MICROBIOLOGY- Destruction of micro-organisms - sterilisation and disinfection Flashcards
Define decontamination
Decontamination is a combination of processes that removes or destroys contamination so that infectious agents or other contaminants cannot reach a susceptible site in sufficient quantities to initiate infection or other harmful response
Define sterilisation
Complete killing or removal of all types of micro organism (including spores)
Give examples of micro organism
- Eukaryotes
- Prokaryotes
- Viruses
Define anti sepsis
Disinfection applied to damage skin or living tissues
Define sanitisation
Removal of microbes that pose a threat to public health
Give examples of sterilisation methods
- Heat
- Chemicals
- Irradiation
- Filtration
How can we use heat to sterilise something
- Moist heat
2. Dry heat
What is the moist heat method of sterilisation
- Boiling,
- Autoclaving
- Exposure to super heated steam at controlled press and temperature cycle
Which is more effective autoclaving or boiling? Why?
Autoclaving as you can set the temperature and how long you want to sterilise something for eg 115 degrees at 30 mins or 134 degrees for 3 mins
How do autoclaves work
The air displacement method
Name the two sub types of the air displacement method
- Passive (type N) for unwrapped instruments
2. Vacuum (type B) for wrapped instruments
After sterilisation what is it important that we do?
Quality control to make sure the equipment has been sterilised properly
Name some different methods we can evaluate the efficacy of an autoclave machine
- The Bowie- Dick Test
Name some problems that can occur in an autoclave and what they can cause
Air leakage
Unwanted condensation
These can result in cold spots which will mean the equipment isn’t properly sterilised
Which of the 2:
dry heat exposure or autoclave saturated steam
Need a longer time to effectively sterilisation material
Dry heat needs longer
It runs t higher temperatures for a longer time Rame in comparison to autoclaves
Eg 160-170 degrees for 2 hours
When is it better to use dry heat over moist heat to sterilise something?
- When using metal as dry heat is not corrosive to metal
2. Some glass ware may get damaged in steam so better to use a dry heat method
Give examples of gas chemicals we can use for sterilisation
Ethylene oxide
Give examples of liquid chemicals we can use for sterilisation
Glutaraldehyde
formaldehyde
Name the irradiation we use to sterilise equipment
- Ultraviolet
2. Gamma radiation
Describe Ethylene oxide and how we use it for sterilisation
It is a highly flammable gas
We usually mix it with 90% CO2 to prevent it from igniting
useful in killing spores and bulky items that can’t fit into an autoclave
What is the main problem with Ethylene oxide?
It is highly flammable
Takes a long time to dissolve from surfaces so stays on the sterilised surface for some time after sterilisation
Give some disadvantage of using Glutaraldehyde
It can become inactivated in the presence of organic matter
It is very toxic so not commonly used
How is formaldehyde used?
Can be used in solution or as a vapour
When is formaldehyde used?
When a large area has been contaminated or when contaminated equipment like extractor fans are hard to reach
How does radiation get rid of microorganisms
It affects and breaks down their DNA leading to micro organism cell death
When is ultra violet used as a sterilisation method
To sterilise surfaces or air
What does ultraviolet not go through?
Glass due to its wavelength
What is gamma irradiation sometimes referred to as?
Cold sterilisation