Sterilization


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Sterilization

An act of destroying all forms of life on and in an object. A substance is sterile, from a microbiological point of view, when it is free of all living microorganisms. Sterilization is used principally to prevent spoilage of food and other substances and to prevent the transmission of diseases by destroying microbes that may cause them in humans and animals. Microorganisms can be killed either by physical agents, such as heat and irradiation, or by chemical substances.

Heat sterilization is the most common method of sterilizing bacteriological media, foods, hospital supplies, and many other substances. Either moist heat (hot water or steam) or dry heat can be employed, depending upon the nature of the substance to be sterilized. Moist heat is also used in pasteurization, which is not considered a true sterilization technique because all microorganisms are not killed; only certain pathogenic organisms and other undesirable bacteria are destroyed. See Pasteurization

Many kinds of radiations are lethal, not only to microorganisms but to other forms of life. These radiations include both high-energy particles as well as portions of the electromagnetic spectrum. See Radiation biology

Filtration sterilization is the physical removal of microorganisms from liquids by filtering through materials having relatively small pores. Sterilization by filtration is employed with liquid that may be destroyed by heat, such as blood serum, enzyme solutions, antibiotics, and some bacteriological media and medium constituents. Examples of such filters are the Berkefeld filter (diatomaceous earth), Pasteur-Chamberland filter (porcelain), Seitz filter (asbestos pad), and the sintered glass filter.

Chemicals are used to sterilize solutions, air, or the surfaces of solids. Such chemicals are called bactericidal substances. In lower concentrations they become bacteriostatic rather than bactericidal; that is, they prevent the growth of bacteria but may not kill them. Other terms having similar meanings are employed. A disinfectant is a chemical that kills the vegetative cells of pathogenic microorganisms but not necessarily the endospores of spore-forming pathogens. An antiseptic is a chemical applied to living tissue that prevents or retards the growth of microorganisms, especially pathogenic bacteria, but which does not necessarily kill them.

The desirable features sought in a chemical sterilizer are toxi-city to microorganisms but nontoxicity to humans and animals, stability, solubility, inability to react with extraneous organic materials, penetrative capacity, detergent capacity, noncorro-siveness, and minimal undesirable staining effects. Rarely does one chemical combine all these desirable features. Among chemicals that have been found useful as sterilizing agents are the phenols, alcohols, chlorine compounds, iodine, heavy metals and metal complexes, dyes, and synthetic detergents, including the quaternary ammonium compounds.

Sterilization

 

(1) The method by which a substance, object, or food product is completely freed of live microorganisms. The most common sterilization techniques are heat sterilization and filtration sterilization; the latter is used with liquids and is characterized by the removal of microbial cells with filters. The vegetative cells of most bacteria, yeasts, and microscopic fungi die at temperatures of 50°-70°C within 30 min, whereas the spores of many bacteria can withstand prolonged boiling. This explains why high temperatures are used in sterilization. The simplest sterilization method is heating metal and glass objects on a flame burner. Hot-air sterilization is conducted in hot-air sterilizers at temperatures of 160°-165°C for two hours (hr). This method is used to sterilize laboratory glassware, metal objects, some powder-like materials, and substances that are not damaged by heating. Moist-heat sterilization is carried out in autoclaves with steam under pressure. Microorganic nutrient mediums are sterilized at 4 atmospheres (atm) and 121°C for 20–30 min or at 0.5 atm and 112°C for 20 min. Surgical instruments, dressings, and sutures and various canned foods are usually sterilized at 1 atm for 30 min. Soil may be sterilized only at 2 atm and 134°C for 2 hr.

Some liquids and solutions cannot be sterilized at high temperatures because the temperatures cause the evaporation or inacti-vation of vitamins and other biologically active compounds, the decomposition of drugs, the caramelization of sugars, and the de-naturation of proteins. Under these conditions, heat is not used, and liquids are passed through bacteriological filters having fine pores. Chemical sterilization is used on solid objects that may be damaged by heat, for example, some plastics and electronic apparatus. Chemical sterilizing agents include gases (ethylene oxide mixed with C02 or methyl bromide), alcohol, and mercuric chloride solutions. Radiation sterilization, with doses of ionizing radiation usually at 3–10 million rads, can also be used on solid objects that may be damaged by heat. The number of microorganisms present in the air of enclosed areas, including operating rooms and plants where antibiotics are packaged, can be reduced by ultraviolet radiation, which is bactericidal.

Sterilization is widely used in microbiological and other scientific research, in medicine, and in the food-processing industry. Spacecraft are sterilized in order to prevent the possible contamination of other planets by microorganisms from earth. Sterility is demonstrated by the complete absence of live microorganisms within an object. For this purpose, liquid or solid nutrient-rich mediums are inoculated to allow for the growth of cells that have been damaged but not completely destroyed.

A. A. IMSHENETSKII

(2) The surgical procedure by which an individual is made incapable of reproduction. Unlike castration, the hormonal regulation of sexual function is maintained.

sterilization

[‚ster·ə·lə′zā·shən]
(microbiology)
An act or process of destroying all forms of microbial life on and in an object.
References in periodicals archive ?
At the end of bioreduction, these colloidal solutions (Alkanna-NP and Pinus-NP) were used for surface sterilization of seeds.
* Sterilization not only kills disease-causing microorganisms but also eliminates the transmissible agents such as bacteria and spores through the use of sterilants such as radiation, chemicals, heat among others, thus limiting the risk of exposure to life-threatening diseases.
Jeff Sauter, director of business development, Steri-Tek, a Fremont, Calif.-based provider of E-beam sterilization and X-Ray irradiation for complex medical devices and sensitive materials.
The book's organization is chronological; early chapters focus on institutionalization, the development of the state's sterilization law, and the definition and construction of "feeble-minded" persons.
"In the present study, this risk was 4.1% at the 1-year follow-up, comparable with that reported in previous studies conducted in real-life conditions in patients who received care in public or private hospitals, and much higher than after laparoscopic sterilization."
With its VPA sterilization process utilized across the globe, REVOX Sterilization Solutions serves both the national and international markets, from Australia and New Zealand to Europe and the United States.
Hahn, a fourth-year resident at Indiana University, Indianapolis, and her colleagues followed these women for up to 3 months post partum and found that, within the group that didn't receive immediate postpartum sterilization, just six women--less than 10%--had received sterilization by the end of the follow-up period.
A common way to track trends and changes in polymer sterilization techniques is to look at the medical sterilization equipment market.
The main purpose of infection control is to reduce the occurrence of infectious diseases via sterilization and disinfection technologies which are the essential components.