© IFIC:2008 Cleaning, Disinfection and Sterilisation BASIC CONCEPTS OF INFECTION CONTROL International Federation of Infection Control © IFIC:2008 Workers’ Protection Staff responsible for processing contaminated equipment should: • Receive adequate training • Wear appropriate protection • Gloves • Gowns or aprons, and • Splash protection (mask and goggles, or visor) • Receive adequate immunisations © IFIC:2008 Why decontamination? To make the items safe for use in patients To protect the healthcare worker handling the items © IFIC:2008 Choice of Method The method chosen will depend on the item’s intended use the risk of infection the degree of soilage The decontamination process must not damage the device © IFIC:2008 Single Use Devices that cannot be properly cleaned and decontaminated (e.g., injection needles) must be ‘single use’ disposable and not re-processed © IFIC:2008 Classification of Infection Risk Infection risk from equipment or environment can be classified into three categories High risk (critical items) Intermediate risk (semi-critical items) Low risk (non-critical items) © IFIC:2008 Items that enter sterile tissues, including body cavities and the vascular system e.g., surgical instruments, intrauterine devices, vascular catheters Must be cleaned and sterilised before use High Risk = Critical Items © IFIC:2008 Intermediate Risk = Semi-critical Items Items in contact with intact mucous membranes or broken skin e.g., respiratory equipment, gastrointestinal endoscopes, vaginal instruments, thermometers Require cleaning followed by highlevel disinfection © IFIC:2008 Low Risk = Non-critical Items Items in contact with normal skin Bedpans Blood pressure cuffs Patient furniture Must be cleaned and dried © IFIC:2008 Sensitivity to Disinfection and Sterilisation Enveloped viruses Vegetative bacteria and fungi Fungal spores, non-enveloped viruses Mycobacteria Bacterial spores Prions Harder to kill © IFIC:2008 Expected Reduction Levels for Microorganisms drying 10-1 cleaning with water 10-2 cleaning with detergent 10-3 to 4 disinfection 10-3 to 5 sterilization 10-6 Babb JR, Bradley CR 1995 © IFIC:2008 Cleaning Organic soil must be removed before disinfection and sterilisation Disasssemble instruments soon after use to prevent drying of blood and secretions Processes: Manual with water and neutral detergent Washing machine with water and alkaline detergent Rinse after processing to remove chemicals and soil © IFIC:2008 Disinfection Reduces the number of pathogenic microbes (except bacterial spores) to a level that is not harmful to human health Can be achieved by heat or chemicals © IFIC:2008 Thermal Disinfection Heat is preferable to chemicals Washer (flusher) disinfectors include cleaning 1. Rinsing phase to remove soil 2. Disinfection phase 85o C for 15 min require electricity and water supply Pasteurisation: > 70o C for 30 min in water bath Pre-cleaning necessary © IFIC:2008 Chemical Disinfection Effective chemical disinfectants are intended to be toxic to living cells harmful to the user harmful to the environment if stable expensive Use only when necessary Always read the label and follow instructions ! © IFIC:2008 Procedure herpes Hep B Gram + Gram - mycob Heat 80O C S S S S S Alcohol S S S S S Chlorhexid ine S R S S R Aldehydes S S S S M HClO2 S S S S S Org acids S S S S M Phenols R R S S M Quat S R S R R Acridine S R S R R S= sensitive R= resistant M= moderately resistant © IFIC:2008 Many disinfectants are less effective in carrier tests than in suspensions of organisms Disinfectants Can Encapsulate Infective Microorganisms Mechanical cleaning needed Trapping © IFIC:2008 Chemical Disinfection of Objects Organic acids Acetic acid (household use) Oxidates, therefore corrosive Formaldehyde, glutaraldehyde, etc. Fixating agent Rinsing with water may recontaminate the objects Allergen, carcinogen? © IFIC:2008 Chlorine Bleach HClO2 Effective against bacteria enveloped viruses non-enveloped viruses fungi Bleaching Corrosive Inactivated by organic material © IFIC:2008 Microbiological Monitoring of Disinfection Time-consuming Very difficult to standardize Better to focus on ensuring a validated product is used use in the right concentration © IFIC:2008 Storage Decontaminated items must be protected from contamination or damage during storage © IFIC:2008 How Sterilisation Started Postoperative tetanus • Clostridium tetani Gas gangrene • Clostridium perfringens Spore-forming anaerobic bacilli Very low infective dose Toxin production © IFIC:2008 Sterilisation and Sterility Sterility = the absence of all viable microorganisms including spores Sterilisation = the process by which sterility is achieved © IFIC:2008 Sterility Assurance Level The purpose of any sterilizing treatment is to render an article completely free of any living microorganism THIS CAN NEVER BE PROVED Sterility assurance level - SAL 10-6 The probability of a non-sterile article is less than one in a million articles processed © IFIC:2008 Sterilisation Methods Dry heat Steam Ethylene oxide Formaldehyde steam Radiation Plasma H2O2 Aldehydes in aqueous solution © IFIC:2008 The time in minutes at a particular temperature to reduce the viable population by 1 log10 D-value © IFIC:2008 Dry Sterilisation Heat transport from a gas to cooler objects, usually glassware e.g., 1800C - 2 hours Air is a poor conductor Slow process, high temperature Burns paper, cotton etc Protein contamination prolongs sterilization time © IFIC:2008 Steam Vacuum Autoclave © IFIC:2008 Steam Autoclave Heat is generated only on surfaces where steam can condense The autoclave load must be placed so that steam can reach all packages Leads to degradation of DNA, RNA inactivation of enzymes membrane damage protein coagulation © IFIC:2008 Steam Sterilisation of Textiles Air traps prevent steam penetration if poor prevacuum Condensate absorbed to fibres, risk of recontamination if humid © IFIC:2008 Ethylene Oxide Low cost Risk of cancer Aeration - 3 days necessary Common in low income countries, forbidden in high income countries © IFIC:2008 Plasma H2O2 → free oxygen radicals Interact with enzymes, DNA, RNA, cell membrane © IFIC:2008 Plasma Problems Special packaging materials Poor penetration in narrow lumen Process impaired by rests of salts or proteins and by water High cost of equipment High process cost © IFIC:2008 Process Control Sterilization processes have to be validated and controlled Reduction by 1 000 000 fold must be achieved Presterilization values higher than 106 cannot be reduced to 0! © IFIC:2008 Process Monitoring of Sterilisation Time Temperature Pressure Steam hydration Integrating Process Indicators Autoclave tape only shows if the package has been in an autoclave, not what happened there © IFIC:2008 Packaging Use materials such as paper and/or polymers Can be penetrated by steam and still keep the items sterile during storage Mark packages to identify their contents, date of sterilisation, and steriliser and load number Helps to facilitate recall action and to aid in rotation of supplies © IFIC:2008 Sterilization of Heat-sensitive Objects ETO Formaldehyde/steam Plasma - H2O2 Glutaraldehyde or succinaldehydes Ozone © IFIC:2008 Re-processing Five questions about the device need to be asked about the end status of the reprocessed device: Is it intact? Is it clean? Is it sterile? Is the process cost effective? Who takes the responsibility if anything goes wrong? © IFIC:2008 Key Points I The failure to disinfect or sterilize medical equipment properly may result in infection The level of decontamination required depends upon the intended use of the item Cleaning is essential before high level disinfection or sterilisation Chemical disinfection must be used when required by written policies © IFIC:2008 Key points II Thermal decontamination is safer and more effective than chemical Steam sterilisation is effective only when preceded by cleaning and carefully monitored Staff responsible for processing contaminated devices must be fully trained and wear protective apparel © IFIC:2008 References and Further Reading Infection Control Guidelines. Hand Washing, Cleaning, Disinfection and Sterilisation in Health Care. Canada Comm Dis Report 1198;24S8. www-phac-aspc.gc.ca Sterilisation, Disinfection and Cleaning of Medical Equipment: Guidance on Decontamination from the Microbiology Advisory Committee to the Department of Health (The MAC Manual). www.mhra.gov.uk © IFIC:2008