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FACTORS AFFECTING EFFICACY IN STEAM STERILIZATION (TIME (Exposure…
FACTORS AFFECTING
EFFICACY IN STEAM
STERILIZATION
TEMPERATURE
How?
T ∝ P
Effect
Higher the temperature, shorter sterilization time
80°C :arrow_right: 643 hours
Material
Glass & Metal
NOT plastics, papers & clothes
TIME
D-value:15 to 30 minutes at 121 degree celcius
Exposure phase for SAL of 10-4:
20 min 121 °C
Indicate that only 1 chance spore can survive in 10,000 products
Geobacillus stearothermophillus
(Bst) spores is used as biological indicator
Why?
Can withstand high degree of temperature
Increase of time by 2 minutes will decrease SAL by a factor of 10
The longer the time, the better
DSC DIRECT STEAM CONTACT)
Steam contain very high amount of energy
To produce steam
Additional 2,257 kJ/kg is needed compare to only 419 kJ/kg is needed to boil water from 0 °C to 100 °C
Steam must be condensed onto the item surface
So, the energy will be transferred form steam to the items. Then, the items will be sterilized (by killing the microbes)
Steam need to be in direct contact with the item that need to be sterilize
MOISTURE
Induce denaturation or coagulation of protein
Avoid
Superheated steam
Ensure steam source pressure between 30-35 psi
Set autoclave jacket temperature lower than chamber temperature
Steam supply not more than twice of chamber pressure
Wet steam
Contaminated steam
Use clean and saturated steam
DRYING
Importance
Moisture must be removed from the sterilized item before being unloaded to prevent recontamination
How?
Pressure is lowered until the entrapped water inside the items boils and evaporates, leaving the items completely dried
Crucial step in post conditioning phase
AIR REMOVAL
Use super atmospheric positive pulse
Replacing air inside the chamber completely with dry saturated steam
Chamber able to reach 100°C
Pressurized chamber
30 seconds duration
Initial air removed, dry saturated steam pumped in, air pumped out
Precaution
Bowie- Dick test pack
Chamber leak rate test
Drain- mounted air detector
Use non-condensable steam
To increase the temperature, the pressure in the autoclave need to be increased
Example
121°C :arrow_right: 12 minutes
