Sterilization And Disinfection

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Sterilization:

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is complete killing or removal, of all living organisms (including highly resistant bacterial spores) from a particular location or material.

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Disinfection:

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is the destruction of pathogenic microorganisms by processes that fail to meet the criteria for sterilization.

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Disinfectants

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are chemical compounds that are used to kill microorganisms on inanimate objects

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Antiseptics:

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are disinfectant agent that can be used on the body surface such as the skin. They have lower toxicity than disinfectants used environmentally

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Methods of sterilization and disinfection:1-

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Physical methods. 2- Chemical methods.

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PHYSICAL METHODS

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A. HEATB. RADIATIONC. FILTRATION

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HEAT

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1. DRY HEAT:

2. MOIST HEAT:

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1. DRY HEAT:

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Hot air oven: it uses a temperature of 180 C for 2 hours.This method is used for sterilization of glass-ware and powders.b. Red heat: It is carried out by holding the object in a flame until red hot, e.g. sterilizing bacteriologic loops .c. Incineration:for discardable items.

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MOIST HEAT

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Moist heat at temperature below 100C: e.g. Pasteurization of milk, by heating to 63οC for 30 minutes or to 72οC for 20 seconds.By this method Mycobacterium and Salmonella and Brucella abortus can be killed

Moist heat at temperature of 100C : Boiling at 100C for 20 min., used for disinfection of surgical and medical equipments e.g. forceps and scissors Steaming at 100οC : Koch’s steamer .Steaming is done by a single exposure for 60-90 minutes.Or by three successive exposures for 3 successive days, each exposure takes 20-30 min.This is known as tyndallization.

Moist heat at temperature above 100C: - Autoclaves: In autoclave, water is heated at double atmospheric pressure , temp. will be raised to 121C and applied for 20-30 min.Or at 3 atmospheric pressure the temp. will be raised to 134C and applied for 3-6 min. Autoclave is used for the sterilization of surgical instruments, bed linen, surgical dressings and cotton.

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Types of autoclaves

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The simple autoclave.b. Steam jacketed gravity displacement autoclave.c. Prevacuum autoclave.d. Flash autoclave

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B-RADIATION

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Ionizing radiation:

Non-ionizing radiation

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FILTRATION

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This is a mechanical removal of microorganisms from fluids which are damaged by heat: e.g. serum, plasma

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Types of filters

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Membrane (Millipore) filters.b. Air filters.c. Vacuum filtersd. Syringe filterse. Sintered glass filters

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CHEMICAL DISINFECTION AND STERILIZATION

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Ethyl alcohol, used as antiseptic3-Chorine, used as disinfectants of water.4-Iodine, used as antiseptic.5-Hydrogen peroxide, used as antiseptic.6-Glutaraldehyde, used as disinfectants,in concentration of 2% for 5 minutes.Also ,Glutaraldehde is used as sterilizer, in concentration of 10% ,for 7 hours.7-Heavy metals e.g. mercury and silver, both are used as antiseptics.8-Ethylene oxide gas, used as sterilizer.