Disinfection and sterilisation Flashcards
Define: Antisepsis
Destruction or inhibition of microorganisms on a living tissue
Define: Sanitisation
Reducing microbial population on inanimate objects to safe levels
Define: Disinfection
Process that eliminates many or all pathogenic microorganisms on inanimate objects: Exception of bacterial spores
Define: Sterilisation
Physical or chemical process that completely destroys or removes all forms of viable microorganisms: Removes spores
Define: Biocidal
Action which kills micro-organisms
Define: Biostatic
Action which inhibits growth
List the levels of risk with the description, and removal method.
Critical:
• Entry or penetration into sterile tissue, cavity or bloodstream
• Sterilise
Semi- critical:
• Contact with intact nonsterile mucosa or non-intact skin
• Sterilise OR high level chemical disinfection
Non- critical:
• Contact with intact skin
• Disinfect
What are the types of sterilisation methods?
- Physical
* Chemical
Describe physical sterilisation methods?
- Dry heat: 160°C, 2 hrs + heating time
- Wet heat (Autoclave): 121°C, 10-12 mins + heating time; 132°C, 3 mins + heating time
- Radiation eg. UV (260 nm), gamma irradiation
- Filtration (0.22 μm pore size)
Describe chemical sterilisation methods?
Gas phase:
• Ethylene oxide (38°C)
• Hydrogen peroxide vapour (4-80°C)
Liquid phase:
• 2% Glutaraldehyde
• 37% Formaldehyde
• Hydrogen peroxide
What are the mechanisms behind microbiocidal activity?
- Cell membrane disruption
- DNA damage: degradation; oxidation; alkylation; thymidine dimer
- Protein damage: denaturation; oxidation; crosslinking; alkylation
- Lipid oxidation
What factors affect the efficacy of sanitisation?
- Number of micro-organisms and their access
- Resistance of the micro-organisms
- Concentration & potency
- Physical & chemical factors eg. temperature, pH, humidity, water hardness
- Organic matter
- Duration of exposure (time)
- Biofilms
