Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Management of Infection > Lecture 18 - Sterilisation Techniques > Flashcards

Lecture 18 - Sterilisation Techniques Flashcards

1
Q

What do medical or surgical procedures often breach?

A

the protective barriers of the host e.g. skin and mucosal surfaces or are topically applied to important body structures e.g. eyes, ears

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why is it critical that the pharmaceutical or surgical products being used are sterile?

A

to prevent the exposure of host tissue to potentially harmful microorganisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Examples of pharmaceutical sterile products?

A

parenteral injections & infusions, ophthalmic preparations, ear preparations, wound and bladder irrigations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Examples of sterile surgical products?

A

wound dressings, artificial joints, cardiac pacemakers, surgical instruments, surgical gloves, hypodermic needles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the concept of sterility from an academic perspective?

A

complete absence of viable microorganisms from a product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is sterility from a Pharmacopoeial perspective?

A

the tests to establish sterility are often limited due to the grounds of statistical probability due to limitations in the testing criteria available

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is sterilisation?

A

the process of removing or killing microorganisms from the product to render it sterile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are examples of sterilisation methods?

A

heat (steam & dry heat)

radiation (g-rays or high energy electrons)

gaseous (ethylene oxide or formaldehyde)

filtration (with subsequent aseptic processing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does the sterilisation method applied depend on?

A

the physiochemical stability of the product to be sterilised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the most common type of sterilisation used?

A

steam sterilisation, accounts for 80% of sterilisation applied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does sterility depend on?

A

microbial burdens of raw materials, equipment and facility

the operators

the use of validated sterilisation protocols

in process control of the process and the production environment

suitable storage conditions of the finished products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is storage of the finished product important?

A

to prevent recontamination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What should parenteral products be?

A

be pratically free from particles

be pyrogen free

be physiological compatible in terms of pH, tonicity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What should eye drops be?

A

buffered near physiological pH of tears

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What do particles do if they are entered into a patient?

A

they have the ability to block capillary beds or travel somewhere more distance and block an important capillary bed, leading to reduced oxygen flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What might pyrogens cause?

A

unwanted side effects e.g. pyrexia or disturb blood pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the heat sterilisation methods?

A

moist heat and dry heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does moist heat denature?

A

cell wall and cytoplasmic constituents and/or hydrolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does dry heat denature?

A

denatures by oxidation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the destruction action of heat on microorganisms?

A

most pronounced in the presence of moisture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does the enhanced sensitivity of microorganisms to heat in the presence of moisture cause?

A

reduced operating temperatures and times to effect sterilisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Time and temperature of moist heat sterilisation?

A

115-118 degrees C 69kPa = 30mind

121-124, 103kPa = 15 mins

126-129, 138kPa = 10 mins

134-138, 209kPa = 3 mins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Time and temperature of dry heat sterilisation?

A

160 degrees C = 120 mins

170 degrees C = 60 mins

180 degrees C = 30 mins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

At normal atmospheric pressure steam kills?

A

most but not all types of microorganisms

bacterial spores remain viable even if they are heated for prolonged periods of time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are higher steam temperatures used for?

A

to ensure that all microorganisms are killed in a product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How do we obtain higher steam temperatures?

A

the water must be heated under pressure in an autoclave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is steam?

A

water in the vapour (gas) phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is needed to transform water from the liquid to the vapour state?

A

energy must be added to the liquid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How can the energy bringing about this change be subdivided?

A

energy to raise the temp of the mass of liquid water to its boiling point

energy to transform the mass of liquid water at its boiling point to a vapour pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the energy to raise the mass of liquid to boiling point?

A

4.2kJ/kg/degrees C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the latent heat of vaporisation?

A

the energy to transform the liquid at its boiling point to a vapour pressure

2220kJ/kg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the exact boiling point of water determined by?

A

the pressure of the atmosphere in which the water is being heated (boiling point will increase with increasing pressure)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the boiling point of water at atmospheric pressure?

A

100 degrees C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

When is steam referred to as being saturated?

A

when it is at a temperature corresponding to the liquid boiling point appropriate to its pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the effectiveness of saturated steam under pressure at destroying organisms related to?

A

the physical properties of the steam under pressure that allow the steam to efficiently transfer heat to the product requiring sterilisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What happens when steam comes into contact with an object whose temperature is below the steams saturation temperature?

A

the steam condenses into liquid water (at 121 degrees C) on the object and transfers the latent heat of vaporisation (2220kJ/kg) to the object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What does the condensation cause?

A

a rapid contraction in volume (~785x decrease) and creates a localised region of low pressure that is filled by additional saturated steam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What does this contraction in volume ensure?

A

the rapid penetration of the load by the steam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

When does this process continue until?

A

the object reaches the temperature surrounding the steam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

When are increased pressures used?

A

only to elevate the temperature at which saturated steam is produced

the pressure itself has no antimicrobial action

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Why is water quality used to produce saturated steam important?

A

contamination with chemical residues within water is possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What does purity of the water effect?

A

the temp it can achieve at a particular pressure

chemicals in water can contaminate the product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What is superheated steam?

A

when the temperature increases above the saturation-pressure boundary or if the pressure is reduced below the saturation temperature-pressure boundary then the steam is referred to as being super heated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

How does superheated steam behave?

A

like an ideal gal and is not as lethal to microorganisms as saturated steam?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What does superheated steam cause?

A

do not get transfer of latent heat of vaporisation and do not get lethal kill of microorganisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What happens if you get a reduction of temperature at fixed pressure?

A

you get a puddle of water which means there is no transfer of latent heat of vaporisation, not as much antimicrobial action

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What are the thermal stages within an autoclave?

A

A (rising) - heating up phase

B (flat) - holding phase, where most of microbial killing happens

C (descending) - cooling down phase

48
Q

What products are sterilised by moist heat sterilisation?

A

only products that can withstand the process temperatures and that are not susceptible to moisture damage can

49
Q

3 categories of products sterilised by moist heat?

A

aqueous products

non-pourous loads

porous loads

50
Q

Examples of aqueous products sterilised by moist heat?

A

ophthalmic products

large/small volume parenterals

51
Q

What are aqueous products normally contained in?

A

a non-porous container made of glass or thermostable plastic

52
Q

Why does the saturated steam not have to come into direct contact with the product?

A

the water content in the product will itself ensure inactivation of microorganisms as long as it is maintained at the sterilisation temperature

53
Q

How are products in containers sterilised?

A

the steam condenses onto the surface of the container and there is a massive transfer of the latent hear which is transferred inside the container, warm up through convection processes and sterilises the products

54
Q

What non-porous products are sterilised using moist heat?

A

surgical instruments, rubber closures for vials or items used in the production of sterile products e.g. rubber tubing for transfer of sterile solutions or stainless steel mixing blades

55
Q

What are non-porous loads usually wrapped in?

A

special containers that allow the penetration of saturated steam during the sterilisation process and prevent the ingress of microorganisms after the sterilisation process is complete

56
Q

What are porous loads that would be sterilised?

A

wound dressings and filters

57
Q

For porous loads what is done after sterilisation?

A

there will be a vacuum to pull of any residual moist steam present on the product so it is not soggy

58
Q

What does the paper do for non-porous loads?

A

prevents introduction of any new microorganisms onto the product once it has been taken out of the autoclave

59
Q

Where is dry heat sterilisation performed in?

A

a hot air oven

poor heat transfer capacity of air lead to prolonged sterilisation cycles at higher temperatures than moist heat

60
Q

What is heat provided by in dry heat sterilisation?

A

electrical heating elements placed around the internal insulated chamber wall

61
Q

What do fans in the oven do?

A

ensure that air is evenly distributed throughout the oven to prevent temperature gradients within the oven

62
Q

How is heat transferred to products in dry heat sterilisation?

A

by conduction, convection and radiation

63
Q

What can influence heat transfer and the performance of the oven?

A

size and distribution of the load

64
Q

Why is dry heat sterilisation insufficient?

A

there is transfer from air onto the product so it takes a lot longer than moist heat

65
Q

What is dry heat sterilisation used to sterilise?

A

a variety of thermostable products that are moisture sensitive

ophthalmic ointments
oil, wax, fat excipients that are used in the manufacture of depot injections, implants or ointments

66
Q

What else is dry heat used to sterilise>

A

powders used in the manufacture of sterile suspensions or powders

depyrogenation of glassware

67
Q

What temperatures are routinely used in dry heat sterilisation?

A

> 200 degrees C

this destroys bacterial endotoxins on glassware

68
Q

What does the BP require for endotoxin?

A

3-log10 reduction in endotoxin

69
Q

How is depyrogenation of glassware done?

A

putting it through a heated tunnel of >220 degrees C, by the time it comes out all of the toxins have been chemically denatures

70
Q

What is used in radiation sterilisation?

A

only high energy gamma rays and high energy electron beams

71
Q

When did the introduction of radiation sterilisation become widespread?

A

after the development of the nuclear industry

72
Q

What did the development of the nuclear industry allow?

A

the main isotope Co-60 to become available in sufficient quantities

73
Q

What does Co-60 do?

A

decays in a single step process to produce Ni-60

Co-60 -> Ni-60 + 2g-rays + b

74
Q

What is the total energy of the gamma rays and electron released from Co-60?

A

2.81Mev, which is 4.4x10-13J

75
Q

What does the energies of the two rays allow?

A

them to penetrate through most products

penetrate into a product with a density of water to a depth of 30cm

76
Q

What does the BP recommend a dose received to achieve terminal sterilisation?

A

a dose of 25kGy (2.5x10^4 J/kg)

77
Q

What is the energy from the gamma rays?

A

small compared to the energy input provided by moist heat or dry heat methods of sterilisation

78
Q

Why is the energy delivered by an individual gamma ray highly localised?

A

it penetrates through the product

79
Q

What does the gamma ray have sufficient energy to do?

A

break covalent bonds found between atoms in organic molecules

80
Q

What is a carbon to carbon bond broken by?

A

an energy input of 5.77 x10^-19 J

81
Q

What is the alteration in the chemical composition of important macromolecules induced by?

A

the gamma rays results in the death of the microorganisms (may also denature product)

82
Q

What is gamma radiation used for?

A

the sterilisation of medical devices such as prosthetics, catheters, disposable plastic syringes and surgical clothing

83
Q

What else has gamma radiation been used as ?

A

a cold sterilisation process for heat sensitive pharmaceuticals such as monoclonal antibodies, enzymes and peptides in addition to certain product containers

84
Q

What chemicals have been used as gaseous sterilants?

A

ethylene oxide

formaldehyde

peracetic acid

hydrogen peroxide

85
Q

What are the majority of gaseous sterilisation operations performed using?

A

ethylene oxide

86
Q

What is ethylene oxide?

A

a colourless, practically odourless cyclic ether with a boiling point of 10.7 degrees C at atmospheric pressure

87
Q

What is ethylene oxide in its pure form?

A

explosive and highly flammable with air

88
Q

What is done to reduce the risk of explosion of ethylene oxide?

A

it is commonly mixed with an inert gas such as carbon dioxide or dichlorordifluoromethane

89
Q

What does ethylene oxide do?

A

chemically alkylates a range of chemical functional groups present within the microorganisms

90
Q

What impact upon effectiveness of sterilisation cycle?

A

gas concentration (500-800mg/L)

process temperature (40-60 degrees C, typically 55-60)

RH (40-80%, most important parameter)

91
Q

What are the typical process times of gaseous sterilisation?

A

between 3 - 36 hours

92
Q

What is ethylene oxide used to sterilise?

A

wound dressings, prothesis and intravenous sets

93
Q

What can ethylene oxide not sterilise?

A

aqueous solutions or gas impermeable products

94
Q

When should ethylene oxide sterilisation be used?

A

when other methods are not available or applicable

it is less reliable than other sterilisation methods

95
Q

What is filtration?

A

the separation of an insoluble solid from a liquid or gas by means of a porous medium (filter) that retains the solid but allows the passage of liquid or gas

96
Q

When does filtration result in a sterile liquid or gas?

A

when the insoluble material is a microorganism suspended either in a liquid or gas and is removed by filtration

97
Q

Why is sterilisation by filtration not a terminal process?

A

the resulting sterile solution obtained must be filled and sealed into its final container without re-introduction of microorganisms

98
Q

How can contamination prevented?

A

further processing of the sterile filtrate must be carefully performed under aseptic conditions

99
Q

what does aspetic processing require?

A

greater manipulations and is more sensitive to the environmental conditions and depended on the capabilities of the operators

100
Q

What type of sterilisation method should always be chosen?

A

a terminal sterilisation method when possible

101
Q

What are modern filters made of?

A 
polymers such as 
cellulose esters (acetate and nitrate)

PTFE

nylon

polysulfone

102
Q

What does polymer selection depend on?

A

process conditions e.g. pH, presence of organic solvents, salts

103
Q

What is retention?

A

capture particles that are too large to fit through the membrane apertures (holes or channels)

104
Q

What is inertial impaction?

A

particle momentum leads to it embedding/lodging into membrane crevices and dead-ends

105
Q

What is adsorptive sequestration?

A

ionic or hydrophobic interactions between particles and membrane polymer

106
Q

What is adsorptive sequestration dependent on?

A

chemistry and process conditions (e.g. pH, salts, solvents)

107
Q

Wha is the nominal pore size of sterilising grade filters?

A

0.2um

108
Q

What does the pore size still allow?

A

passage of certain types of microorganism or metabolites/macromolecules through

109
Q

Examples of things that can fit through pore size?

A

viruses (20-300nm)

mycoplasma (200-300nm)
endotoxin (~10^-10m)

110
Q

What does the BP qualify filter performance in terms on?

A

microbial retention due to the absolute pore size distribution

111
Q

What does the BP state a sterilising filter must retain?

A

a challenge of 10^7 CFU of brevundimonas diminuta per cm2 of filter

112
Q

Why must you qualify every membrane with your product before using to filter sterilise product?

A

no reference is made to the test conditions under which the filter is challenged

113
Q

What is filtration primarily used for?

A

to sterilise solutions that cannot withstand head treatment

114
Q

What else is filter sterilisation used for?

A

to sterilise gases used in other processes e.g. dry heat sterilisation using hot air

115
Q

What is filtration commonly used to filter?

A

solutions that are undergoing terminal sterilisation to enhance the microbial quality assurance further

Management of Infection (36 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions