Sterilization and disinfection

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Information about Sterilization and disinfection
Education

Published on January 3, 2012

Author: sarathy4

Source: authorstream.com

Sterilization and Disinfection : Sterilization and Disinfection P resented b y R.P arthasarathy TERMS AND DEFINITIONS: TERMS AND DEFINITIONS Sterilization The process by which an article, surface or medium is freed of all viable microorganisms either in the vegetative or spore state is known as sterilization. Disinfection The process of destruction of pathogenic microorganisms by direct exposure to chemical and physical agents are called as disinfection . The agents used to achieve these state is called disinfectant . Chemical disinfectants which can be safely applied to skin or mucous membrane and are used to prevent infection by inhibiting the growth of bacteria are called antiseptics . Bactericidal agents and germicides Agents which are able to kill bacteria. Bacteriostatic agents Agents which prevents the multiplication of bacteria ( doesn’t kill). Various Agents In Sterilization : Various Agents In Sterilization PHYSICAL AGENTS CHEMICAL AGENTS Sunlight Alcohols: Ethanol, isopropyl Drying Aldehydes: Formaldehyde, Glutaraldehyde Dry heat : Hot air oven, Incineration, Flaming Dyes Moist heat: Boiling, Pasteurization, tyndallisation, Autoclaving Halogens Filtration Phenolic compounds Radiation Ionizing, Non Ionizing Gases Ethylene oxide, Formaldehyde, beta propiolactone (BPL). Ultrasonic vibration Metallic salts and surface active agents Physical Agents:: Physical Agents: Sunlight Direct sunlight is a natural method of sterilization of water in tanks, rivers and lakes. Direct sunlight has an active germicidal effect due to the combined effect of ultraviolet and heat rays. Drying 4/5 of the bacterial weight is due to water. Therefore drying in air has deleterious effect on many bacteria. This is unreliable method, spores are unaffected by drying. Dry heat Flaming: Inoculating loop or wire, the tip of forceps are held in a Bunsen flame till they become red hot. Incineration: This medthod is used to destroy contaminated cloth, animal carcasses and pathological materials. Physical Agents: cont..: Physical Agents: cont.. Hot air oven This method is applicable to metals, glassware, and some heat-resistant oils and waxes that are immiscible in water. Conditions 171ºc for at least one hour. 160ºc for at least two hour. 121ºc for at least sixteen hour. Moist Heat: Flash autoclaves use 134°C for 3 minutes. Method Uses Comments Water < 100°c (Pasteurization) For sterilization of serum, vaccines and body fluids. 62°c for 15 min. 72°c for 30 sec. Spores are not destroyed. Water at 100°c For sterilization of glassware's, metal and rubber items. Some spores are not destroyed. Arnold steamer: Stream at atmospheric pressure For sterilization of culture media containing gelatin and sugar. Preserves properties of media. Autoclave : Stream below atm pressure For sterilization of culture media and laboratory materials. 121°c at 15 psi for 15-20 minutes. Almost Kills all the bacteria and spores. Physical Agents: cont..: Physical Agents: cont.. Filteration : Filtration helps to remove bacteria from large volumes of fluid, especially fluid containing heat-labile components such as sera, solution of sugars and antibiotics. A pore size of 0.2 m is effective because filters act not only mechanically but by electrostatic adsorption of particles to their surface. The filters are of two types (deep and membrane) Physical Agents: cont..: Physical Agents: cont.. FILTERS DEEP FILTERS Made up of Examples Comments and Uses Candle filters 1.Diatomaceous earth 2.Unglazed porcelain Berkefeld filters Chamberlain filters They are available in different porosity. Mostly used for the purification of drinking water and industrial uses. Asbestos filters Asbestos (magnesium silicate) Seitz and Sterimat filters They have high adsorbing capacity and tend to alkalinize the filtered fluid. These are disposable , single use discs available in different grades. Asbestos is carcinogenic hence its use is discouraged. Sintered glass filters Fusing finely powdered glass particles They are expensive and brittle. They have low absorptive property. MEMBRANE FILTERS Cellulose esters Other polymers They are routinely used for water purification and analysis, sterilization, sterility testing and solutions of parenteral use. Wide range of average pore diameters(APD) are available but 0.2mm size is widely used. Physical Agents: cont..: Physical Agents: cont.. RADIATION Non Ionisizing radiation: Types Produced by Mode of action Uses Comments Low energy (Infrared and ultraviolet rays) UV lamps DNA damage Infrared rays: Sterilization of prepacked items such as syringes and catheters. Ultraviolet rays: Used for disinfecting operation threatres and laboratories. Use of UV light is limited by penetration and hazardous. Ionisizing radiation: High energy ionizing type (Gamma rays and high energy electrons such as X-rays and cosmic rays) Cobalt-60 based instruments DNA damage For the sterilization of antibiotics, hormones and other prepacked disposable items such as catheters, gloves, syringes, infusion sets, oils, animal feeds, etc. They are expensive. They are very effective due to high penetrative power. Physical Agents: cont..: Physical Agents: cont.. Ultrasonic and sonic vibration: High frequency sound waves beyond the sensitivity of human ears are called as ultrasonic waves. They have the property to disrupt the cells but the results have been variable. Gram negative rods are more sensitive to ultrasonic vibration whereas Gram positive cocci , spores of fungi and bacteria are resistant to the vibration. Ultrasonic devices are used in dental. However, most sonic machines are not reliable for routine use. Chemical Agents: cont.. : Chemical Agents: cont.. Properties of Ideal antiseptics or disinfectants should Effective against all microorganisms and have a wide spectrum of activity. Have speedy action. Be effective in presence of organic matter. Be effective in varying pH(acidic and alkaline medium). Be active in presence of organic matter. Be stable. Also compatible with other antiseptics and disinfectants. Have high penetrating power. Not corrode metals. Not cause local irritation or sensitization. Not interfere with healing. Not be toxic if absorbed into circulation. Be cheap and safe. Chemical Agents: cont.. : Chemical Agents: cont.. Factors influencing antiseptics or disinfectants: Time of action. Temperature. Concentration of the substance. pH of the medium. Nature of the organisms. Presence of foreign material. Mode of action Protein coagulation. Disruption of cell membrane. Removal of free sulphydryl groups which is essential for the functioning of the enzymes. Substrate competition. Chemical Agents: cont.. : Chemical Agents: cont.. Alcohols Ethyl alcohol, isopropyl alcohol, and n - propanol exhibit rapid, broad-spectrum antimicrobial activity against vegetative bacteria, viruses, and fungi but are not sporicidal . Activity is optimal when they are diluted to a concentration of 60–90% with water. Protein slows its action whereas 1% mineral acid or alkali enhances the action. Aldehydes Formaldehyde is bactericidal, sporicidal , and virucidal . It is active against the amino group in the protein molecule. Formaldehyde gas is used for sterilizing instruments and heat sensitive catheters and for fumigating wards, sick rooms and laboratories. Glutaraldehyde is used for low-temperature disinfection and sterilization of endoscopes and surgical equipment. It is normally used as a 2% solution to achieve sporicidal activity. PowerPoint Presentation: Dyes Two groups of dyes are there 1.Aniline dyes eg : brilliant green, malachite green, crystal violet Acridine dyes eg : proflavine , acriflavine , euflavine and aminacrine . They are used as skin and wound antiseptics. They are more active against Gram positive organisms than Gram negative organisms. Halogens Iodine is an effective disinfectant that acts by iodinating or oxidizing essential components of the microbial cell. Iodine is rapidly bactericidal, fungicidal, tuberculocidal , virucidal , and sporicidal . 2% iodine in 50% alcohol (tincture), which kills more rapidly and effectively than alcohol alone. Iodophors ( eg , povidone -iodine) are complexes of iodine and a solubilizing agent or carrier, which acts as a reservoir of the active I 2 . The most important types of chlorine-releasing agents are sodium hypochlorite, chlorine dioxide, and sodium dichloroisocyanurate , which are oxidizing agents that destroy the cellular activity of proteins Chemical Agents: cont.. PowerPoint Presentation: Phenolic compounds: The use of phenolic compounds are introduced by the Lister. The mode of action is due to their capacity to disrupt the cell membrane. Phenol(carbolic acid) is a potent protein denaturant and bactericidal agent. It is used as disinfectants for various hospital purposes. Cresol and Lysol are active against a wide range of organisms but they are toxic and corrosive. They are used to disinfect surgical instruments, contaminated materials and floors. Halogenated diphenyl compounds such as hexachlorophene and chlorhexidine . Hexachlorophene is toxic and should be handled with care. Cholrhexidene is nontoxic, hence used as skin antiseptic which is more effective against Gram positive organisms than Gram negative organisms. Chemical Agents: cont.. PowerPoint Presentation: Gases: Ethylene oxide is an inflammable and potentially explosive gas. By mixing with inert gases like CO 2 and N 2 to concentration of 10% its explosive tendency is eliminated. It is an alkylating agent that inactivates microorganisms by replacing labile hydrogen atoms on hydroxyl, carboxy , or sulfhydryl groups, particularly of guanine and adenine in DNA. Under controlled condition it is used to sterilise materials such as glass, artificial heart valves, respirators, lung machines, equipments and clothing. Formaldehyde gas and Betapropiolactone (BPL) are used for fumigation of operation theatres and other rooms. BPL is more efficient than formaldehyde gas. Chemical Agents: cont.. PowerPoint Presentation: Surface active agents These compounds have two regions in their molecular structures, one a water-repelling (hydrophobic) group and the other a water-attracting (hydrophilic) group. They are classified into four groups; anionic, cationic, nonionic and amphoteric. They are mainly used as wetting agents, emulsifiers and detergents. Cationic detergents , particularly the quaternary ammonium compounds (“QACs") such as benzalkonium chloride, acetyl trimethyl ammonium bromide are highly bactericidal. They are effective against Gram + ve organisms than Gram – ve organisms. They are more active in alkaline pH. They are inactive against spores and viruses, tubercle bacilli. Anionnic detergents Eg ; common soap. Amphoteric or ampholytic compounds or tego compounds are active against Gram+ve organisms than Gram – ve organisms. Generally it is not used. Chemical Agents: cont.. PowerPoint Presentation: Metallic salts Salts of mercury, copper and silver are used as disinfectant. Mercuric chloride is highly toxic. Hence organic compounds such as mercurochrome, phenyl mercury nitrate and thiomersal are used as antiseptics(less toxic).Copper salts are used as fungicides. Silver salts in aqueous solution have a limited use. Testing of Disinfectants Because of numerous parameters which influence disinfectant activity, there is no reliable test to determine the efficiency of a disinfectant. However Phenol is used as standard. Chemical Agents: cont.. PowerPoint Presentation: Thank you

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