Sterilisation Flashcards
What does SAL stand for and what is it?
Sterility assurance level, it’s a probability of how much contamination in a batch
What does PNSU stand for?
Probability of a non sterile unit
What’s the definition of sterile?
Free from all viable forms of life BUT negative state is hard to prove, can we detect all viable forms, sterilisation process not effective for all organisms.
Sterilisation proceeds like a what order reaction?
First order
What two disadvantages of a long sterilisation process?
1) drug may degrade
2) expensive
What’s the minimum required standard for most pharmaceutical products?
PNSU of 1 in 10^6
Why do fungi form spores?
Reproduction
Why do bacteria form spores?
For survival
Which type of bacteria has a thin layer of peptidoglycan?
Gram negative
Which type of bacteria have teichoic and lipteichoic acids?
Gram positive
Which type of bacteria has so membranes and LPS
Gram negative
Sporulation occurs during which phase?
Stationary phase
Do fungi make peptidoglycan?
NO
Name 5 different types of water in industry
1) potable mains water
2) softened water
3) de-ionised water
4) distilled water
5) reverse osmosis
List 3 ways to treat water
1) chemical: hypochlorite + chlorine has
2) filtration
3) UV-light
What’s the D-Value
The time taken to achieve 1 log (90%) reduction in no.viable cells e.g D121 = time at 121degrees C it takes to give 1 log reduction in surviving fraction
The higher the D value the what the resistance
Greater
What’s the Z value?
The temp change required to give a 10 fold change in the D value
Name 3 high level disinfectants
1) aldehydes
2) hypochlorites
3) peroxydens
Name 5 intermediate disinfectants
1) alcohols
2) biguanides
3) ioddine/iodophore
4) phenolics
5) QACs
Name one low level disinfectant
Phenolics
What two environmental factors affect choice of disinfectant?
1) organic matter- blood eg can decrease antimicrobial capacity
2) divalent cations- block disinfectant adsorption sites
What’s the temperature coefficient
Q10
Name the process of the suspension test
1) dilutions of disinfectant added to standardised bacterial suspension in water + albumin at set temp
2) remove sample
3) neutralise disinfectant
4) determine viable count
What don’t alcohol gels kill?
C.diff spores or noravirus
Name two most likely contaminants of eye products
1) pseudomonas aeruginosa
2) staphylococcus aureus
Name 2 organic acids used as agents
Benzoic acid
Sorbic acid
What do you need to consider with organic acid and esters as agents?
pKa
Name an organic ester used as an agent
P-hydroxybenzoic acid
At what percent are alcohol agents bactericidal
> 50%
Are aliphatic alcohol agents sporicidal?
NO
Name 3 aromatic alcohols used as agents
Benzyl alcohol
Phenylethanol
Phenoxyethanol
Name three classes of alcohols used as agents
Aliphatic
Aromatic
Substituted
What’s the disadvantage of chlorbutol and bronopol (substituted alcohols) as agents
Unstable and not sporicidal
Name 3 disadvantages of aldehydes used as agents
Activity decreased by polymerisation
Toxic
Carcinogenic
Name the more active aldehyde agent and it’s concentration
OPA- ortho-phthalaldehyde 0.5%
What’s the disadvantage of biguanides as agents
Activity decreased by anionic compounds e.g soups, and also by organic matter
What do you have to do with the halogen agents hypochlorites daily?
Dilute to in-use conc due to instability
Name 3 types of phenolic tar acids
Cresol
Xylenols
Ethyl phenols
Name 3 ways antimicrobials can affect the cell wall
1) breakdown cell wall
2) affect integrity of outer membrane
3) X-link cell wall
Name a powerful oxidative agent for destruction that undergoes chemical oxidation
Chromic acid
Name three types of sterilisation processes
Destruction
Killing/inactivation
Removal
Name 5 sterilisation processes in the European pharmacopoeia
1) steam sterilisation
2) dry heat
3) ionising radiation
4) gaseous sterilisation
5) filtration
Moist heat sterilisation involves what temperature
121-134
Name 2 products used in gaseous sterilisation
Ethylene oxide or formaldehyde
Dry heat sterilisation uses what temp?
160-180
Sterilisation processes have a compromise between what two things
Good antimicrobials activity and product stability
What’s an autoclave
Like a pressure cooking but more than 100 degrees, high pressure, organisms killed by temp, hydration and time
What is superheated steam?
Is water in the vapour phase and behaves like a gas, decrease temp decrease pressure
What is supersaturated steam
Also known as wet steam, is in liquid phase and is made up of small droplets of water held in suspension by convection currents
What is dry saturated steam?
Exists only on the phase boundary, if you lower the temp it will condense
Name three types of steam
Superheated steam
Supersaturated steam
Dry saturated steam
What type of steam is suitable for sterilisation
Dry saturated steam
Name three ways in which dry saturated steam works in sterilisation
Heat
Hydration
Penetration
What is sensible heat
As it’s released it results in a change of temp
What is latent heat?
As released results in change of state not temp e.g ice to liquid
Why is dry saturable steam more penetrable than superheated steam?
Upon condensation volume contracts >800 times this creates a local vacuum drawing in more steam
Name two large scale autoclave sterilisers
Gravity displacement autoclave
Porous load autoclave (vacuum assisted)
What is necessary on a large scale autoclave in order to maintain even heat distribution?
Heated outer jacket
Is a porous load vacuum assisted?
YEH MAN
Name the three stages if operation for large scale porous load autoclaving
1) air removal and steam admission
2) heating up and exposure
3) drying and cooling
There’s two main problems with autoclaving what are they
Air in autoclave
Superheated steam
Using dry heat sterilisation, inactivation is principally by what
Oxidation
What does LTSF stand for
Low temp steam formaldehyde- 37% aqueous solution formalin with steam
In formaldehyde gas sterilisation how is the formaldehyde released
By vaporisation from formalin
What temp and gas is required in formaldehyde gas sterilisation
Temp 70-75degrees
Gas 15-100mg/l
Name four types of radiation sterilisation
Gamma rays
Electron beams
X rays
Uv light
Dose of radiation specified by BP is what
25kGy
Name 4 materials used for filtration
Polyether sulfone (PES)
Cellulose acetate (CA)
Nylon
Polytetrafluorethylene (PTFE)
What does the BP limit the filtration time to and why
4hours due to bacteria dividing and growing on filter
What is a biological indicator usually used for
Validating method not as a routine control indicator
Explain the process of a attest biological indicator
After sterilisation, inner ampoules is crushed and tube inoculated at 55degrees
Fail= yellow
Pass= purple
Name three pyrogens tests
Rabbit pyrogen tests (RPT)
Limulus amoebicyte lysate (LAL)
Monocyte activation tests (MAT)
Name a physical indicator for testing filtration
Bubble point pressure test
Name a physical indicator for radiation
Plastic dosimeter darkens in proportion to radiation
Name a physical indicator to test gas sterilisation
Leak tests, pressure testing
Name the three ways autoclaves kill organisms
Temperature
Hydration
Time
Name three factors playing a role in why dry saturated steam is used in sterilisation
Heat
Hydration
Penetration
What is sensible heat
When exchanged = change of temp
What is latent heat
When exchanged results in change of state NOT TEMP
Supersaturated steam releases what type of heat?
Has no latent heat will release only sensible
What type of heat does superheated steam release?
Has both sensible and latent heat but in absence of condensation will release only sensible heat
What type of heat does dry saturated steam release?
Both sensible and latent
Can bench autoclaves suffer from superheating?
No cos there’s water in the vessel itself, increase temp more steam is produced both temp and pressure increase so steam remains in boundary phase #nobiggy
Name two large scale autoclaves
Gravity displacement autoclave
Porous load autoclave (vacuum assisted)
Is a porous load autoclave vacuum assisted?
You betcha
What does a large scale autoclaves have that bench don’t?
Separate external/internal steam generator
Which have shorter cycle times bench or large scale autoclaves and why
Large scale cos the steam is available immediately due to separate steam generator
Do large scale autoclaves wear clothes
Yh heated outer jacket ?
In large scale autoclaving how do you prevent bursting of products
Air ballasting, to prevent layering of this maintained air you may require a fan or spraying mechanism
How does dry heat sterilisation work
Oxidation
Name two instruments that can be used for dry heat sterilisation
Hot air oven
Dry heat steriliser tunnel
What are the 3 key disadvantages of dry heat sterilisation
Long time to heat up
Temp must be higher and longer
Large temp variations in load
What are 3 disadvantages of gas sterilisation
Slow
Toxic
Gas may be absorbed
What’s the boiling point of ethylene oxide?
11 degree C
Ethylene oxide sterilisation a required carefully controlled humidity .. Why?
Cos organisms in dried state are more resistant
What should you do with products sterilised by gaseous sterilisation after?
On open shelf for days
In forced aeration cabinet (2-24hrs)
What are the two types of mechanisms for filtration
Dead end filtration
Cross flow filtration
Two disadvantages of filtration
Grow through
Breakthrough
Quality control involves what
Testing of final product
Quality assurance involves what
Assure that all stages of manufacturing processes contribute to the quality of the end product
Name three types of validation and control
Environmental control
Control of sterilisation process
Control of the final product
What does GMP stand for?
Good manufacturing practice (orange book)
In a clean room what type of air filter is used
HEPA
Are sinks allowed in grade A/B area?
No no
What two pieces of equipment do you have in a grade A clean room
Laminar flow cabinets
Isolator
What’s a benefit of a laminar flow cabinet
Repetitive strain injury less likely
When would you use vertical laminar flow cabinets over horizontal
When dealing with hazardous substances ????
Where would you ? vertical laminar flow cabinets
In a separate room away from any draughts, grade B
Name two types of flow in laminar flow cabinets
Horizontal
Vertical
Name two types of flow in isolators
Turbulent
Unidirectional
Name some benefits of isolators
Cheaper to run
Disturbances in air flow not critical
Better for operator protection (-ve pressure)
Minimum operational parameters
What type of pressure does a type 1 isolator have
Positive
What type of pressure does a type 2 isolator have
Negative
Which type of pressure in an isolator is less prone to leaks
Positive
Name the two types of film you can have in an isolator
Rigid
Flexible
Flexible film is only suitable in what pressure
Positive
What’s a benefit of using flexible film in an isolator
Offers less limited workspace
In sterility testing what type of fluid do you use for anaerobic organisms
Thioglycollate medium
In sterility testing what type of medium do you use for aerobic bacteria and fungi
Soya bean casein digest medium
List 5 controls in sterility testing
Test media for sterility Test media for nutritive support Validation test (neutralise anti microbe) Environmental monitoring Operator technique test
List 5 modes of action of agents
Cell wall Cell membrane Cytoplasm Nucleoid Ribosomes
Name the two types of resistance
Intrinsic/innate
Extrinsic/acquired (phenotypic or genotypic)
List 3 ways biofilms are such a problem
Resistant to antibiotics
Resistant to biocides
Difficult to phagocytose by immune
What are the main type of bacteria that form spores
Gram positive
What do fungi look like
Eukaryotes, cell wall containing polymeric sugars
Name 3 types of fungi
Yeast
Multicellular filamentous moulds
Macroscopic filamentous fungi
How do moulds grow
Masses of overlapping and interlinking hyphal filaments
Are yeasts single cells?
SHYEH
What are Protozoa
Diverse group of single celled animal like eukaryotes
Do Protozoa have cell walls
No no boi
Do Protozoa survive drying well?
No cos no cell wall unless in form of cysts
What 2 things can infection from prions lead to
CJD
BSE
