Sterilization and validation. Richard Marchand MD Medical Microbiologist and Infectious Diseases Assistant Professor University of Montreal One hospital (The CSSSSVLDLJ) Somewhere in Quebec. Plan. History Basic definitions A lot of little quizzzz Properties of heat, steam and bugs
Richard Marchand MD
Medical Microbiologist and Infectious Diseases
University of Montreal
One hospital (The CSSSSVLDLJ)
Somewhere in Quebec
Answer : It depend on the bacteria because some are highly resistant to heat.
(Ex.: Geothermal bacteria like hot spring bugs withstand 250 oC )
Most human pathogens were thought to be killed by temperature lower than 150 oC.
FDA : FOOD and Drug Agency
What is oxidation ?
Will discuss that later
100 °C : fresh water in a pan with a lid
97 °C : fresh water in a pan without a lid
104 °C : sea water (depending on salt concentration)
Why 2 or more exposures to heat ?
Answer : For germination to happen
Why « no air » ?
Answer : Because the air blocks the energy transfer toward organic matter.
So lets screen them and use the most resistant and predictable safe bug that can be “canned” to design safe processes.
N.B. Faster does not mean more efficient, because a bug killed more slowly is not less dead.
For a BI of : 2.0 X 106 et Dvalue* of 1 minute
*At that time the most resistant Bacillus know was the stearothermophilus with a Dvalue of 1 to 1.5
Cycle of 6.5 minutes
More we have cans, more we have contaminated cans !
So lets double the time, to bring back the survival probability once again around 0 – 0.2
(The overkill approach was born)
Question : Is all processes D values a time dependant measure ?
Answer : No, for radiation and ozone sterilization the Dvalue is dose dependant
1965 The Swedish National Health Board proposed : Sterility Assurance Level (SAL) 10-6
SAL = Sterility Assurance Level
For a BI of : 2.0 X 106 et Dvalue of 1 minute
Cycle of 6.5 minutes
More we have packs, more wont pass !
Question : Can you name a heat barrier material ?
Answer : polymers (plastics) like non porous plastic containers, wood, rubber etc..
Preferred by many for orthopaedic steel and metallic devices
Sterilization 3.5 to 15 min
Dry time 15 to 20 minutes max.
In all cases, for them to work, water is required to a certain level. No water molecules, to little or to much will hamper these process.
Name the critical parameters of steam sterilization
BIOLOGICAL KILL (HALF-CYCLE)
This is presuming all mechanical aspects of your process are working the way they should and you are getting adequate saturated steam.
What is the difference between steam at 100oC and humidity at 100oC ?
What is the difference between 0oC ice solid water and et 0oC liquid water ?
Can water exist as a gas at temperature lower than 0oC ?
Can water not be steam at temperature higher than 100oC ?
For a given temperature
All gases in presence of water have some of it in a gaseous state called humidity.
Humidity is an intermediate between the steam (the energy source) and the organic material (the target)
Humidity acts as the transient energy buffer transferring state that permits proteins denaturation called “hydrolysis”
Low energy vapour
High energy vapour
One or two degrees of temperature drop here…
Releases hundreds of calories of heat here.
If to much energy is released the steam goes back to liquid water ( full condensation) = the devices will be wet.
A very fine tuning line to control
Sterilisation validation is arbitrarily laid on the construction of an cycle based on the behaviour of biologic indicators hopped to be « predictable »
It is a device conceived to verify if the process operated as expected
For the same reasons we wash the plates in standing position (specialy with gravity cycles)(unwrapped material)
Avoid stacking up
Avoid “asparagus assembly”
Question : Are you sure that things are sterile under the rubber bands
Hardness according to regions