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Explain the Methods of sterilization.

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1. Autoclaving – media and other items that are sterilized by exposure to steam at 1210C and 15 psi of pressure for 15 minutes or longer depending on the nature of the item.
- Under these conditions, microorganisms even endospores will not survive longer than 12-13 minutes (method is rapid and dependable)
- The autoclave is designed to ensure all the air is expelled and only steam is present in the autoclave chamber.
- The equipment is temperature controlled.

2. Dry heat sterilization – steam tends to dampen glassware such as pipettes and petri plates.
- Such glassware / items are placed in an electric oven set to operate between 1600 and 1700c for about 2 hours or longer (since dry heat is not as effective as wet heat)

3. Ultra violet (UV) radiation
- UV around 260 nm is lethal to many microorganisms but does not penetrate glass, dirt, films, water and other substances effectively.
- UV is therefore used in few situations e.g UV lamps placed on the ceilings of rooms or in biological safety cabinets to sterilize the air and any other exposed surfaces.

4. Ethylene Oxide gas – used to sterilize heat sensitive items e.g disposable plastic petri dishes and syringes, catheters, sutures.
- The gas is both microbicidal and sporicidal – kills by attaching to cell proteins
- Its effective sterilizing agent because it rapidly penetrates packing materials even plastic wraps.

5. Bacteriological filter – used to sterilize media whose components cannot withstand heating at 1210c.
- Physically removes bacteria and larger microorganisms from the solution and sterilizes
them without heat. e.g. Sintered glass filters with ultra-fine filter disks 0.9 to 1.4 um pore size. Seitz asbestos – pad for funnels (3mm thick with 0.1 mm pore are effective – sterilizing Solutions)
Generally membranes with 0.22 mm pores are used in sterilization.

Kavungya answered the question on March 13, 2019 at 05:53

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Explain the Methods of sterilization.

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