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Sterilisation and Disinfection

Sterilisation and Disinfection. Lab 5. Sterilisation and Disinfection. Sterilisation Killing or removal of all living organisms in or on a substance or object, usually be denaturing proteins, nucleic acids and membrane permeability Disinfection

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Sterilisation and Disinfection

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  1. Sterilisation and Disinfection Lab 5

  2. Sterilisation and Disinfection • Sterilisation • Killing or removal of all living organisms in or on a substance or object, usually be denaturing proteins, nucleic acids and membrane permeability • Disinfection • Killing of most microorganisms on a substance or object (kill may not be complete – removes a high % of organisms to numbers too low to cause disease) • Sterile techniques • Procedure carried out in the absence of living things • Aseptic techniques • Procedures performed in a way to prevent contamination with infectious microorganisms

  3. Methods of sterilisation • Heat • Dry – hot air oven 160 deg. • Moist – Autoclave 121 deg. /20 min • Ionising radiation – disposable plastics, surgical materials, unsuitable for glass and metal • Filtration • Chemicals • Ethylene oxide • Formaldehyde • Hydrogen peroxide • Chlorine dioxide • Peracetic acid

  4. Heat - Denatures enzymes • Thermal death point (TDP): lowest temp at which all microorganisms are killed in 10 minutes • Thermal death time (TDT): minimal length of time in which all bacteria will be killed • Decimal reduction time (DRT): time, in minutes, in which 90% of a population of bacteria at a given time will be killed • Moist heat • Coagulation of proteins and breakage of H bonds • Boiling • kills all vegetative cells, most viruses and fungi within 10 minutes

  5. Steam under pressure • 121°C • Kills all microorganisms and their endospores in about 20 minutes • Monitor efficacy of Autoclave • Bacillus stearothermophilus spores

  6. Pasteurization • 63°C for 30 minutes • 72°C for 15 seconds (high temperature short-time (HTST) pasteurization • ultra-high-temperature (UHT) treatment

  7. Factors affecting the action of disinfection • Period of exposure • Concentration • Temperature • pH • Organic matter • Number of bacteria present

  8. Disinfection • Chemicals, as well as those used for sterilisation: • Alcohols • Dyes • β-propiolactone • Cholorhexidine • Hydrogen peroxide • Hypochlorites • Mercury compounds • Phenolics • Tetrachlorosalicilanide (TCS) • Variety of mode of action on bacterial cells

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