1004 disinfection

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Disinfection – A physical or chemical means of killing microorganisms, but not necessarily spores. Disinfectant – A chemical or mixture of chemicals used to kill microorganisms, but not necessarily spores. Disinfectants are usually applied to inanimate surfaces or objects.

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Antiseptic – A substance that inhibits the growth and development of microorganisms without necessarily killing them. Antiseptics are usually applied to body surfaces. Decontamination – Any process for removing and /or killing microorganisms. term is also used for removing or neutralizing hazardous chemicals and radioactive materials.

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Cleaning - the removal of dirt, organic matter and stains which can interfere with the killing action of decontaminants brushing, Vacuuming dry dusting, washing or damp mopping with water containing a soap or detergent.

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Pre cleaning is essential to achieve proper disinfection or sterilization. Must be carried out with care to avoid exposure to infectious agents. Materials chemically compatible with the germicides to be applied later must be used. It is quite common to use the same chemical germicide for precleaning and disinfection.

Chemical germicides:

Chemical germicides

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Many germicides can be harmful to humans or the environment . They should be selected, stored, handled, used and disposed of with care For personal safety, gloves, aprons and eye protection are recommended when preparing dilutions of chemical germicides.

Chlorine :

Chlorine A fast-acting broad-spectrum chemical germicide. Relatively harmless to human tissues, easy to handle, colorless and do not stain Normally sold as bleach, an aqueous solution of sodium hypochlorite (NaOCl), which can be diluted with water.

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Activity is considerably reduced by organic matter (protein). Releases chlorine gas at high temperatures weakening their germicidal potential.

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may last for as long as a week. Daily change of solutions receiving materials with high levels of organic matter several times a day A general all-purpose laboratory disinfectant- 0.1 % available chlorine Biohazardous spillage and in the presence of large amounts of organic matter.- 0.5 %

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To disinfect water for drinking, with a final concentration of 1–2 mg/l (1 – 2 ppm ) available chlorine. Bleach is not recommended as an antiseptic Chlorine gas is highly toxic. Indiscriminate use of bleach, should be avoided.

Preparations of Chlorine:

Preparations of Chlorine Bleaching powder 33% available chlorine Sodium dichloroisocyanurate (NaDCC) Powder or tablets is easy and safe to store. Solid NaDCC can be applied on blood spills or biohazardous liquids and left for at least 10 min before removal.

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Recommended dilutions of chlorine-releasing compounds Compound “CLEAN” CONDITIONS “DIRTY” CONDITIONS Available chlorine required 0.1% 0.5% Sodium hypochlorite (5% available chlorine) 20 ml/l 100 ml/l Calcium hypochlorite (70% available chlorine) 1.4 g/l 7.0 g/l Sodium dichloroisocyanurate (60% available chlorine) 1.7 g/l 8.5 g/l NaDCC tablets (1.5 g available chlorine per tablet 1 tablet / litre 4 tablets / litre Chloramine (25% available Cl) 20 g/l 20 g/l

Iodine and iodophors :

Iodine and iodophors The action similar to that of chlorine, slightly less inhibited by organic matter. Iodine can stain fabrics and environmental surfaces Iodophors and tinctures of iodine are good antiseptics. Povidone-iodine is a reliable and safe surgical scrub and preoperative skin antiseptic . Organic iodine-based products must be stored at 4–10 o C to avoid the growth of potentially harmful bacteria in them.

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Iodine solution, either in water or alcohol applied to the skin’s surface directly before any surgical procedure. It is also extremely effective against many Protozoans . Iodine can be toxic. In proper concentration, iodine does not drastically harm human tissues.


disadvantage The clinical use of tincture of iodine stains tissue and may cause local skin irritation and occasional allergic reactions. Intrinsic contamination with Burkholderia cepacia & Pseudomonas aerogenosa causing pseudobacteraemia and peritonitis

Glutaraldehyde :

Glutaraldehyde Active against vegetative bacteria, spores, fungi and lipid- and nonlipid-containing viruses. It is non-corrosive & faster acting than formaldehyde. However, it takes several hours to kill bacterial spores. (2%) solution need to be “activated” (made alkaline) The activated solution can be reused for 1–4 weeks depending on type and frequency of its use. Solutions should be discarded if they become turbid.


disadvantages Glutaraldehyde is toxic and an irritant to skin and mucous membranes, and contact with it must be avoided. It must be used in a fume-hood or in well-ventilated areas. It is not recommended as a spray or solution for the decontamination of environmental surfaces.


Cidex-OPA O- Phthalaldehyde It requires no activation, Not a known irritant to eyes and nasal passages, Excellent stability over a wide range of pH (pH 3-9), Does not require exposure monitoring, Has a barely perceptible odour OPA show good activity against the Mycobacteria including the Glutaraldehyde-resistant strains

Phenolic compounds :

Phenolic compounds Earliest germicides used for the decontamination of environmental surfaces Active against vegetative bacteria and lipid-containing viruses and fungi Show activity against mycobacteria. Not active against spores Activity against non lipid viruses is variable.


Disadvantages Inactivated by water hardness. Incompatible with cationic detergents Not recommended for use on food contact surfaces and in areas with young children. They may be absorbed by rubber and can also penetrate the skin..


Triclosan Bisphenol Triclosan is common in products for hand-washing. It is active mainly against vegetative bacteria and safe for skin and mucous membranes. In addition to its antibacterial properties, triclosan may have anti-inflammatory activity

Dettol :

Dettol Halophenol – Chloroxynelol Widely used Chloroxylenol is bactericidal, but P. aeruginosa and many molds are highly resistant


Chlorhexidine A cationic bisguanide 4% solution in detergent base Bactericidal for Gram positive & gram neg Effective against HIV Herpes virus and Influenza virus Little affected by blood & other organic materials Inactivated by Soaps & anionic detergents

Alcohols :

Alcohols Ethanol (ethyl alcohol,) and 2-propanol (isopropyl alcohol) have similar disinfectant properties. A solution of 70 to 80 percent is employed. Percentages above 90 and below 50 generally are not as effective, Isopropyl alcohol, is effective up to 99 percent .. they leave no residue on surfaces A 10 minute exposure kill vegetative cells, but not spores.

Alcohols :

Can be used on skin, work surfaces of laboratory benches and biosafety cabinets, and to soak small pieces of surgical instruments. Alcohol-based hand-rubs for the decontamination of lightly soiled hands in situations where proper hand-washing is not possible . Alcohols

Alcohols :

Precautions Alcohols are volatile and flammable and must not be used near open flames. Bottles with alcohol-containing solutions must be clearly labelled to avoid autoclaving. Alcohols

Hydrogen peroxide and Peracids :

Hydrogen peroxide and Peracids Like chlorine, hydrogen peroxide (H 2 O 2 ) and peracids are strong oxidants and can be potent broad-spectrum germicides. They are also safer than chlorine to humans and the environment.

Hydrogen peroxide:

3 % solution is a harmless but very weak antiseptic Primary clinical use is in the cleansing of wounds. Effective disinfectant of inanimate materials, Decontamination of work surfaces of laboratory benches and biosafety cabinets, Hydrogen peroxide

Hydrogen peroxide:

Stronger solutions suitable for disinfecting heat-sensitive medical/dental devices. The use of vaporized hydrogen peroxide or Peracetic acid for the decontamination of heat-sensitive medical/surgical devices requires specialized equipment.- Plasma sterilizer Hydrogen peroxide


Hydrogen peroxide and Peracids can be corrosive to metals such as Aluminium, Copper, Brass and Zinc, Can decolourise fabrics, hair, skin and mucous membranes. Articles treated with them must be thoroughly rinsed before contact with eyes and mucous membranes. They should always be stored away from heat and protected from light disadvantages

surface-active agents:

The surface-active detergent substances can be divided into 3 groups. The anionic compounds soap, sodium and potassium salts of higher fatty acid. The alkyl such as sodium lauryl sulfate and alkylbenesulfonates. surface-active agents

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cationic substances The cationic detergents are equally effective against gram-positive and gram-negative bacteria.

Quaternary ammonium compounds :

Quaternary ammonium compounds Used as mixtures and in combination with other germicides, such as alcohols. Good activity against vegetative bacteria Effect on lipid, enveloped (including HIV and HBV) but not non enveloped viruses Benzalkonium chloride used as antiseptics.

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The germicidal activity considerably reduced by organic matter, water hardness and anionic detergents. Potentially harmful bacteria can grow in quaternary ammonium compound solutions. Owing to low biodegradability, these compounds may also accumulate in the environment. Disadvantages

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Bacteria MTB Spores Fungi Viruses Erhyl alcohol (70 - 90%) + + 0 + +,- Isopropyl alcohol 90% ++ + 0 + +,- Alconol iodide (2%) ++ + +,- + + Formalin (37%) + + ++ + + Cidex 2% ++ + ++ + +

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Bacteria MTB Spores Fungi Viruses Iodine 2 - 5% ++ + +,- + + Iodophores (1%) + + +,- +,- + Merthiolate +,- 0 0 + +,- Phenolic derivatives 1 - 3% + + 0 + +,- Quats ( 1:750 - 1:1000 ) ++ 0 0 + 0

Efficiency of Different Chemical Antimicrobial Agents:

Efficiency of Different Chemical Antimicrobial Agents

Spill clean-up procedure :

Spill clean-up procedure In the event of a spill of infectious or potentially infectious material Wear gloves and protective clothing, Cover the spill with cloth or paper towels to contain it. 3. Pour , 5% bleach solution immediately surrounding area

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4. Apply disinfectant concentrically beginning at the outer margin of the spill area, working toward the centre. 5. After 30 min, clear away the materials. If there is broken glass or other sharps involved, use a dustpan to collect into a puncture-resistant container for disposal.

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Decontamination of skin : The area should be washed thoroughly with soap and water. Detergents or abrasive materials must not be used and care must be taken not to damage the skin. Decontamination of cuts/eyes : These should be irrigated with water, taking care to prevent spread of contamination from one area to another.

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Decontamination of clothing: Contaminated garments should be removed immediately and placed in a container. They should not be removed from the spill location until contamination has been monitored.

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For most organic matter and bacteria clear soluble phenolics, diluted according to the manufacturers’ recommendations For blood or viruses, 1% hypochlorites Hypochlorite solution should not be used in centrifuges. Activated gluteraldehyde (2%) should be used on surfaces for decontamination.

Local environmental decontamination:

Local environmental decontamination Decontamination of the laboratory space, furniture and equipment sodium hypochlorite containing 1 g/l available chlorine Stronger solutions (5 g/l) are recommended when dealing with high-risk situations. For environmental decontamination, formulated solutions containing 3% hydrogen peroxide (H 2 O 2 ) make suitable substitutes for bleach solutions.


Fumigation Rooms and equipment can be decontaminated by fumigation with formaldehyde gas generated by heating paraformaldehyde or boiling formalin. Alternately 150gm KMnO4 and 280 ml Formalin per 1000 cu ft area Fumigation should be conducted at an ambient temperature of at least 21 o C and a relative humidity of 70%.

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After fumigation the area must be ventilated thoroughly before personnel are allowed to enter. Gaseous ammonium bicarbonate can be used to neutralize the formaldehyde.

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Bacterial spores Mycobacteria Non lipid or small viruses (Polio virus, Coxsackie virus Fungi ( Candida spp) Vegitative bacteria (Staph aureus, Pseudomonas, entrococci Lipid or medium size viruses HSV, CMV, RSV, HIV, HBV susceptible resistant sterilant High level Intermediate level Low level

Choice of disinfection:

Choice of disinfection medical devices, equipment, and surgical materials are divided into three general categories Critical items , Semicritical items, Noncritical items

Critical items:

Critical items instruments or objects that are introduced directly into the bloodstream or into other normally sterile areas of the body. surgical instruments, cardiac catheters, implants, pertinent components of the heart-lung oxygenator, blood compartment of a hemodialyzer . Sterility at the time of use is required for these items

Semicritical Items:

Semicritical Items Noninvasive flexible and rigid fiberoptic endoscopes, Endotracheal tubes, Anesthesia breathing circuits Cystoscopes Meticulous physical cleaning followed by an appropriate high-level disinfection

Noncritical items:

Noncritical items Either do not ordinarily touch the patient or touch only intact skin. Crutches, Bedboards, Blood pressure cuffs, and a variety of other medical accessories. These items rarely, if ever, transmit disease. Washing with a detergent may be sufficient.

Level of disinfection obtained:

Level of disinfection obtained Chemical sterilants- High level disinfectant with prolonged exposure time A) 2 – 3.2 % Gluteraldehyde- Endoscopes B) 3 – 25% H 2 O 2 Contact lenses C) Peracetic acid High level disinfectants A, B, C + Chlorine

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Intermediate level Isopropyl alcohol small area surface Phenolics surgical instruments Iodophores medical equipments Low level disinfectants Quats food preparation area & floor

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Put the left over specimen& biological fluids with container in foot operated plastic bucket/bin with disinfectant solution, container should be submerged in the solution. At the end of the day, drain off the disinfectant solution in drain.

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Materials contaminated with higher risk organisms, including any clinical or biological waste of human origin, must be thoroughly decontaminated or sterilised and must also be disposed of as hazardous waste Human and animal tissues, blood or body parts must never be placed in the ordinary garbage stream, even if decontaminated.

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