Sterilization (microbiology)

Sterilization (microbiology) is a process that eliminates, removes, kills, or deactivates all forms of life and other biological agents (such as fungi, bacteria, viruses, spore forms, prions, unicellular eukaryotic organisms such as Plasmodium, etc.) present in a specified region, such as a surface, a volume of fluid, medication, or in a compound such as biological culture media.

Methods of Sterilization

Sterilization can be achieved through various means, including heat, chemicals, irradiation, high pressure, and filtration. The method chosen must be appropriate to the item being sterilized.

Heat

Heat is one of the most common methods of sterilization. It is used in two forms: moist heat and dry heat.

• Moist Heat: Moist heat sterilization involves the use of steam that is free from air, as air is considered an insulating medium. Autoclaving, the most commonly used form of moist heat sterilization, involves subjecting the item to be sterilized to steam at a temperature of 121-134 degrees Celsius for about 15-20 minutes depending on the size of the load and the contents.

• Dry Heat: Dry heat sterilization, also known as hot air oven, is used for materials such as glassware, which can withstand high temperatures, and materials that are not suitable for moist heat sterilization. The temperature used for dry heat sterilization is usually higher than that for moist heat sterilization.

Chemicals

Chemical sterilization uses lethal gases and liquids to kill microorganisms. These chemicals include ethylene oxide, formaldehyde, glutaraldehyde, hydrogen peroxide, peracetic acid, and others.

Irradiation

Irradiation sterilization can be achieved by ionizing radiation (gamma rays or electron beams) or non-ionizing radiation (ultraviolet light). This method is used for a variety of applications, including food sterilization and sterilization of medical devices.

High Pressure

High pressure sterilization, or high-pressure processing, is a method of sterilizing packaged food products by subjecting them to a high level of isostatic pressure.

Filtration

Filtration sterilization is used for heat-sensitive materials. This method removes microorganisms rather than killing them.

Applications

Sterilization is essential in healthcare settings and is also used in microbiology, veterinary science, mycology, and dentistry. In the food industry, sterilization helps to reduce spoilage and improve product shelf life.

See Also

• Disinfection
• Pasteurization
• Antisepsis
• Aseptic technique

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  Contamination on agar plate
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  Joseph Lister c. 1855
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  Apparatus for sterilizing surgical instruments
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  Hot air sterilizer
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  Chemiclav
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  E-beam, X-ray, and gamma efficiency
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  Curette in sterile packaging