disinfection
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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. - PowerPoint PPT PresentationTRANSCRIPT
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
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.
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
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
Disinfection
The best agent and most enduring is Chlorine
1774 Chlorine discovered (Scheele)1825 Chlorine used in sanitation.1843 Used by Oliver Wendell Holmes1861 Used by Ignaz Semmelweiss1914-18 Used by Dakin
Disinfectants
Alcohols ethanol, isopropanol
Aldehydes formaldehyde glutaraldehyde
Ampholytes Tego
Pine fluids Jeypine
Halogens chlorine, iodine (hypochlorites or NaDCC,
chlorine dioxide, iodophors)
Disinfectants
Phenolics: Black fluids (Jeyes)White fluids (Izal)Clear soluble (Hycolin)Chloroxylenol (Dettol)Hexachlorophane (phisoHex)
Anionic and non ionic detergentsQAC’s: Benzalkonium chloride(cationic detergents) Cetrimide (Cetavlon)Diguanides : Chlorhexidine (Hibitane)
Disinfection
Disinfectants
Antibiotics and DisinfectantsTherapeutics
In vivo In vitroAct selectively Non-specificRequire Metabolic Do notactivity.Resistance is Resistance ispermanent temporary
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
Disinfectants – Sites of action
Disinfectants
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.
In other words there is no ideal disinfectant!
Disinfectants
Factors affecting activity:
• Accessibility
• Temperature
• pH
• Concentration
Disinfectants
Testing
Control or ‘Buying and Selling’ tests must be reproducible. They are for Manufacturers in QC, settling disputes and investigating potentials.
Disinfectants
• Stability Test• Capacity Test• Screening Test• Rideal-Walker and Chick Martin Tests (phenolic coefficient is meaningless for a non-
phenolic)
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)
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.
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
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.