□ DISINFECTION
A disinfectant or a germicide is an agent used for killing micro¬organisms and their spores which cause diseases. Various disinfectants are shown in the following table.
Disinfectants
Type – Examples
Natural – Sunlight, air.
Physical agents
Dry heat – Burning hot air, hot air oven.
Moist heat – Boiling, autoclaving.
Radiation – Ultraviolet rays, gamma rays.
Chemical agents
Solids – Zinc, bleaching powder, potassium permanganate.
Liquids – Formalin, gluteraldehyde, phenol, cresol, lysol, dettol, savion.
Gases – Formaldehyde, ethylene oxide.
□ COMMON DISINFECTANTS
1. Dettol : when used to clean the skin surface, it is applied in pure form and left uncovered until the skin becomes dry. When used as an antiseptic hand lotion, two to four teaspoonful of dettol is added to 500 ml of water.
2. Savlon : in a dilution of 1:200, it is used for general antiseptic purposes like washing hospital equipment, disinfection of soiled linen, and spraying the patient’s room.
3. Potassium permanganate : it is an oxidizing agent. It is used as a general germicide, for gargles as a 1:60 solution, and for purification of water.
WHAT ARE ANTISEPTICS ?
They are used for preventing the growth of micro-organisms. But they cannot kill microorganisms. Various antiseptics are shown in the following table.
Antiseptic Features
Spirit: It is a 70% solution of alcohol in water. It kills bacteria effectively. It is used for disinfection of the skin, instruments and ampoules of injections. It is not used for disinfection of raw surfaces and wounds because it exposes tissue, aggravates injuries, and removes the coagulum formed that prevents bacterial entry into the wound.
Acriflavine: It is aniline derivative, soluble in water. It is orange in powder form and yellow in 1:1000 aqueous solution. It stains tissues yellow.It has a bacteriostatic and bactericidal action upon a variety of bacteria, especially gram positive bacteria in an alkaline medium.It is used in dressing of the wounds.
Boric Acid: It is available in the form of colourless and odourless crystals or white powder. Its solubility in water is 5% and in glycerin 25%. It is used as solution, dusting powder, or ointment.It is effective for mucosal inflammation such as eczema, burns, impetigo, fungal infections of skin and bed sores.Its solution is also used for mouth wash and irrigation of bladder.
Carbolic acid: It is a hygroscopic and highly corrosive substance. It is used as disinfectant for sharp instruments like scissors and knife blades. It is used topically to cauterize dog bites, snake bites and other small wounds. Gentian violet: It is moderately soluble in water, alcohol and glycerin. Its 1% solution in 10% alcohol is used for superficial pyogenic infection of skin and mucous membranes, chronic and irritant lesions of the skin.
Glycerin: It is a colourless, odourless, hygroscopic, thick liquid. It is used with other substances mainly magnesium sulphate to reduce swelling in inflammation.
Hydrogen peroxide: It is used in cleaning of wounds. It breaks down into nascent (active) oxygen and water. The oxygen bubbles removes tissue debris from inaccessible parts of wounds. It also kills bacteria by oxidation.
Iodine: It is in the form of grayish-black, brittle plate shaped crystals with a metallic luster. Its tincture contains 2% iodine and 2% potassium iodide in alcoholic solution. It is used for disinfection of skin and treatment of wounds.Its 0.5 to 1% aqueous solution is used for application to wounds, 0.1% solution for irrigation, and 2% solution in glycerin for application to mucous membranes.
Iodoform: It is a mixture of iodine, alcohol and potash. It has a penetrating, rather pleasant smell. It is a mild antiseptic. It relieves pain when applied to a raw mucous surface and prevents putrefaction in wounds discharging pus.
Merbromin (Mercurochrome):It is an organic salt of mercury with weak antiseptic action. It is more bacteriostatic and less irritating and less toxic than inorganic salts of mercury.It is used as antiseptic over dressing.
Nitrofurazone:It is used as topical antibacterial agent in the treatment of mixed infections of skin wounds.
Povidone iodine:It is a complex of iodine with polyvinylpyrolidine and is available as 5 and 10% solutions for antiseptic use. It is less painful than tincture of iodine when applied to wounds.
Silver nitrate: It is in the form of colourless crystals freely soluble in water. It is caustic, antiseptic, and astringent.Its sticks are used for chemical cauterization of granulation tissue.Its 1:1000 solution is used for irrigation of bladder.Its 10% solution is used for application to infected oral ulcers.
Sulfur ointment: It contains 10% precipitated sulfur.It is fungicide and parasiticide.It is used for various skin disorders.
□ STERILIZATION
It is the process of destroying all microorganisms. In first aid gauze, cotton wool, syringes, needles, and instruments have to be sterilized before use, so as to prevent wound infection. Various methods of sterilization for different articles are as shown in the following table.
Article – Method
Syringes – Boil for 15 minutes. Autoclaving.
Gauze and cotton – Autoclaving.
Metallic instruments – Boil for 15 minutes. Autoclaving.