sterilisation Flashcards
what are the different types of sterilisation methods
dry heat
moist heat autoclave, gravity steriliser
aseptic filtration
gamma irradiation
chemical sterilisation (ethylene oxide/ nitrous oxide, h2o2 fog)
lyophilisation
what are the specifications, advantages and disadvantages of dry heat sterilisation method
specs: 180degC for 30min, 170degC for 1h, 160degC for 2h
advantages: destroys pyrogens
disadvantages: heat sensitivity
what are the specifications, advantages and disadvantages of moist heat autoclave sterilisation method
specs: 121degC for 15mins
advantages: biological indicator to verify sufficient heat/ pressure
disadvantages: heat/ moisture sensitivity
what are the specifications, advantages and disadvantages of aseptic filtration sterilisation method
specs: numerous fiber/ size load specs
advantages: filter integrity test to verify filter did not rupture
disadvantages: filter must be certified for volume and filtrate load
what are the specifications, advantages and disadvantages of gamma irradiation sterilisation method
specs: requires very high radiation to be effective
advantages: containers and packaging may still be intact
disadvantages: not good for some heat sensitive
what are the specifications, advantages and disadvantages of chemical sterilisation method
specs: depending on gas used - different saturation and permeation
advantage: less invasive, good for heat sensitive
disadvantage: compatibility issues, require tight wrap to avoid leaks, contaminates adjacent areas
what are the specifications, advantages and disadvantages of lyophilisation sterilisation method
specs: multi step process
advantage: ease of processing a liquid, stability
disadvantage: expensive, requires sterile diluent
what is meant by aseptic process simulation
method of validating an aseptic process using a microbiological growth medium as substitute for product and employing method that closely approximate those used during the drug product process
what are the two types of aseptic process simulation
FDA and EU
what is the process of the FDA aseptic process simulation
validated using microbiological growth medium in place of product
includes exposing microbiological growth medium to product contact surfaces of equipment, container systems, critical environments and process manipulations in order to closely simulate same exposure
what is the process of the EU aseptic process simulation
validated using nutrient medium
imitate as closely as possible the routine aseptic manufacturing process and include all critical subsequent manufacturing steps, should also take into account various interventions known to occur during normal production as well as worst case scenarios
what is the importance of APS and its disadvantages
importance of APS:
1. fundamental to validate the aseptic process globally
2. important to assess machine assembly, standard interventions, handling and storage of components, surrounding environment, number of personnel and their activities, length of production
3. useful to understand process and define routine procedures
4. powerful or weak depending on its design and interpretation of results
disadvantages:
1. not enough to evaluate whole process as it is a point in time
2. not a QA method and thus need full validation of all sub processes
3. need risk assessment and worst case scenarios for evaluation
what are the characteristics of aseptic filtration
performed using a 0.22microm filter, applied to thermolable objects, can be used to remove pyrogens, process of removing microorganisms from fluid stream without adversely affecting product, at min. conc of 10^7 CFU/cm2
what is the difference between microfiltration, ultrafiltration, nanofiltration, reverse osmosis
microfiltration: 0.1-1.0microm pore, 0.1-5bar pressure, virus, multi and divalent ions and water pass through
ultrafiltration: 0.01 to 1.0microm pore, 0.1-5bar pressure, multi and divalent ions and water pass through
nanofiltration: 0.001 to 0.1microm pore, 8-40bar pressure, some multi valent, divalent ions and water pass through
reverse osmosis: 0.001microm, 30-85bar pressure, only water pass through
what is meant by the term lyophilisation
freeze drying, process in which water is removed from a product after it is frozen and placed under a vacuum, allowing the ice to change from solid to vapor without passing through a liquid phase
what are the steps in lyophilisation sterilisation process
- dissolve drug and excipients in a suitable solvent, generally water for injection (may need buffer to change pH)
- sterilise bulk solution by passing it through a 0.22microm bacteria retentive filter
- fill into individual sterile containers and partially stoppering the containers under aseptic conditions
- transport partially stoppering containers to lyophiliser and load into chamber under aseptic conditions
- freeze the solution by placing the partially stoppered containers into freeze drying chamber or prefeezing in another chamber
- apply vacuum and heat the shelves in order to evaporate water from frozen state
- complete stoppering of vials usually by hydraulic or screw rod stoppering mechanism installed in lyophilisers
why are containers in lyophilisation process partially stoppered
to decr amount of air going in and out and decr the amount of possible contamination
why are containers in lyophilisation process stoppered in low humidity
to maintain stability of product
what are the main stages in the lyophilisation process
freezing, primary drying (sublimation), secondary drying (desorption)
what are the considerations in each of the main stages of the lyophilisation process
freezing: quick freezing of a small volume, crystal size may affect final product, speed of this process can change crystallinity of compound, some substances may have polymorphism (two different crystal sizes that behave differently), if not cold enough may still have water inside
primary drying (sublimation): drying under vacuum, endpoint is when temp starts rising (temp will be stable then start incr which is point where it is starting to heat product), if not hot enough sublimation may not occur thus there will still be water in product
secondary drying (desorption): under vacuum, endpoint is when water content <1%
what is the process of aseptic simulation for liquids
compounding/ solution preparation
1. buffer used instead of final product
2. buffer sterilised
3. buffer come into contact with all surfaces involved in process
4. routine test like filter functionality assessment, holding time, sampling
filling:
1. container, caps and equipment must be cleaned and sterilised
2. buffer should come into contact with whole container and cap through shaking
3. container must be transparent to allow inspection (except photosensitive compounds)
4. size of container must be consistent with product and process
what is the process of aseptic simulation for lyophilisation
filling:
1. filled with buffer and loaded on the lyostat, vacuum applied could be comparable or less than the real one for the same time of the real process
2. lower vacuum and time
what is clean-in-place/ sterilisation-in-place (SIP)
consolidated practice, setup can be performed before sterilisation, long holding times can produce product sticking, product formulation is usually prepared just before filling, batch dimension can be limited by storage tank size
what is the process of aseptic simulation for powders
filling:
1. filling machine can do two consecutive filling (powder and medium or placebo and medium)
2. medium should be enough to dissolve powder
3. possible contamination
filling -> growth and sterilised (using steam, filtration or radiation) -> growth promotion test and sterility verification -> visual inspection
what is the characteristics of the placebo used in aseptic simulation for powders
mechanical properties similar to final product, easy to sterilise (validate method), soluble in medium (lactose, mannitol, PEG, NaCl), no effect on medium in growth promotion test
what is the characteristics of the negative control used in aseptic simulation for powders
medium without placebo
what is the key points of in aseptic simulation for powders
- CIP/SIP not applicable
- dose/QC parts are aseptically assembled
- set up longer than for liquid
- blending usually prepared offline
- batch dimension not limitation
- presence of powder requires interventions for cleaning
- machine turning may require human intervention
what are the corresponding growth mediums for each type of microorganisms
aerobic, fungi, yeast -> soybean casein digest medium or trypticase soy broth
anaerobic -> fluid thioglicollate medium
yeast -> sabouraud dextrose agar
what are the criterias for growth promotion tests
involves inoculation with < 100CFU of test microorganisms/microorganisms of the process environment at 20-25degC or 30-35degC for 72h
visual inspection to spot any contamination/ turbidity which is performed after incubation at 20-35degC for 14d (or at least 7d with two diff temp), at half time and end of incubation period
compare terminal sterility and aseptic processing
terminal sterility
1. use of a lethal treatment on microorganism (heat, radiation, chemical)
2. relatively easy to reproduce and validate
3. not for all materials (packaging and medical devices)
aseptic processing
1. removal or separation of microorganisms
2. high risk of contamination
3. more variables in process and harder to control
4. fewer issues with materials
what are the corresponding sterility testing to different types of pharmaceutical products (filterable, large volume available, medical devices, used materials that might be damaged or impenetrable by moist heat, heat sensitive medical devices and surgical supplies, medical products and packaging materials, water treatment)
- filterable -> membrane filtration sterility test
- large volume available and can take a small sample without affecting final quantity -> direct inoculation sterility testing
- medical devices -> sterility testing for medical devices, moist heat sterilisation
- used materials that might be damaged or impenetrable by moist heat -> dry heat sterilisation
- heat sensitive medical devices or surgical supplies -> chemical sterilisation
- medical products and packaging materials- -> gamma radiation
- water treatment -> ozone
samples are incubated for up to 14d at 32.5 and 22.5degC prior to examination
what are the factors in determining sample size for sterility testing
- number of units in each batch
- volume of liquid per container
- method of sterilisation
- manufacturing requirements of the regulatory
what is the purpose of a minimum sample size
to minimise possibility of a false neg result
what are the corresponding probability of failing based on number of contaminated units in a batch
1 in 1000 -> 2%
5 in 1000 -> 9.5%
1 in 100 -> 18%
5 in 100 -> 63.2%
1 in 10 -> 86.5%
5 in 10 -> 100%
what is the process of membrane filtration sterility testing
passing through 0.45microm membrane filter in a filtration canister -> culture medium -> incubation of filtrate in cultre medium (not 0.22 microm as this is to prepare sample not yet to ensure product is sterile)
what is meant by most probable number (MPN)
statistical method used to estimate the viable numbers of microorganism in a sample by inoculating the broth in 10fold dilutions and is based on principle of extinction dilution
what is the difference between MPN and CFU
MPN estimates the conc of microorganisms in a sample by growing it in a liquid broth while CFU estimates number of viable microorganisms by growing them in a solid agar
what is the process of direct inoculation sterility testing
aseptic removal of a sample -> inoculation in culture medium -> incubation
what are the disadvantages of direct inoculation sterility testing
- low sensitivity due to small volumes of product (in contamination quite low may become undetected -> false neg)
- may need neutralisation if product has antimicrobial properties
- cloudy samples may affect the reading of microbial growth -> reasons not due to microbial growth leading to false pos
what is the process of sterility testing for medical devices
device to be tested is in direct contact with test media throughout incubation period during which any microorganism in or on the device will grow and proliferate
what are the advantages of sterility testing for medical devices
suitable for products with hollow space and pipes (rinsing of solution or flush with growth medium)
what are the considerations for sterility testing of medical devices
done in sterile environment to prevent external contamination, may involve cutting of pipes to ensure growth medium reaches all parts as air may be trapped that prevents reach by growth medium and result in spots that go undetected
what is the process of moist heat sterilisation
direct steam contact at the required temp and pressure for the specified time, moist heat destroys microorganisms by irreversible coagulation and denaturation of enzymes and structural proteins, SAL of 10^-6
what is the purpose of D value in moist heat sterilisation
direct comparison of the heat resistance microorganisms
what are the parameters involved in moist heat sterilisation
steam - ideally dry saturated steam and entrained water (water has better thermal conductivity than air)
pressure - required to achieve high temp
temp - 121 and 132 degC
time - min exposure period depend on material and object
what are the three types of autoclaves for moist heat sterilisation and how do each of them work
- gravity displacement autoclave (let stem in, according to changes in temp and humidity - cold steam at bottom and hot steam at top allows for circulation)
- high speed prevacuum steriliser (vacuum created and let steam in to fill up vacuum space)
- steam flush pressure pulsing process (continuous inlet of steam entering at very high pressure in pulses)
what is meant by F value and what are the relevant equations to take note
F value measures the equivalent time, not clock time, that an monitored article is exposed to the desired temperature
F = time interval between successive temp measurements (change in t) x 10^ (T-T0/Z) where T is product temp and T0 is ref temperature of 121degC for steam sterilisation and Z is temperature increase needed to reduce D value by a factor of 10
Z = T2-T1/ lgD1-lgD2
F0 = change in t x 10^ (T-121/10)
what does 121degC for 15min mean
heat product at that temp for this amount of time, not system
what is the process of dry heat sterilisation
forced air or mechanical convection steriliser is equipped with a motor driven blower that circulates heated air throughout the chamber at a high velocity thus permitting a more rapid transfer of energy from air to instrument
what are the advantages of dry heat sterilisation
- easier to operate and maintain
- slow rate of heat penetration
what are the types of dry heat sterilisers
- static air type
- forced air type
what is the normal temperature used in dry heat sterilisers for glassware
220degC
what is the only sterilisation method that can remove pyrogens
dry heat sterilisation
what are non endotoxin pyrogens
other microbial substances including those derived from gram pos bacteria, viruses, yeasts, fungi
what are non microbial pyrogens
originate from rubber particles, microscopic plastic particles or metal compounds in elastomers
what are the animal based and in vitro testing to test for broad range of pyrogens
animal based: rabbit pyrogen test (RBT)
in vitro: monocyte activation test (MAT)
what are the animal based and in vitro testing to test for endotoxins only
animal based: bacterial endotoxins test (eg. LAL test)
in vitro: recombinant factor C (rFC)
what is the temperature set for chemical sterilisation and what are the common chemicals used
60degC
liquid sterilants used include ethylene oxide, formaldehyde, h2o2, peracetic acid
what are the properties of ethylene oxide (ETO) used in chemical sterilisation
ETO is an alkylating agent, used:
1. pure
2. mixed with CFC/CO2/HCFC
3. in combi with peracetic acid/H2O2, plasma and ozone
residue eliminated via proper aeration (supplying with air)
induces irreversible inactivation of microorganisms but not safe to use
what are the properties of peracetic acid used in chemical sterilisation
highly biocidal oxidiser that maintains its efficacy in presence of organic soil
mostly used for endoscopic tube with activity against bacteria, fungi, yeast
used at 35% in combination with anticorrosive agent like sulfonate (dilute to 0.2% if plastic)
process time around 12 mins
by product is acetic acid and water which are not dangerous
what are the properties of gas plamas like H2O2 plasmas used in chemical sterilisation
gas plasmas are generated in an enclosed chamber under a deep vacuum using radio frequency or microwave energy to excite gas molecules to produce charged particles mostly in the form of free radicals -> deep vacuum used to pull H2O2 of 30-35% from disposable catridge -> vaporised H2O2 carried into sterilisation chamber by a carrier gas like air (neg/pos pressure)
37-44degC for 75min (for temp sensitive products but tradeoff with long time)
wide range of efficacy incl mycobacteria, MRSA, clostridium
by product is water vapor and oxygen which are non toxic
low penetration -> use PEG or dimethyl formamide which act on outer layer of bacteria/ virus
what are the disadvantages of ETO
flammable and explosive, cause eye pain, sore throat, difficulty breathing and blurred vision, dizziness, nausea, headache, convulsions, blisters, vomitting, coughing, potentially carcinogenic
what are the disadvantages of peracetic acid
have to add another anticorrosive agent -> must make sure to remove
affected by organic residue -> require high conc for effect
wide rand of efficacy depending on microorganisms
what is a diffusion enhancer
small vial of more conc h2o2 that can be used for product with lots of small pipes
what is gamma radiation
sterilisation by ionising radiation, primarily by cobalt 60/ cesium 137/ electron accelerators
what is gamma radiation often used for
medical products and packaging materials
what are the characteristics of gamma radiation
low temperature sterilisation, cheaper and easier to set up, disrupts nucleic acid, suitable penetration and high dose rate
what can gamma radiation pass through and what can it not pass through
can pass through aluminium, paper, plastic, medical device packaging
cannot pass through lead
what are the disadvantages of gamma radiation
not suitable for aq products with proteinaceous components as can form products with proteins present, can cause oxidation, delamination and cracking in polyethylene
what is the structure of ozone
consist of O2 with a loosely bonded third O atom
what is the property of the loosely bonded third O atom in ozone
powerful oxidant that destroys microorganisms but is highly unstable, more effective than h2o2
any residue of ozone can be removed by simply leaving product in sterile chamber for a few mins
what is the half life of ozone
22 mins at room temp
what is ozone compatible with
wide range of commonly used materials like stainless steel, titanium, aluminium, ceramic, glass, silica, PVC, polyethylene, polypropylene, acrylic
what are examples of airborne bacteria
TB, varicella, aspergillus
what are examples of contact bacteria
s. aureus, enterococci, gram neg bacilli
what are examples of common vehicle bacteria
food poisoning, salmonella, hepA
what are the bacteria associated with vascular devices leading to nosocomial infections
s. aureus/ epididermis
group B strep
VRE
MRSA
e. faecalis
acinetobacter
klebsiella
candida
enterobacter
what are bacteria associated with ventilators leading to nosocomial infection
s. aures
MRSA
proteus
serratia
pseudomonas
stenotrophomonas maltophilia
what are bacteria associated with surgical site infections leading to nosocomial infections
s. aureus
gram neg bacilli
what are the considerations in preventing nosocomial infections
- limiting transmission of microorganism between patients in direct patient care through adequate cleaning, PPE, prophylactic antimicrobial, training, isolation
- controlling environmental risks
- limiting the risk of endogenous infections by minimising invasive procedures and promoting optimal antimicrobial use
- surveillance of infections, identifying and controlling outbreaks
- preventing infections in staff members
what are the categories for risk of infections -> what type of patients and procedures fall under each category -> what type of disinfectants can be used
category 1 (minimal):
- not immunocompromised, no significant underlying disease
- non invasive, no exposure to biological fluids
- alcohol, sodium hypochlorite, phenol, iodophor
category 2 (medium):
- infected patients or patients with some risk factors
- invasive non surgical procedures (urinary catheter, peripheral venous catheter), exposure to biological fluids
- alcohol, sodium hypochlorite, phenol, iodophor
category 3 (high):
- severely immunocompromised (<500WBC/ml), multiple trauma, severe burns, organ transplant
- surgery or high risk invasive procedures (central venous catheter, endotracheal intubation)
- glutaraldehyde, ortho-phthalaldehyde, h2o2 gas at 7.5%, h202/peracetic acid
what are the roles of the pharmacist
- storing and distributing pharmaceutical preparations using practices that limit potential transmission of infectious agents to patient
- dispensing of anti-infectious drugs and maintaining relevant records (potency incompatibility, conditions of storage and deterioration)
- storing vaccines and making them available as appropriate
- maintaining records of abx distribution to medical departments
- provide summary reports and trends on antimicrobial use
- ensuring following information available for disinfectants, antiseptics and other anti-infectives
- active properties (conc, temp, length of action, abx spectrum)
- toxic properties
- incompatible substances that affect potency
- unfavourable physical conditions for storage (temp, light, humidity)
- harmful effects on materials - participate in development of guidelines for antiseptics, disinfectants
- participate in development of guidelines for reuse of patient materials and equipments
- participate in quality control of techniques used to sterilise equipments
