What Are Disinfectants

From Wikipedia, the free encyclopedia.

Disinfection is the destruction of pathogenic and other kinds of microorganisms by physical or chemical means. Disinfectants are chemical substances used to destroy viruses and microbes (germs), such as bacteria and fungi, as opposed to an antiseptic which can prevent the growth and reproduction of various microorganisms, but does not destroy them. The ideal disinfectant would offer complete sterilization, without harming other forms of life, be inexpensive, and non-corrosive. Unfortunately ideal disinfectants do not exist. Many disinfectants are only able to partially sterilize. The most resistant pathogens are bacteria spores but some viruses and bacteria are also highly resistant to many disinfectants.

All disinfectants are also, by their very nature, potentially harmful (even toxic) to humans or animals. They should be treated with appropriate care. Most come with safety instructions printed on the packaging, which should be read in full before using the disinfectant. Most modern household disinfectants contain Bitrex, an exceptionally bitter substance designed to discourage ingestion, as an added safety measure. Those that are used in people's homes should never be mixed with other cleaning products as chemical reactions can occur. They are frequently used in hospitals, dental surgeries, kitchens and bathrooms to kill infectious organisms.

The choice of the disinfectant to be used depends on the particular situation. Some disinfectants have a wide spectrum (kill nearly all microorganisms). (In the UK there was a long running advert for Domestos bleach in which it was claimed that "Domestos kills all known germs Dead!"). Others kill a smaller range of disease-causing organisms but are preferred for other properties (they may not be corrosive, and relatively non-toxic to humans).

The disinfecting properties of sunlight (ultra-violet) are powerful. Basic hygiene, rather than total reliance on chemicals, is important in the fight against bacteria, which generally prefer a warm-moist-dark environment. There are arguments for creating or maintaining conditions which are not conducive to bacterial survival and multiplication, rather than attempting to kill them with chemicals. Bacteria have a very rapid multiplication rate, which enables them to 'evolve' rapidly. Should some bacteria survive a chemical attack, they give rise to the next generation. Thus they are able to develop resistance to hostile chemicals. For this reason, some question the wisdom of impregnating cloths, cutting boards and worktops in the home with bactericidal chemicals. Hygiene in is important in prevention of foodborne illness.

A Note On Terminology

Disinfectants destroy vegetative microbes (bacteria, fungi) and viruses on surfaces, medical equipment and other man-made objects. Antiseptics disinfect skin. Antibiotics either kill or interfere with the life cycle of bacteria inside the body. Substances which kill bacteria are said to have a bactericidal effect, while those which interfere with cell growth and reproduction are said to be bacteriostatic. Disinfectants and antiseptics are bactericidal (some disinfectants are bacteriostatic at low concentrations): antibiotics can be either bactericidal or bacteriostatic.

Sanitation refers to killing 99+ % of germs in applicable situations. Sanitisers are compounds that sanitise.

Common Disinfectants

In addition to these methods high-intensity ultraviolet light can be used for disinfecting smooth surfaces, such as dental tools, but not porous materials that are opague to the light such as wood or foam.

Relative Effectiveness of Disfectants

One way to compare disinfectants is to compare how well they do against a known disinfectant and rate them accordingly. Phenol is the standard, and the corresponding rating system is called the "Phenol coefficient". The disinfectant to be tested is compared with phenol on a standard microbe (usually Salmonella typhi or Staphylococcus aureus). Disinfectants that are more effective than phenol have a coefficient > 1. Those that are less effective have a coefficient < 1.

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