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Moist heat sterilization
Moist heat sterilization relies on steam or boiling water to achieve high enough temperatures to kill microbes. The most common method is autoclaving, which uses saturated steam under pressure to safely exceed the boiling point of water. Autoclaving is preferred over other moist heat methods unless heat or moisture will damage the material. Biological indicators containing bacterial spores are used to monitor whether an autoclave process achieved sufficient sterilization conditions.
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Moist heat sterilization
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- 2. Principle-Denaturation & coagulationof proteins due to the latent heat present in steam Advantages of steam –Latent heat liberated on condensing on a cooler surface increases the temprature of that surface What is Moist heat Sterilization? 6/11/2013
- 3. Types of Moistheat Sterilization • Pasteurization • Inspissation or Fractional Sterilization Hot water below boiling point • Tyndallization or Intermittent Sterilization Boiling water /steam at atm pr • AUTOCLAVESaturated steam 6/11/2013
- 4. Pasteurization 6/11/2013 • 63 Cfor 30 minutes Holder Method •72 C for 15- 20 seconds Flash Process Heat labile fluids may be disinfected
- 5. It is theprocess of thickening by dehydration 6/11/2013 Inspissation Media such as Lowenstein –Jensen media and Loeffler’s serum are rendered sterile by heating at 80-85 C for half an hour on three consecutive days
- 6. 6/11/2013 Tyndallisation Principle: The firstexposure kills all vegetative bacteria and the spores since they are in a favourable medium will germinate and be killed on subsequent occasions Though generally adequate this method may fail with spores of certain anaerobes and thermophiles
- 7. The Autoclavewas invented by Charles Chamberland in 1879 AUTOCLAVE 6/11/2013
- 8. Definition Autoclave is apressurized device designed to heat aqueous solutions above their boiling point at normal atmospheric pressure to achieve sterilization 6/11/2013
- 9. Reliable sterilization withmoist heat requires temperatures above that of boiling water. These high temperatures are most commonly achieved by steam under pressure in an autoclave. . Need for autoclaving: 6/11/2013 Autoclaving is the preferred method of sterilization unless the material to be sterilized can be damaged by heat or moisture
- 10. 6/11/2013 Liquid H2O cannotbe heated above 100°C in an open vessel At 100°C boils H2O heated in a sealed vessel Pressure rises Boiling point of H2O is raised
- 11. 6/11/2013 Air removal Downward displacement Steampulsing Vacuum pumps Superatmospheric Subatmospheric Process
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- 13. Biological indicators arethe only process indicators that directly monitor the lethality of a given sterilization process. Spores used to monitor a sterilization process have demonstrated resistance to the sterilizing agent and are more resistant than the bioburden found on medical devices. Bacillus stearothermophilus Thermophilus aquaticus Spore Test 6/11/2013 If the autoclave does not reach the right temperature the spores will germinate when incubated and their metabolism will change the color of a pH –sensitive chemical.
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