Contamination Control Flashcards
Why do microorganisms pose a problem to pharmacists?
- small
- abundant and can grow in the most unlikely situations
- may cause disease - pathogenic
- some form spores, which are resistant to killing by heat, chemical, radiation or drying
Describe bacteria.
- 0.7-4mcm
- unicellular
- rod shaped or spherical
- gram +/-
- nutrients: C, H, N, O, S, P, water
- aerobic/anaerobic
Describe bacterial spores.
- undergo a rpofound biochemical change
- lead to formation of spore
- highly resistant to adverse environemtn
Describe viruses.
- 20-250nm
- most pass through bacteria proof filters
- destruction by heat
- most inactivated at 60°C for 30 mins
- all killed by boiling water
- most chemical disinfectants have minimal virucidal activity
Describe fungi.
- single or multicellular
- single - 5-10mcm in diameter
- commonly form spores
- yeasts, moulds and mushrooms
Describe the air supply in aseptic areas.
areas have to be supplied and continuously flushed with air of suitable quality and at a positive pressure
achieved through High Efficiency Particulate Air (HEPA) filters of appropriate efficiency
Describe the cleanroom specifications.
- air wuality standards in aseptic processing areas must meet both US and European requirements
European standards:
- Grades A, B, C and D classifications, instead of 100,1000
- use particle and microbial limits per cubic metre, instead of cubic foot
- require particle measurements at 5 microns in addition to 0.5 microns in grade A and B areas
- differentiate area cleanliness dynamically “in operation” and ‘at rest’
*
How can you measure aerial contamination?
- settle plates
- Slit Samplers
Describe the use of settle plates.
- nutrient plates which collects aerial contamination >100mcm which settle by gravity
- important hazard in aseptic work
- small particles not represented
- unaware of volume of air introduced
Describe the use of Slit Samplers.
- air drawn through a slit or number of small holes
- beneath which rotates a “nutrient” agar plate
- deposition of particles depends on the rate of air flow, slit width, or dimensions of holes and distance between slit/holes and plate
- 99% efficiency of particle - 1mcm
- can count number of organisms associated with particles in a known volume of air drawn through the device
What needs to be monitored in aseptic areas?
- particulate contamination
- temp & humidity
- air velocity and pressure
What is required from those who work in aspetic areas?
- high standards of personal hygiene and cleanliness
- any medical condition (colds, skin infections) should be reported
- min. number of people should be present when work in progress
- adequate training
- gowning up
What happens when viable cells are exposed to a lethal agent?
constant proportion, not a constant number of organisms are killed per unit time
plotted as:
- log number of viable cells
- log % viable cells against time
Steriling conditions should produce what probability level?
a probability level of one in one million units being non-sterile (based on linear death kinetics)
What is the sterility assurance and what does it mean?
10-6
degree of assurance with which the process in question renders a population of items sterile
SAL 10-6 = probability of not more than one viable organism in 1 x 106 sterilised items of final product
What is a D value?
decimal reduction value
value of a parameter of sterilisation (duration or absorbed dose) required to reduce the number of viable organisms by 90% or 1 log cycle
What is inactivation factor and how do you calculate it?
reduction in the number of viable organisms produced by sterilising process
10t/D
t = exposure time
D = D value
Describe the two approaches to sterilisation.
- overkill method
- sterilisation cycles based on inactivation of a greater N of organisms of greater resistance than the natural bioburden of the product
- minimum SAL set for cycle
- basis of traditional BP methods of heat sterilisation
- with recomended combinations of time and temp
- bioburden method
- requires knowledge of bioburden, D value and most resistant organism
- prior to defining the sterilising cycle
- allows sterilisation cycles to be run with acceptable SALs and minimal product detoriation
What is the bioburden?
number of viable organisms a batch contains
What is terminally sterilised vs non terminally sterilised products?
- terminally sterilised
- products sterilised in their final container
- method of choice whenever possible
- manufactured in cleanroom
- pyrogen free product
- low microbial and particulate counts prior sterilisation
- non-terminally sterilised
- prepared under aseptic conditions from previously sterilised materials
- processed in cleanrooms
- until sterilised
- filled into final container in aspetic areas
What are examples of terminally sterilised vs non terminally sterilised products?
terminally sterilised:
- steam sterilisation (heating in autoclave)
- dry heat sterilisation
- ionising radistion sterilisation
non-terminally sterilised:
- filtration
Describe heat sterilisation.
- most reliable, versatile and readily available and economic method of sterilisation
- materials must be stable
- heat decomposition of drug, interaction between drug and additives, modification of pharmacological activity of drug
- stability of containers and closures
- safer compared to chemical sterilisation
net result depends on balance between
- heat increasing rate of chemical reactions within bacteria cells = increased growth rate
- destructive effect on more heat sensitive components of cell
What is bacteriostasis?
point at which organisms die at the same rate they reproduce
What is a further increase in temp past bacteriostasis point called?
destructive bactericidal effect
death rate increased and time to sterilise decreased
What is one bad thing about vegetative bacteria?
relatively heat sensitive
killed rapidly in hot water at 60-100deg
spores usually require temp greater than 100deg
What can be used as a biological indicator to test the efficiency of sterilisation processes and why?
bacillus stearothermophilus
very heat resistant
Describe the mechanism of destruction of moist heat.
- hot air with water vapour
- unfolding protein = protein denaturation = uncoiling DNA = enzyme inactivation
- changes to cell membrane = leakage of cell contents = death
- relatively lower temp than dry heat
Describe the mechanism of destruction of dry heat.
- absence of water
- proteins much more stable - more enrgy required for unfolding
- death occurs by
- oxidation of cell components
- requiring high temp
What sterilisation process is preferred in BP?
saturated steam under pressure
saturated steam: water vapour at a temp corresponding to the boiling point of water appropriate to its pressure
What temp and time is required for steam sterilisation?
for aqueous preparations: a minimum of 121 deg for 15 mins
Define sensible heat.
heat required to raise the temp of water to its boiling point
Define latent heat.
additional heat, absorbed when boiling water is converted to steam at the same temp
What are advantages vs disadvantages of moist heat?
+
- terminal sterilisation
- any dose volume
- good safety margin
- virsuses killed
- relatively short progress
- suitable for dressings, rubber and some plastics
- suitable for solutions, suspensions, surgical materials
-
- unsuitable for themrolabile materials, anhydrous materials (oils and powders)
- organisms killed but not removed
- skilled operators required
- may damage glass and metal
- batch process
Describe dry heat sterilisation.
- terminally sterilised
- temp 160-180 for 30 mins-2 hours
- used for thermostable items - sensitive to moisture or impermeable to steam
- very high temp (250deg) used to sterilise and depyrogenate glassware
- anhydrous materials
- glass and metal materials
- powders
- some rubbers
Why is terminal sterilisation preferred?
provides a SAL that is possible to calculate, validate and control
incorporates a saftey margin
What are advantages vs disadvantages of dry heat?
+
- terminal sterilisation
- any dose volume
- viruses killed
- used for anyhdrous material
- sutiable for suspensions and solutions
- less damage to glass and metal than moist heat
-
- drastic heat treatment
- organisms killed but not removed
- unsuitable for dressings, rubber and plastics
- suspensions may give different crystal form on cooling
What is sterilisation by filtration?
- API and preparations not sufficiently heat stable to allow autoclaving (thermolabile)
- passage through a sterile membrane filter of normal pore size0.22mcm or less
- organisms removed, instead of killed
- doesnt sterilise: suspensions, medicaments highly adsorbed by filters, readily oxidised solutions, products unstable in solution
What are advantages vs disadvantages of filtration?
+
- no thermal effects
- remove dead and viable organisms
-
- difficult technique
- require sterility testing prior to release = delay
- will not remove or inactivate viruses
- defects in filters not visible
- possibility of adsorption of medicament, liberation of particles or alteration of pH by the filter
- unsuitable for suspensions
What is ionising radiation sterilisation?
- terminal sterilisation
- minimum adsorbed dose of 25 kGy
- gamma radiation - very penetrating
- beta radiation (high speed electron) - poor penetration
- physical and biochemical effects in microorganisms (DNA)
- used for: heat sensiitve materials (disposables, dressings, organic compounds (antibitoics, hormones))
What are advantages vs disadvantages of ionising radiation sterilisation?
+
- operates at ambient temp
- terminal sterilisation
- concinuous process
- reliable and accurately controlled
- treatment time short - few seconds
-
- expensive
- damaging effect on some materials (glass, plastic, PVC)
- protective precautions
What gas can be used for sterilisation?
ethylene oxide
What are the principles of good manufacturing practise?
- qualified personell
- adequate premises
- suitable production equipment, designed for easy cleaning and sterilisation
- validated procedures for all critical production steps
- environmental monitoring and in process testing procedures
- precautions to minimise pre sterilisation bioburden
