Sterilization & Disinfection MIC 101 PDF

Sterilization & Disinfection Course lecturer: Mr Ajoseh, SO  Objectives 1- Define the terms sterilization, disinfectant and antiseptic. 2- Classify the different methods of sterilization (physical and chemical methods). 3- Know and realizes that heat is the most important method of...

Sterilization & Disinfection Course lecturer: Mr Ajoseh, SO  Objectives 1- Define the terms sterilization, disinfectant and antiseptic. 2- Classify the different methods of sterilization (physical and chemical methods). 3- Know and realizes that heat is the most important method of sterilization and its application in medical practice. 5- Know dry heat as applied in hot air oven and moist heat as applied in autoclaves. 7- Know the principles of autoclave function and monitoring methods of sterilization. 8- Know the importance of non heat sterilization methods and their use for sterilization of heat sensitive objects. 9-Know the difference between antiseptics and disinfectants. 10- Classify the disinfectants and antiseptics and know factors affecting their functions. 11- Know different applications for different disinfections and antiseptics.  Definitions of terms Sterilization: complete eradication of all forms of microorganisms, including bacterial spores. Disinfection: killing or removing of harmful vegetative microorganisms. Disinfectant: chemical substance used to achieve disinfection on inanimate surfaces. Antiseptic: chemical substances that can be safely used on living tissues for sanitization.  Methods of Sterilization 1. Physical methods: Heat ( dry heat & moist heat) U.V. Light Ionizing Radiation Filtration 2. Chemical method: (used for heat sensitive equipments) Ethylene Oxide Gluteraldehyde. Sterilization by Physical Method HEAT : Most important should be used whenever possible , types: A-Dry heat at temperature of 160˚C for one hour B- Moist heat eg. Autoclave at 121 or 134 C for 10 or 15 minute  Sterilization by Heat Common methods Dry Heat Dry Heat- kills microorganisms by destroying their oxidative processes. Simplest method is exposing item to be sterilized to the naked flame e.g. Bunsen burner- for sterilizing bacteriological loops, knives, blades. Hot air oven expose items to 160 °C for 1 hour. Has electric element in chamber as source of heat plus a fan to circulate air for even distribution of heat in chamber. Oven without fan is dangerous. Used for items that are lacking water such as: -Metals -Glassware -Ointment / Oils/ Waxes /Powder  Moist Heat Uses hot water. Moist heat kills microorganisms by denaturating proteins. Autoclaving – standard sterilization method in hospitals. The equipment is called Autoclave and it works under the same principle as the pressure cooker where water boils at increased atmosphere pressure i.e. because of increase pressure the boiling point of water is >100 °C. The autoclave is a tough double walled chamber in which air is replaced by pure saturated steam under pressure.  The air in the chamber is evacuated and filled with saturated steam. The chamber is closed tightly the steam keeps on filling into it and the pressure gradually increases. The items to be sterilized get completely surrounded by saturated steam (moist heat) which on contact with the surface of material to be sterilized condenses to release its latent heat of condensation which adds to already raised temperature of steam so that eventually all the microorganisms in what ever form are killed. The usual temperature achieved is 121 °C , exposure time of only 15 mins.  Advantages of Autoclave Temp. > 100 °C therefore spores killed. Condensation of steam generates extra heat. The condensation also allows the steam to penetrate rapidly into porous materials. Note: for all invasive procedures at operating room or clinics, autoclavable equipments should be used. Monitoring of Autoclaves 1. Physical method: use of thermocouple to measure accurately the temperature. 2. Chemical method: it consists of heat sensitive chemical that changes color at the right temperature and exposure time. e.g. a)- Autoclave tape b)- Browne’s tube. 3. Biological method: where a spore- bearing organism is added during the sterilization process and then cultured later to ensure that it has been killed.  Moist heat: Other Applications Pasteurization Used heat at temperatures sufficient to inactivate harmful organism in milk. The temperatures of sterilization is not achieved. Temperature may be 74°C, for 3-5 seconds. ( Flash methods or 62°C for 30 minutes. ( Conventional method ). Boiling – quite common especially in domestic circumstances.  Pasteurization of milk To prevent diseases like : Typhoid fever Brucellosis Tuberculosis Q fever Other physical methods : Radiation U.V. light Has limited sterilizing power because of poor penetration into most materials. Generally used in irradiation of air in certain areas such as operating rooms and tuberculosis labs. Ionizing radiation- e.g. Gamma radiation: has greater energy than U.V. light, therefore more effective. Used mainly in industrial facilities e.g. sterilization of disposable plastic syringes, gloves, specimens containers and Petri dishes.  Other physical methods : Filtration May be done under either negative or positive pressure. Example ; membrane filter made of cellulose acetate. Generally removes most bacteria but viruses and some small bacteria e.g. Chlamydia & Mycoplasma may pass through. Thus filtration does not technically sterilize items but is adequate for circumstances under which is used. Main use: for heat labile substances e.g. sera, antibiotics.  Sterilization by Chemical Methods Useful for heat-sensitive materials e.g. plastics and lensed endoscopes). 1. Ethylene Oxide Chamber Ethylene oxide alkylates DNA molecules and thereby inactivates microorganisms. Ethylene oxide may cause an explosion if used pure so it is mixed with an inert gas.Requires high humidity (50- 60% ).Temperature: 55-60°C and exposure period 4-6 hours. 2. Activated alkaline Glutaraldehyde 2% Immerse the item in the solution for about 20 minutes. If Mycobacterium tuberculosis or spores present then immersion period 2-3 hours.  Chemical Methods Some strong chemical substances may be used to achieve sterilization ( kill spores) e.g. Gluteraldehyde and Ethylene oxide. Used for heat sensitive equipments. Disinfectants/ Disinfection  Disinfectants These are antimicrobial agents that are applied to non-living objects to destroy microorganisms, the process of which is known as disinfection. Disinfectants should generally be distinguished from antibiotics that destroy microorganisms within the body, and from antiseptics, which destroy microorganisms on living tissue. Sanitisers are high level disinfectants that kill over 99.9% of a target microorganism in applicable situations.  Types of disinfectants Alcohols Aldehydes Halogens Oxidising agents Quaternary ammonium compounds Other  Alcohols Alcohols, usually ethanol or isopropanol, are wiped over benches and allowed to evaporate for quick disinfection. Alcohols are more effective combined with water—70% alcohol is more effective than 95% alcohol. Alcohol is not effective against fungal or bacterial spores.  Aldehydes Aldehydes, such as Glutaraldehyde, have a wide microbiocidal activity and are sporocidal and fungicidal. They are partly inactivated by organic matter and have slight residual activity  Halogens Chloramine is used in drinking water treatment instead of chlorine because it produces less disinfection byproducts. Chlorine is used to disinfect swimming pools and is added in small quantities to drinking water to reduce waterborne diseases. Hypochlorites (Sodium hypochlorite), often in the form of common household bleach, are used in the home to disinfect drains and toilets. Other hypochlorites such as calcium hypochlorite are also used, especially as a swimming pool additive. Hypochlorites yield an aqueous solution of hypochlorous acid that is the true disinfectant. Hypobromite solutions are also sometimes used.  Oxidising agents They act by oxidising the cell membrane of microorganisms, which results in a loss of structure and leads to cell lysis and death. Chlorine dioxide is used as an advanced disinfectant for drinking water to reduce waterborne diseases. In certain parts of the world, it has largely replaced chlorine because it forms fewer byproducts. Sodium chlorite, sodium chlorate, and potassium chlorate are used as precursors for generating chlorine dioxide. Hydrogen peroxide is used in hospitals to disinfect surfaces. It is sometimes mixed with colloidal silver. It is often preferred because it causes far fewer allergic reactions than alternative disinfectants. Also used in the food packaging industry to disinfect foil containers. A 3% solution is also used as an antiseptic. When hydrogen peroxide comes into contact with the catalase enzyme in cells it is broken down into water and a hydroxyl free radical It is the damage caused by the oxygen free radical that kills bacteria. However, recent studies have shown hydrogen peroxide to be toxic to growing cells as well as bacteria; its use as an antiseptic is no longer recommended.[citation needed] Ozone is a gas that can be added to water for sanitation.  Acidic Electrolyzed Water is a strong oxidising solution made from the electrolysis of ordinary tap water in the presence of a specific amount of salt, generally sodium chloride. This environmentally-responsible disinfectant is highly efficacious against bacteria, fungus, mold, spores and other micro-organisms, in very short contact times. It may be applied as liquid, fog or ice.  Potassium permanganate (KMnO4) is a red crystalline powder that colours everything it touches and is used to disinfect aquariums. It is also used widely in community swimming pools to disinfect one’s feet before entering the pool. Additionally, it is widely used to disinfect community water ponds and wells in tropical countries, as well as to disinfect the mouth before pulling out teeth. It can be applied to wounds in a dilute solution; potassium permanganate is a very useful disinfectant.  Peracetic acid is a disinfectant produced by reacting hydrogen peroxide with acetic acid. It is broadly effective against microorganisms and is not deactivated by catalase and peroxidase, the enzymes which break down hydrogen peroxide It can be used over a wide temperature range (0-40°C), a wide pH range (3.0-7.5), in clean-in-place (CIP) processes, in hard water conditions, and is not affected by protein residues.  Phenolics Phenolics are the active ingredient in most bottles of "household disinfectant". They are also found in some mouthwashes and in disinfectant soap and handwashes. Phenol is probably the oldest known disinfectant as it was first used by Lister when it was called carbolic acid.  Quaternary ammonium compounds Quaternary ammonium compounds (Quats), such as benzalkonium chloride, are a large group of related compounds. They are effective against bacteria, but not against some species of Pseudomonas bacteria or bacterial spores. Quats are biocides which also kill algae and are used as an additive in large-scale industrial water systems to minimize undesired biological growth. Quaternary ammonium compounds can also be effective disinfectants against enveloped viruses.  Other Dettol is used to disinfect surfaces at home. It kills the majority of bacteria. It is one of the few disinfectants useful against viruses. Virkon is a wide-spectrum disinfectant used in labs. It kills bacteria, viruses, and fungi. It is used as a 1% solution in water and keeps for one week once it is made up. It is expensive but very effective, its pink colour fades as it is used up so it is possible to see at a glance if it is still fresh.  Disinfection a reduction in the number of viable organisms Can be achieved by: Low-temperature steam Boiling water Chemical disinfectants  Low-temperature steam Most bacteria and viruses are killed by exposure to moist heat Usually achieved with dry saturated steam at 73 C for greater than 10 minutes Effective reliable and suitable for instrument with a lumen Unsuitable for heat-sensitive items and instruments Chemical disinfectants Destroys microorganisms by chemical or physicochemical means Different organisms vary in their sensitivity Gram-positive - highly sensitive Gram-negative - relatively resistant Clostridial & mycobacterial species - very resistant Slow viruses - highly resistant  Disinfectants are suitable for heat-sensitive items Less effective than heat Chemicals used include: Clear soluble phenolics Hypochlorites Alcohols Quaternary ammonium compounds  Very few disinfectants and sanitisers can sterilise (the complete elimination of all microorganisms), and those that can depend entirely on their mode of application. Bacterial endospores are most resistant to disinfectants, however, some viruses and bacteria also possess some tolerance.  Factors influencing activity of disinfectants 1. Activity directly proportional to temperature. 2. Directly proportional to concentration up to a point – optimum concentration. After this level no advantage in further increases in concentration.  Factors influencing activity of disinfectants 3. Disinfectants may be inactivated by : Dirt Organic matter : Proteins, Pus, Blood, Mucus and Feces. Non organic: Cork, Hard water and Some plastics. 4. Time : Disinfectants need time to work. 5. Range of Action : Disinfectants not equally effective against the whole spectrum of microbes. e.g. Chlorhexidine less active against Gram negative bacteria than Gram positive cocci. Hypochlorites and Gluteraldehyde are more active against hepatitis viruses than most other disinfectants.  Hospital disinfection methods Article Disinfectant Floors, walls Phenolics fluids 1-2% Surfaces tables Hypochlorite, Alcohol Skin Surgeons’ hands Chlorhexidine, Iodine alcohol Patient skin 70% Alcohol, Iodine Endoscopes Gluteraldehyde 2% (Cidex), subatmospheric steam Thermometers 70% Alcohol Antiseptics  Antiseptics (Greek αντι, against, and σηπτικος, putrefactive) are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. They should generally be distinguished from antibiotics that destroy microorganisms within the body, and from disinfectants, which destroy microorganisms found on non-living objects. Some antiseptics are true germicides, capable of destroying microbes (bacteriocidal), whilst others are bacteriostatic and only prevent or inhibit their growth. Antibacterials are antiseptics that only act against bacteria.  Some common Alcohols antiseptics Quaternary ammonium compounds Boric acid Chlorhexidine Gluconate Hydrogen peroxide Iodine Mercurochrome Octenidine dihydrochloride Phenol (carbolic acid) compounds Sodium chloride Sodium hypochlorite  Important points Any instrument or item used for sterile body site should be sterile. Any instrument or item used for non- sterile body site can be disinfected. Hand washing is the most important to prevent hospital acquired infection.  Practice questions ______ is the killing or removing of harmful vegetative microorganisms. A ______ is a chemical substance used to achieve disinfection on inanimate surfaces. A ______ is a chemical substance that can be safely used on living tissues for sanitization. The two main physical methods of sterilization are heat and ______. The most important method of sterilization is ______ which can be applied as either dry heat or moist heat.  Phenol is also known as ______ acid. ______ ammonium compounds are commonly used as disinfectants. Alcohol is more effective as a disinfectant when combined with ______. Glutaraldehyde is effective against fungi and helps protect against ______. Chlorine and chlorine dioxide are examples of ______ sterilizing agents.  Dry heat sterilization involves exposing items to a temperature of _____°C for one hour. Moist heat sterilization using an _____ achieves temperatures of 121°C for 15 minutes. Sterilization by dry heat can be achieved using a(n) ______. Ethylene oxide and glutaraldehyde are chemical sterilization methods used for items that cannot withstand ______. Pasteurization heats milk to a temperature of _____°C for 3-5 seconds.  Iodine is commonly used as a(n) ______ for skin disinfection before surgery. Hydrogen peroxide is sometimes used as a(n) ______. The gold standard for monitoring autoclave sterilization is the ______ method. The autoclave uses ______ heat for sterilization.  Further reading https://www.microrao.com/micronotes/sterilization.pdf https://cdr.lib.unc.edu/downloads/2f75rf64d https://www.cfsph.iastate.edu/Disinfection/Assets/Disinfection101.pdf https://ksumsc.com/download_center/Archive/1st/ 438/1.%20Foundation%20Block/Female%20Group/Microbiology/5- sterilization%20disinfection%20-updated.pdf https://ksumsc.com/download_center/Archive/1st/437/1.Foundation %20Block/Team%20Work/Microbiology/4-%20Sterilization.pdf https://onlinelibrary.wiley.com/doi/pdf/10.1128/9781555819682.ch1 https://uomustansiriyah.edu.iq/media/lectures/95/95_2022_12_26! 01_00_32_PM.pdf https://www.drugfuture.com/pharmacopoeia/usp35/PDF/0619- 0622%20%20DISINFECTANTS%20AND%20ANTISEPTICS.pdf https://www.umed.wroc.pl/sites/default/files/mikrobiologia/files/ edSTERILIZATION_and_DISINFECTION.pdf