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Disinfection

Disinfection. Disinfection. Disinfection. The removal of harmful organisms – (but not usually spores) or the reduction of numbers of organisms to a level where they are not harmful. Cf Sterilisation, Sanitisation and Decontamination. Disinfection.

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Disinfection

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  1. Disinfection

  2. Disinfection

  3. Disinfection The removal of harmful organisms – (but not usually spores) or the reduction of numbers of organisms to a level where they are not harmful. Cf Sterilisation, Sanitisation and Decontamination

  4. Disinfection Antiseptics – prevent growth or action of microorganisms and applied to living tissue Low level disinfectants - Most vegetative bacteria some fungi and some viruses Intermediate level disinfectants – TB Vegetative bacteria most viruses and fungi High level disinfectants - kill all microorganisms but not spores in less than 45min. Sterilants - Disinfectants that kill spores under certain conditions. Decontamination.

  5. Disinfection The preferred method is moist heat – boiling or pasteurisation between 65-80oC or steam at sub-atmospheric pressure. Chemicals may be used: • Where heating is impractical or impossible • where cleaning is inadequate • or for dealing with spills or contamination with body fluids In any case CLEANING is the first step

  6. Chemicals Some points : Gram positives - more sensitive Mycobacteria - relatively resistant Bacterial spores - extremely resistant Enveloped viruses – very sensitive Non enveloped viruses – more resistant. Prions - very resistant

  7. Disinfection The best agent and most enduring is Chlorine 1774 Chlorine discovered (Scheele) 1825 Chlorine used in sanitation. 1843 Used by Oliver Wendell Holmes 1861 Used by Ignaz Semmelweiss 1914-18 Used by Dakin

  8. Disinfectants Alcohols ethanol, isopropanol Aldehydes formaldehyde glutaraldehyde Ampholytes Tego Pine fluids Jeypine Halogens chlorine, iodine (hypochlorites or NaDCC, chlorine dioxide, iodophors)

  9. Disinfectants Phenolics: Black fluids (Jeyes) White fluids (Izal) Clear soluble (Hycolin) Chloroxylenol (Dettol) Hexachlorophane (phisoHex) Anionic and non ionic detergents QAC’s: Benzalkonium chloride (cationic detergents) Cetrimide (Cetavlon) Diguanides : Chlorhexidine (Hibitane)

  10. Disinfection

  11. Disinfectants Antibiotics and Disinfectants Therapeutics In vivo In vitro Act selectively Non-specific Require Metabolic Do not activity. Resistance is Resistance is permanent temporary

  12. Disinfectants Two basic mechanisms : • Solution of lipids from cell membrane by detergents and lipid solvents. • Irreversible alteration of proteins eg by denaturants, oxidants, alkylating agents and sulphydryl agents

  13. Disinfectants – Sites of action

  14. The Ideal disinfectant : Has a broad spectrum of activity. Is bactericidal. Acts rapidly Does not deteriorate in storage. Is persistent and stable. Is not inactivated. Is cheap. Is non corrosive. Is non toxic and leaves no toxic residues. Is easily used. Deodorises. Is colourless and non-staining. Is non flammable. Is soluble. Is odourless. Disinfectants In other words there is no ideal disinfectant!

  15. Disinfectants Factors affecting activity: • Accessibility • Temperature • pH • Concentration

  16. Disinfectants Testing Control or ‘Buying and Selling’ tests must be reproducible. They are for Manufacturers in QC, settling disputes and investigating potentials.

  17. Disinfectants • Stability Test • Capacity Test • Screening Test • Rideal-Walker and Chick Martin Tests (phenolic coefficient is meaningless for a non-phenolic)

  18. Disinfectants The In-use Test – The only User’s test for monitoring performance of an agent. Dilute disinfectant (1ml) in 9ml of diluent. Place ten drops (0.02ml) on a NA plate Incubate at 37 and RT for up to a week. Growth on either plate shows survival of orgs. More than 10 cols from each of 10 drops = failure (= >500 orgs/ml)

  19. Disinfectants Neutralisers for In-Use test : Nutrient Broth Alcohols, Aldehydes, Hypochlorites and phenolics. Nutrient Broth + Tween 80 (3%w/v) Diguanides, hypochlorites+detergent, Iodophors, Phenolic+detergent and QAC’s.

  20. Disinfection Disinfectant policy : • Small Committee ! • Define uses • Eliminate use of chemicals where 1. you aim to sterilise. 2. use of heat is possible 3. they are unnecessary

  21. Disinfection Disinfectant policy (cont’d) • Choose and use according to recommendations of an independent body – not a salesman. • Distribute frequently and in correct dilutions (Preferably by pharmacist) • Instruction and supervision • In-use testing on occasion.

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