IC9 Sterilization Methods Flashcards
What is the mechanism of action of moist heat sterilisation?
Destroys microorganisms by the irreversible coagulation and denaturation of enzymes and structural proteins
What are the 4 parameters that affect steam sterilisation?
1) Steam; ideally dry but saturated (97%) & entrained water
2) Pressure (necessary to achieve high temperature)
3) Temperature (usually 121°C or 132°C)
4) Time (temperatures must be maintained for a minimal time to kill microorganisms)
3 types of autoclaves for moist heat are?
Gravity displacement autoclave, High-speed prevacuum steriliser, Steam flush-pressure pulsing
What is the measure of efficacy for moist heat sterilisation?
D value
How do you determine exposure time required for moist heat sterilisation?
F concept which determines an equivalent time whereby exposing the object at a certain temperature for a certain duration of time is equivalent to exposing it at the pharmacopeial specifications (most of the time 121 degC for 15 minutes)
How to calculate F?
F= ∆t × 10^((T-Tref)/Z)
F= 15 × 10^((T-121)/10) for pharmacopeial specifications
When is dry heat sterilisation used?
Used for materials that might be damaged by moist heat or that are impenetrable to moist heat (like powders, petroleum products, sharp instruments)
Name the disadvantage(s) of using dry heat sterilisation
1) Slow rate of heat penetration (air not as good a thermal conductor compared to water)
2) High operating temperature may not be used on all objects
State the types of dry heat steriliser as well as which type is more efficient
Static air (Slower in heating, requires longer time to reach sterilizing temperature, and is less uniform in temperature control throughout the chamber compared to forced-air) –> less efficient
Forced air (more rapid transfer of heat)
State when would chemical sterilisation be preferred
When sterilising heat-sensitive medical devices and surgical supplies
State the chemical sterilants used in chemical sterilisation
ethylene oxide, formaldehyde, hydrogen peroxide fog and peracetic acid
State the activity of paracetic acid
Active against bacteria, fungi and yeast (but NOT viruses)
What are the disadvantages of using paracetic acid?
1) Need anticorrosive agent
(highly acidic; metal medical devices may not be as affected as much but plastic more sensitive to corrosion). Need to include another excipient to remove the anti-corrosive agent after the formulation process
2) Affected by organic residue (may react with organic compound rather than with bacteria)
How are gas plasmas generated?
Generated in an enclosed chamber under deep vacuum using radio frequency or microwave energy to excite the gas molecules and produce charged particles, many of which are in the form of free radicals
What are the advantages of using gas plasma as sterilisation?
1) Wide range of efficacy including mycobacteria, MRSA and clostridium
2) Non-toxic (by products are water vapor, oxygen)
3) Good for temperature sensitive products
