Sterilization and Disinfection
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The document focuses on sterilization and disinfection methods essential for allied health science students and nurses, detailing definitions and processes for sterilization, disinfection, and antiseptics. It includes explanations of physical and chemical methods of sterilization, such as heat, filtration, radiation, and various chemical agents, along with their applications and effectiveness. Furthermore, it discusses the classification of medical instruments and the appropriate sterilization procedures required for each category to prevent infections.
Sterilization and Disinfection
- 1. Sterilisation and Disinfection for allied health science students and nurses Dr. I. Kannan Ph.D Associate Professor Department of Microbiology Tagore Medical College and Hospital Chennai – 600127. INDIA Lecture series for Allied Health Sciences students and Nurses
- 2. DEFINITION STERILISATION • The process of freeing an article, surface or medium from microorganisms either in vegetative form or spores. STERILANT The agent capable of sterilising objects.
- 3. DEFINITIONS DISINFECTION • Reducing the number of pathogenic microorganisms to the point where they no longer cause diseases . DISINFECTANTS Agents (mostly chemical) used to disinfect inanimate objects.
- 4. DEFINITION Sepsis: Comes from Greek for decay or putrid. Indicates bacterial contamination. Asepsis: Absence of significant contamination. • Aseptic techniques are used to prevent contamination of surgical instruments, medical personnel, and the patient during surgery. • Aseptic techniques are also used to prevent bacterial contamination in food industry.
- 5. DEFINITION ANTISEPTICS Chemicals applied to living tissue to prevent / inhibit pathogen growth.
- 6. Terminal disinfection • Application of disinfection measures after the patient has been removed, e.g., by death, or has ceased to be a source of infection. • the objective is to prepare the rooms or areas for subsequent occupancy of patients for them to be treated without the risk of acquiring an infection.
- 9. Physical Methods 1) Sunlight 2)Drying 3)HEAT 4)FILTRATION 5)RADIATION 6)Ultrasonic/sonic vibration
- 10. HEAT
- 11. There are methods: • Dry heat • Moist heat
- 13. Mode of action • Denaturation of bacterial protein • Oxidative damage • Toxic effects of elevated levels of electrolytes
- 14. Red heat • Inoculation loop or Wire, the tip of Forceps and spatulas are held in a bunsen flame till they are red hot.
- 15. Flaming • A variation on flaming is to dip the object in 70% ethanol (or a higher concentration) and merely touch the object briefly to the Bunsen burner flame, but not hold it in the gas flame. The ethanol will ignite and burn off in a few seconds.
- 16. Incineration • The infective material is burnt into ashes in the incinerator. • This is an excellent method of destroying materials such as contaminated cloth, animal carcasses and pathological materials.
- 17. Hot air • Dry heat utilizes hot air that is free from water vapour. • Dry-heat destroys microorganisms by causing coagulation of proteins. • It is less penetrating and requires longer exposure than moist heat
- 18. Sterilisation By Dry Heat Hot air oven • Kills by oxidation effects • The hot air oven utilizes dry heat to sterilize articles • Operated between 50oC to 250/300oC. • A holding period of 160oC for 1 hr is desirable. • There is a thermostat controlling the temperature. • Double walled insulation keeps the heat in and conserves energy, Hot Air Oven
- 19. Hot air oven Uses: • To sterilise glasswares • To sterilise Forceps, Scissors, Scalpels, Swabs. • Pharmaceuticals products like Liquid paraffin, dusting powder, fats and grease.
- 20. Sterilisation control • Spores of non-toxigenic strain of Clostridium tetani • Thermocouples • Browne’s tube
- 22. Moist heat sterilization • Kills microorganisms by denaturation and coagulating their proteins. • More penetrating power than dry heat.
- 23. Methods in moist heat sterilisation • Temp below 100oC: “Pasteurisation”, Inspissator. • Temperature at 100oC: Boiling. • Steam at atmospheric pressure: Koch & Arnold’s steamer. • Steam under pressure: Autoclave.
- 24. Pasteurisation • Process of killing of pathogens in the milk but does not sterilize it . • Milk is heated at 63oC for 30 mins. (HOLDER METHOD) • At 72oC for 15-20 Sec. Rapid cooling to 13oC (FLASH PROCESS)
- 25. Inspissation • Sterilizes by heating at 80-85oC for half an hour for 3 successive days • Used to sterilize media such as Lowenstein-Jensen & Loefller’s serum
- 26. Inspissator
- 27. Hot water bath • To inactivate non sporing bacteria for the preparation of vaccines - Special vaccine bath at 60oC for one hour is used • Serum or body fluids containing coagulable proteins can be sterilized by heating for 1 hr at 56oC in a water bath for several successive days.
- 28. Water Bath
- 29. Temperature at 100oc Boiling: Kills vegetative forms of bacterial pathogens. • Hepatitis virus: Can survive up to 30 minutes of boiling. Endospores: Can survive up to 20 hours or more of boiling
- 30. Steam at atmospheric pressure • Steam is generated using a steamer (Koch/ Arnold) • Consists of a Tin cabinet • Has a conical lid to enable the drainage of condensed steam • Perforated tray above ensures materials are surrounded by steam. • For routine sterilization exposure of 90 mins is used
- 31. Steam Sterilizer
- 32. Tyndallisation /Intermittent Sterilization • For media containing sugar and gelatin exposure of 100oC for 20 min for 3 successive days is used • The process is termed as Tyndallisation /Intermittent Sterilization
- 33. Tyndallisation /Intermittent Sterilization • The first exposure kills all the vegetative forms • In the intervals between the heating the remaining spores germinate into vegetative forms which are killed on subsequent heating.
- 34. Steam under pressure - Autoclave • Works on the principle of Steam under pressure • Invented by Charles Chamberland in 1879.
- 35. • Autoclave consists of a vertical or a horizontal cylinder. • One end has an opening which is meant for keeping materials to be sterilised. • The lid is provided with a Pressure gauge, to measure the pressure • A safety valve is present to permit the escape of steam from the chamber
- 36. • Articles to be sterilised are placed in the basket provided • Sterilisation is carried out under pressure (15 lbs) at 121º C for 15 mnts.
- 37. An autoclave
- 38. Sterilisation control • Thermocouple • Bacterial spores- Bacillus stearothermophilus • Autoclave tapes • Chemical indicators-Browne’s tube contains red solution which turns green at 121OC for 15 minutes
- 39. FILTRATION
- 40. Sterilisation by filtration Filtration helps to remove bacteria from heat labile liquids such as sera and solutions of sugar, Antibiotics. To obtain bacteria - free filtrates of clinical sample for virus isolation. Bacterial toxins and bacteriophages can be obtained by passing the culture through filters Filter disc - to concentrate bacteria from liquids e.g. testing water sample for cholera vibrio and typhoid bacilli.
- 41. Types of filters The following filters are used Candle filters Asbestos filters Sintered glass filter Membrane filters
- 42. Candle filters • Widely used for purification of water Two types (a) Unglazed ceramic filter – Chamberland filter and Doulton filter (b) Diatomaceous earth filters – Berkefeld filter and Mandler filter
- 43. CANDLE FILTER
- 44. Asbestos filter • Disposable single use discs Disadvantage: • High adsorbing tendency • Carcinogenic Eg: Seitz filter and Sterimat filter
- 46. Sintered glass filter • Prepared by heat fusing powdered glass particles of graded size • Cleaned easily, brittle, expensive.
- 48. Membrane filters • Made of cellulose esters or other polymers • For sterilisation – 0.22µm pore size • For water analysis – 0.45µm pore size Uses • Water purification & analysis • Sterilization & sterility testing • Preparation of solutions for parenteral use
- 49. MEMBRANE FILTER
- 50. HEPA filters • High-efficiency particulate air (HEPA) filters are used to filter the air flowing into aseptic environments (like operation theatre).
- 51. RADIATION
- 52. Radiation Two types of radiations are used NON –IONISING IONISING
- 53. Non- Ionising radiation: • Infra red rays –Absorbed as heat. –Has low penetrating power –Can be considered as hot air sterilisation –Used in rapid mass sterilisation of prepacked Syringes and catheters
- 54. UV radiation • Ultraviolet light irradiation is useful only for sterilisation of surfaces and some transparent objects. • Action: Denaturation of proteins and interferes in the DNA replication.
- 55. UV radiation • UV irradiation is routinely used to sterilize the interiors of biological safety cabinets between uses and operation theatre, • But is ineffective in shaded areas, including areas under dirt. • It also damages some plastics, such as polystyrene foam if exposed for prolonged periods of time.
- 56. IONISING RADIATIONS • X- rays, gamma rays & cosmic rays. • High penetrative power • Action: lethal to DNA and other biomolecules. • No appreciable increase in the temperature – COLD STERILISATION • Sterilise plastics Syringes, catheters, grease fabrics, metal foils
- 57. Gamma rays • Gamma rays are very penetrating and are commonly used for sterilisation of disposable medical equipment, such as syringes, needles, cannulas and IV sets.
- 58. Ultrasonic and Sonic vibration • High frequency sound – beyond the sensitivity of human ear. • They are known to disrupt the cells. • Not used commonly used due to variable result. • More effective to kill gram negative organism.
- 60. Ideal disinfectant/antiseptic • Have wide spectrum of activity • Be active in presence of organic matter • Effective in acid/alkali media • Have speedy action • Have high penetrating power • Be stable • Be compatible with other disinfectants
- 61. Ideal disinfectant/antiseptic • Not corrode metals • Not cause local irritation or sensitisation • Should not interfere in healing process • Not be toxic • Cheap and should easily available
- 62. Factors that influence the potency of disinfectant • Concentration of substance • Time of action • pH of the media • Temperature • Nature of organism • Presence of extraneous materials
- 63. Chemical methods Chemical agents act by • Protein coagulation • Disruption of the cell membrane • Removal of Sulphydryl groups • Substrate competition
- 64. Alcohols • Ethanol /Isopropyl alcohol are frequently used • Acts by denaturing bacterial proteins • No action on spores except methyl alcohol • Concentration recommended 70% in water • Alcohol-water mixtures are more penetrating than pure alcohols Uses • Disinfection of clinical thermometer. • Disinfection of the skin – Venupuncture
- 65. Aldehydes • Formaldehyde & Glutaraldehyde are frequently used • Active against the amino group in the protein molecule • Formaldehyde is bactericidal, sporicidal & has a lethal effect on viruses. • Glutaraldehyde is effective against Tubercle bacilli, fungi and viruses
- 66. Uses FORMALDEHYDE • To preserve anatomical specimens • Used to prepare vaccines and toxoids • Destroying Anthrax spores in hair and wool • 10% Formalin+0.5% Sodium tetra borate is used to sterilise metal instruments
- 67. Uses GLUTARALDEHYDE • Used to treat corrugated rubber anesthetic tubes, Face masks, Plastic endotracheal tubes, Metal instruments and polythene tubing
- 68. Oxidising agents • Hydrogen peroxide (H2O2) is a typical oxidising agent • hydrogen peroxide is actually not a very effective antiseptic or disinfectant • This is because bacteria and body tissues contain enzymes (catalase) that inactivate hydrogen peroxide • On the other hand, the oxygen released upon inactivation can help oxygenate deep wounds and thus kill strict- anaerobe contaminants
- 69. Dyes Two groups of dyes are used Aniline dyes Acridine dyes
- 70. Aniline dyes • Are Brilliant green, Malachite green & Crystal violet • Lethal effect due to their reaction with the acid groups in the cell • Active against Gram positive bacteria • No activity against tubercle bacilli
- 71. Acridine dyes • Acridine dyes in use are orange in colour • Impair DNA and thus destroy the reproductive capacity of the cell • Effective against Gram positive than Gram negative • Important dyes are Proflavine, Acriflavine,Euflavine
- 72. Halogens • Iodine in aqueous and alcoholic solution has been used widely as a skin disinfectant • Actively bactericidal with moderate against spores • Chlorine and its compounds have been used as disinfectants in water supplies & swimming pools
- 73. Iodine • Iodine is often employed as a tincture or as an iodophor • A tincture is an alcohol solution of a iodine. • Iodine tinctures may be employed as antiseptics
- 74. Iodine • Iodophors are organic compounds that slowly release of iodine • thus increasing penetration while simultaneously steadily supplying iodine over long periods • Betadine and Isodine are examples of iodophors
- 75. Chlorine • Drinking water is commonly disinfected using hypochlorite • Hypochlorite may either be added directly (i.e., in the form of bleach) or created within water by bubbling chlorine gas through the water
- 76. Phenols • Obtained by distillation of coal tar • Phenols are powerful microbicidal substances • Causes cell membrane damage. • Phenolic derivatives have been widely used as disinfectants for various purposes in hospitals • Eg: Lysol, cresol, chlorhexidine
- 77. Uses • First antiseptic discovered and used by Joseph Lister. • Various combinations are used in the control of pyogenic cocci in surgical & neonatal units in hospitals. • Aqueous solutions are used in treatment of wounds
- 78. Gases Ethylene Oxide –Colourless ,Highly penetrating gas with a sweet ethereal smell. –Effective against all types of microorganisms including viruses and spores –Action due to alkylating amino, carboxyl, hydroxyl and sylphydryl groups in protein molecule
- 79. Uses • Specially used for sterilising heart-lung machines,respirators,sutures,dental equipments, books and clothing. • Also used to sterilise Glass, metal and paper surfaces ,plastics, oil,some foods and tobacco.
- 80. Formaldehyde gas • Widely employed for fumigation of operation theatres, wards, sick rooms and laboratories. • Sterilisation of instruments and heat sensitive catheters, clothing, bedding, furnitures , books etc. • It is produced by adding 150 g of Potassium permangnate to 280 ml of formalin in 1000 cu.ft of room volume.
- 81. Beta propiolactone • Used in fumigation • For sterilisation 0.2% BPL is used • Has a rapid biocidal activity • Very effective against viruses
- 82. Surface active agents Substances which reduce the surface tension – Surface active agents
- 83. • Cations are widely used in the form of quaternary ammonium compounds. Eg. Cetrimide. • Markedly bactericidal, active against Gram positive organisms. • No action on spores, tubercle bacilli, viruses
- 84. Metallic salts • The salts of silver, copper and mercury are used as disinfectants. • Act by coagulating proteins • Marked bacteriostatic, weak bactericidal and limited fungicidal activity
- 85. Metallic salts • Silver nitrate has been used to treat the eyes of newborns to kill any Neisseria gonorrhea that may have been acquired during passage down the birth canal • the treatment of ponds with copper sulphate (which is blue in water solution) as an anti-algal • Selenium compounds are effective antifungals
- 86. Checking of disinfectants • Rideal-Walker Test • Chick Martin Test • Kelsey-Sykes Test • In-Use Tests
- 87. Rideal-Walker Test • Suspensions of same quantity of organisms are subjected to different concentration of phenol and disinfectant to be tested. • The dilution of the disinfectant which sterilizes the suspension is divided by corresponding phenol concentration. • This gives phenol coefficient. • The phenol coefficient of 1.0 means that the disinfectant is as effective as phenol.
- 88. Chick Martin test • Modification of Rideal-Walker test. • The disinfectant acts in presence of organic matter.
- 89. Kelsey-Sykes test • This test gives a measure of the capacity of a disinfectant to retain its activity when repeatedly used. • It is also named as capacity test.
- 90. In Use test • The liquid phase of the disinfectant solutions in actual use is examined quantitatively for viable organisms. • Then a ‘use’ dilution is determined.
- 92. Spaulding classification • Critical – Objects which enter normally sterile tissue or the vascular system and require sterilization • Semi‐critical – Objects that contact mucous membranes or non‐intact skin and require high‐level disinfection, which kills all but high‐levels of bacterial spores • Non‐critical – Objects that contact intact skin but not mucous membranes, and require low‐level disinfection
- 93. Processing critical instruments • Penetrate or enter normally sterile tissue or spaces, including the vascular system. Example: Surgical instruments (elevators, bone files, rongeurs, forceps, etc.) • Must be sterilized between uses or used as single use disposable devices
- 94. Processing semi‐critical objects • Contact mucous membranes and non‐intact skin. Example: Mouth mirrors, cheek retractors, handpieces • Must be sterilized or immersed in high‐level disinfectant
- 95. Non‐critical instruments and devices • Contact intact skin. Example: BP cuffs, electrocardiogram (EKG) leads, stethoscopes • Disinfect using a low level disinfectant