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Quaternary ammonium compounds

Detergents are organic molecules that serve as wetting agents and emulsifiers and are amphipathic in nature and hence solubilize otherwise insoluble residues and are very effective cleansing agents and are different from soaps, which are derived from fats.

Only cationic detergents are effective disinfectants characterized by positively charged quaternary nitrogen and a long hydrophobic aliphatic chain. They disrupt microbial membranes and may also denature proteins. Mostly used as disinfectants for food utensils and small instruments and as skin antiseptics: benzalkonium chloride and cetylpyridinium chloride.

Aldehydes :

Formaldehyde and glutaraldehyde are highly reactive molecules that combine with nucleic acids and proteins and inactivate them, probably by cross-linking and alkylating molecules. Formaldehyde is usually dissolved in water or alcohol before use. A 2% buffered solution of glutaraldehyde is an effective disinfectant and is mostly used to disinfect hospital and laboratory equipments. These are mostly sporicidal and can be used as chemical sterilants.

Hydrogen peroxide:

H2O2 effects are direct and indirect actions of O2 as it forms hydroxyl free radical which is highly toxic and reactive to cell. As an antiseptic, 3% H2O2 serves a variety of needs including skin and wound cleansing, bedsore care and mouth washing. It is especially useful in treating infection by anaerobic bacteria because of the lethal effects of O2 on these forms. When it is applied to a wound, the enzyme catalase in the tissue decomposes the H2O2 into water and free O2. The O2 causes the wound tissues to bubble and the bubbling removes microorganisms mechanically. Also, the sudden release of O2 brings about chemical changes in certain microorganisms, and these changes lead to microbial death.

Acids and alkalis:

Conditions of very low or high pH can destroy or inhibit microbial cells; but they are limited in application due to their corrosive, caustic and hazardous nature. Aqueous solutions of ammonium hydroxide remain a common component of detergents, cleansers and deodorizers. Organic acids are widely used in food preservation because they prevent spore germination and bacterial and fungal growth. Acetic acid (in the form of vinegar) is a pickling agent that inhibits bacterial growth; propionic acid is commonly incorporated into breads and cakes to retard moulds, benzoic acid and sorbic acids are added to beverages, syrups etc to inhibit yeasts.




1. Physical:

a) mechanical (wet cleaning, washing, shaking out, airing)

b) the effect of temperature:

high (ironing, dry and moist hot air, calcination, boiling, burning),

and low (freeze);

c) radiation and ultrasound.

2. Chemical - treatment of the object with disinfectants.

3. Biological (biological filters, composting).

4. Combined (combination of different methods).

Types of antisepsis:

- mechanical (removal from the wound of infected and non-viable tissues);

-physical (hygroscopic dressings, hypertensive solutions, UV, laser);

- chemical (application of chemical substances with antimicrobial action: miramistin, chlorhexidine, alcohol 70%, brilliant green, hydrogen peroxide, alcohol solution of iodine);

-biological (use of antibiotics, bacteriophages, etc.).

Aseptic - a system of preventive measures, a set of measures to prevent the entry of microorganisms from the environment into the tissue (wound), the body cavity under medical and diagnostic manipulations, into sterile medicinal drugs during their manufacture, into research material, nutrient media, microorganism cultures in laboratory studies.

For this purpose, in bacteriological laboratories, make inoculations at the flame of an alcohol lamp, previously ignited bacteriological loop, sterile nutrient media are used for cultivation. Aseptic is achieved by sterilization of surgical instruments and materials, treatment of the hands of the surgeon before the operation, air and objects of the operating room, the surface of the skin of the operating field, observance of certain rules (sterile coat, gloves, mask, exclusion of conversations), by wet cleaning of premises with disinfectants, use of bactericidal lamps etc.


1.Aldehydes (formaldehyde)

2.Guanidine derivatives (chlorhexidine derivatives)

3.Inorganic acids and their salts (boric acid, sodium sulfite)

4.Organic acids, their salts (benzoic acid, salicylic acid, sorbic acid)

5.Mercury compounds (merthiolate, phenylmercury nitrate).

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