Sterilization And Disinfection Of Microorganisms

Sterilization is defined as the process by which an article, surface or medium is freed from all living microorganisms either in vegetative or in spore state.

Microorganisms are ubiquitous (present, appearing or found everywhere). Because some off them causes contamination, infection and decay of organic matter, it is necessary to remove them from certain areas. From here need of sterilization begin.

The process of sterilization may differ as per the requirement like in microbiology it is done to prevent contamination from extraneous organisms, in surgery it is done to maintain asepsis, in food and drug industry sterilization is done for ensuring safety from contaminating organisms. So the method of sterilization depend on the purpose of sterilization, the material which has to be sterilized and the nature of microorganism that are to be removed or destroyed.

Disinfection is one of the common method to do rapid sterilization. Disinfection means the destruction or removal of all pathogenic organisms, or organisms capable of giving rise to infection. The term antisepsis is used for the chemicals those prevent the growth of bacteria in wounds or tissues. Chemical disinfectants which can be safely applied to skin or mucous membrane and act to prevent growth of bacteria are called antiseptics.

Antiseptics can only be applied on the outer surface of the skin no open wound or cut on skin. However antisepsis can be applied on wounds to prevent the growth of bacterial colony.

Bactericidal agents or germicides are those agents those which are able to kill bacterial colonies. Bacteriostatic agents only present the multiplication of bacteria which may left bacteria alive.

A chemical which is bactericidal at a particular concentration, may only be bacteriostatic at a higher dilution.

Decontamination refers to the process of rendering an article or area free of danger from contaminants, including microbial, chemical, radioactive and other hazards.

Agents used in sterilization process can be classified as follow:

Physical Agents Of Sterilization

1. Sunlight
2. Drying
3. Dry heat: flaming, incineration, hot air
4. Moist heat: pasteurization, boiling, steam under normal pressure, steam under pressure.
5. Filtration: candles, asbestos pads, membranes.
6. Radiation
7. Ultrasonic and sonic vibrations

Chemical Agents Used For Sterilization

1. Alcohols: ethyl, isopropyl, trichlorobutanol.
2. Aldehydes: formaldehyde, glutaraldehyde.
3. Dyes
4. Halogens
5. Phenols
6. Surface-active agents
7. Metallic salts
8. Gases: ethylene oxide, formaldehyde, beta propiolactone