Q

what do gamma ray radiation sterilisers look like

A

held as pellets packed into metal rods

required reinforced concrete building and stored underwater when not in use

77
Q

what is filtration

A

sterilisation, removal of bacteria/fungi, includes clarification
only for liquids or gases/air

78
Q

what is clarification

A

removal of particulates that would be hazardous if injected

79
Q

what happens during filtration

A

cold process so good for heat sensitive products, fast, aseptic, not absolute so some growth may occur

80
Q

what mechanisms are involved in filtration

A

sieving, adsorption, trapping in filter matrix #9depth filter), low holding capacity(screen filter)

81
Q

what is dead end filtration

A

fast, but filter ‘cake’ builds up and requires cleaning or replacement

82
Q

what is crossflow filtration

A

slower but self-cleaning

83
Q

what materials are used in filtration

A

polyether sulfone, cellulose acetate, nylon, PTFE

84
Q

what is the advantage of using polyether sulfone for filtration

A

wide pH range, low protein absorption

85
Q

what is the advantage of using cellulose acetate for filtration

A

thermal stability, low adsorption

86
Q

what is the advantage of using nylon in filtration

A

resistant to solvents and alkaline solutions

high, non-specific binding

87
Q

what is the advantage of using PTFE in filtration

A

hydrophobic so used for gas/air

useful at high temps

88
Q

what is breakthrough in filtration

A

some microbes or particles pass through depth filters

raw materials with low bioburden or multiple filters can be used to overcome this problem

89
Q

what is growthrough in filtration

A

bacteria and grow and divide through a filter if left there for too long
limiting time of filtration process can prevent this

90
Q

what is high intensity light

A

new method of sterilisation
pulse with 10^5 times intensity of sunlight, UV, used for water or injectables
liquid and container must be UV transarent

91
Q

what is low temperature plasma

A

new technology for sterilisation
gas subjected to electrical field, generates ionised molecules
mainly for medical devices as not suitable for liquids or powders

92
Q

what are some non-viable contaminants

A

particulates, microbial products

93
Q

what are some viable contaminants

A

bacteria, fungi, viruses

94
Q

what causes spoilage in aspirin mixture

A

hydrolysis by acinetobacter

95
Q

what causes spoilage in atropine eye drops

A

atropine loss by pseudonomas

96
Q

what causes spoilage in prednisolone tablets

A

steroid transformed by cladosporium

97
Q

what are some sources of contamination

A

air, raw materials, packaging, equipment, premesis, people

98
Q

what are some common microbes in air

A

spore formers (bacillus, clostridium), non-spore formers (stapholycoccus, streptococcus), moulds (penicillium), yeasts

99
Q

what are some common contaminants in water

A

gram negatives: pseudonomas, e.coli

gram positives: micrococcus, bacillus

100
Q

what are water storage and distribution systems used for

A

maintain water at 80degreesC, circulate water at positive pressure, decrease pipeline, include sterilisation system

101
Q

how is water treated

A

chemicals, filtration, UV light

102
Q

what is the presence of microbes in raw materials

A

high levels of microflora, ensures microbiological quality, consider sterilisation

103
Q

what is the microbe contents of synthetic raw materials

A

low levels of microflora

stored at low moisture content; liquids stored at constant temp

104
Q

how are sterilisation processes validated

A

ca;ibration of equipment, testing quantity of steam, leak tests, software testing, physical/chemical/biological indicators, documentation

105
Q

how is the environment controlled in a manufacturing area

A

air; settle plates and air samplers

surfaces; contact plates, swabbing

106
Q

what are physical indicators of contamination

A

heat sterilisation- digital record of temp, taken at coolest part of loaded steriliser
gaseous sterilisation- leak tests, pressure testing
radiation- plastic dosimeter that darkens in proportion to radiation
filtration- bubble point pressure test

107
Q

what are chemical indicators for sterilisation

A

undergo melting or changing colour

does not correspond to microbiological sterility

108
Q

what are Browne’s tubes

A

acid is produced upon heating, indicator changes colour, speed of reaction determined by colour, different types for dry/moist heat sterilisation

109
Q

what is an Attest biological indicator

A

outer tube, sealed glass ampoule with broth and pH indicator, spore strip inside
after sterilisation, inner ampoule is crushed and tube incubated at 55degreesC

110
Q

what is a sterility test

A

only recognises organisms that grow under conditions of test, sample size is restricted, sampling itself may introduce contamination, all samples in batch must be treated similarly

111
Q

what does a sterility test indicate

A

passing sterility test does not mean batch is sterile, sterility test indicates gross failure, used as additional check, not standalone

112
Q

what is parametric release

A

system of release that gives the assurance that product is of the intended quality, based on process data collected during manufacturing instead of sterility testing
all parameters must be accurately controlled and measured
parametric release is only applied to products that are technically sterilised in their final container

113
Q

what validation is used in parametric release

A

heat distribution and penetration, bioburden, container, cycle lethality studies
reduces pre-sterilisation bioburden testing of each batch
each cycle includes chemical or biological indicators

114
Q

what conditions are required for pyrogen removal

A

250degreesC, distillation, ultrafiltration, ion-exchange chromatography, alkali or oxidising agent treatment

115
Q

what pyrogen testing occurs

A

rabbit pyrogen testing, limulus amoebocyte lysate test, monocyte activation tests

116
Q

what happens during rabbit pyrogen testing

A

three animals are injected and their temperature is recorded over three hours
if individual temp increases of one rabbit then the product fails

117
Q

what are the disadvantages of rabbit pyrogen testing

A

not very sensitive, depends on gender/age of rabbit, repeated animal testing can lead to endotoxin tolerance, low reactivity to endotoxin from certain bacteria, some drugs may influence body temp, not quantative

118
Q

what is limulus amoebocyte lysate

A

blood cells isolated from horseshoe crabs and cells lysed in water, lysate purified (enzymes inactivated by endotoxins)
if mixed with endotoxins, coagulation is observed
more sensitive than RPT

119
Q

what are the disadvantages of limulus amoebocyte lysate testing

A

detects only LPS, some compounds may interfere with clotting system, can only be used if product has p6-8
can now use protein from horseshoe crabs produced by recombinant DNA technology

120
Q

what is a monocyte activation test

A

predicts human response to pyrogens, monocytes (from whole blood or cell line) mixed with sample, measures formation of cytokine IL-1beta

Infection & Immunity (22 decks)

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