STERILIZATION AND DISINFECTION.pptx

STERILIZATION AND DISINFECTION BY DR. PRASHANT PATIL

1. Sterilization & disinfection Dr Prashant Patil PROFESSOR AND HEAD ORAL MEDICINE AND RADIOLOGY NAVODAYA DENTAL COLLEGE

2. Microorganisms are ubiquitous. They cause contamination, infection and decay. So it is necessary to remove them from materials and areas. This is the objective of sterilization Health care professionals must learn and practice infection control techniques that limits the spread of contagions . violate an epithelial surface Contaminated with patient blood and saliva

3. Definitions Sterilization - The process by which an article , surface or medium is freed of all living micro-organism either in the vegetative or spore state. Disinfection - the process of the destruction or removal of all pathogenic organisms , or organisms capable of giving rise to infection.

4. Disinfectants- A chemical agent used on inanimate objects to kill vegetative microorganisms, viruses and fungi, but not necessarily bacterial endospores .

5. Antisepsis- Prevention of infection usually by inhibiting the growth of bacteria is called antisepsis Antiseptics- Chemical disinfectants which can be safely applied to the living tissues and are used to prevent infection by inhibiting the growth of bacteria

6. History . Semmelweis  introduced the concept of hand washing with lime Florence  Later laid down the principles of proper hygiene and nursing procedures Lister  Introduced the concept of antiseptic surgeries using carbolic acid Louis Pasteur  Put forth the concept of sterilization techniques using hot air oven, autoclave and sterilizers

7. Classification of sterilization methods CHEMICAL AGENTS

8. Physical agents 1.Sunlight : Bactericidal activity. Germicidal activity because of U V rays + heat. Water in tanks, rivers & lakes. Studies have shown that in India, typhoid bacilli exposed to sun on pieces of white drill cloth were killed in 2 hours where as controls kept in dark room were still alive after 6 days.

9. 2.Heat a. Dry heat b. Moist heat FACTORS AFFECTING STERILIZATION BY HEAT Time and temperature Nature of heat Type of material Characteristics of organism No of microorganisms present Heat is the most reliable method of sterilization, and should be the method of choice unless contraindicated

10. Dry heat KILLING EFFECT OF DRY HEAT 4 methods of dry sterilization: Red Heat Flaming Incineration Hot air oven

11. Incineration Infective material is reduced to ashes by burning. Excellent method for destroying materials such as soiled dressings, animal carcasses, bedding & pathological materials .

12. Hot air oven Kills by oxidation effects Operated between 150 o C to 250/300 o C. There is a thermostat controlling the temperature. Double walled insulation keeps the heat in and conserves energy

13. Uses: To sterilize forceps, Scissors, Scalpels, Swabs , glasswares , petridishes , pipettes, test tubes and flasks Pharmaceuticals products like Liquid paraffin, dusting powder, fats and grease.

14. Advantages Relative ease of use Carbon steel instruments and burs do not rust, corrode or lose their temper or cutting edges if they are well dried before processing Rapid cycles are possible at high temperatures A number of time – temperature combinations can be used

15. Disadvantages High temperatures may damage more heat sensitive items such as rubber or plastic items Sterilization cycles are prolonged at lower temperatures Cycles are not automatically timed on some models Inaccurate calibration, lack of attention to proper setting and adding instruments without restarting the timings are common sources of error Moist heat Moist heat

16. Moist heat Protein denaturation Coagulation of protein Action Advantage of steam lies in the latent heat liberated when it condenses on a cooler surface raising the temperature of that surfaces. Steam at atmospheric pressure Steam under pressure

17. Temperature below 100 degree celsius

18. Vaccine bath  vaccine of non sporing bacteria  are sterilized at 60 C for 1 hour. Serum or body fluids containing coagulable protein  sterilised for 1 hour at 56 C Inspissator  80 – 85 C for 30min Lowenstein Jensens and Loeffer’s serum are rendered sterile for 3 successive days in an inspissator

19. Temperature at 100 C (Boiling)  (10 – 30 min) Vegetative bacteria are killed almost at 90 C – 100 C but sporing bacteria require considerable periods of boiling. Boiling is not recommended for surgical instruments. Hard water should not be used 2% NaH CO 3 Hard water soft water   Lid should not be opened during this period.

20. Steam at atmospheric pressure 100 C : Used for sterilization of culture media which may decompose if subjected to increase in temperature. Koch or Arnold steamer is usually used. Steam at normal atmospheric pressure 100 C  90 min. For media containing sugar or gelatin, exposure of 100 C for 20 min for 3 successive days is used – this is known as.

21. Tyndallization or intermittent sterilization : The principle is first exposure kills all gram – ve bacteria and spores present will germinate in favourable medium and are killed in subsequent occasion.

22. Steam under pressure : An autoclave is a device used to sterilize equipment and is supplied by subjecting them to high pressure & saturated steam The name comes from Greek auto- , ultimately meaning self, and Latin clavis meaning key—a self-locking device CHARLES CHAMBERLAND

23. Principle Water boils when its vapor pressure equals that of the surrounding atmosphere When the pressure inside a closed vessel increases, the temperature at which water boils also increases. Saturated steam has greater penetrative power. The large decrease in volume sucks in more steam to the area and the process continues The condensed water ensures moist conditions for killing the microbes present. The energy that is instantly released when steam comes into contact with an object and quickly denatures vital cell proteins

24. Advantages It is the most rapid and effective method for sterilization of cloth, surgical packs, and towel (other methods are not suitable for processing cloth packs). Temperature can be accurately controlled Heating and penetration of the steam is rapid and effective Shortest sterilizing time (faster than dry heat, ethylene oxide and chemical solution) Most effective sterilizing agent Relative availability of office proportioned autoclaving equipment

25. Disadvantages No facility for drying the load after sterilization and before taking it out Method of air discharge is inefficient and it is difficult to decide when the discharge is complete Items sensitive to the elevated temperature cannot be autoclaved . Tendency of moist heat to rust or dull instruments (tends to rust carbon steel instruments) . Cost of autoclave . It takes seven times as much heat to convert boiling water to steam as it takes to cause the same amount of water to boil at room temperature.

26. Dry heat Vs Moist heat Sl. no Properties Dry heat Moist heat 1. Principal antimicrobial effect Oxidizes cell protein Denatures cell proteins 2. Time to achieve sterilization Long Short 3. Equipment complexity and cost Low High 4. Tendency to dull or rust instruments Low High 5. Availability of equipment size for office use Good Good

27. Filtration This is the method used to remove bacteria from heat labile liquids Useful for antibiotic solutions, and carbohydrate solutions used in the preparation of culture media. Various types of filters in use Earthen Ware Candles – Berkfield , Chamberland Asbestos Disc Filters – e.g. Seitz Sintered Glass Filters Membrane Filters

28. Membrane filters These are widely used now-a-days. These are made up of CELLULOSE ESTER The range of pore size in which these are available is 0.05 – 12mm Uses: Water purification and analysis Sterilization Sterility testing Preparations of solutions for parenteral use Isolation of virus & production of bacteria free filtrate.

29. Advantages of filters Sterilization of thermolabile parenteral and ophthalmic solution Sterility testing of pharmaceutical products Clarification of water supplies Microbiological evaluation of water purity Viable counting procedures Determination of virus particle size Sera sterilization Sterilization of antibiotics, vaccines, serum Disadvantage Virus and mycoplasma may pass through filter, so filtered serum is not safe for clinical use. Flow rate decreases as viscosity of the liquid increases.

30. Radiation Ionizing radiation : X rays, gamma rays and cosmic rays are used. Lethal to DNA and other vital constituents of cell Penetrative power is high Uses: plastic items, syringes, swabs, catheters, animal feeds, cardboard, oils, greases, fabrics and metal foils. Non ionizing radiation : Infra red and ultraviolet rays are used. Uses: pre packed items such as syringes and catheters.

31. Ultrasonic and sonic vibration It is high frequency sound waves. They are credited with bactericidal powers Microorganisms vary in their sensitivity to them Causes their destruction As the bubble collapses , alternate high and low pressure areas impinge on microorganism High frequency sound waves cause formation of microscopic bubbles in fluid

32. Chemical agents An ideal antiseptic or disinfectant should: Have wide spectrum of activity Be active in presence of organic matter Be effective in acid as well as alkaline medium Have speedy action Have high penetrating power Be stable Compatible with other antiseptics and disinfectants Not corrode metals Not cause local irritation or sensitization Not interfere with healing Not toxic if absorbed into circulation Be cheap and easily available Be safe and easy to use

33. Main mode of action: Protein coagulation Disruption of cell membrane Removal of free sulpydryl groups for functioning of enzymes Substrate competetion : a compound resembling the essential substrate of enzyme diverts or misleads it leading to death

34. ALCOHOL Most commonly used are ETHYL ALCOHOL and ISOPROPYL ALCOHOL. They act by denaturing bacterial proteins. They are mainly used as skin antiseptics. They have no action on spores and viruses. To be effective, the concentration used in 60% - 70% of water.

35. Formaldehyde It is effective against the amino group in the protein molecule. In aqueous solutions, it is markedly bactericidal, sporicidal and possess lethal effect on viruses. Uses – To preserve anatomical specimens. To sterilize heat sensitive catheters & clean metal instruments. Percentage used in 2% - 5%. Gluteraldehyde Its action is similar to formaldehyde. It is specially effective against tubercle bacilli, fungi and virus. It is used mainly to treat corrugated rubber anesthetic tubes, face masks, plastic endotrachealtubes , metal instruments, respirators ALDEHYDES

36. Dyes Aniline dyes Acridine dyes Both are bacteriostatic in high dilution and are used as skin and wound antiseptics. Aniline dyes has lethal effect on bacteria due to its action with the acid groups in the cell. Acridine dye act by impairing the DNA complex of the organism and thus kill or destroy the reproductive capacity of the cell. Use – in lab as selective agents in culture media

37. Phenols Their lethal effect is due to their capacity to cause cell membrane damage, thus releasing cell contents and causes lysis . Agents are used Carbolic acid – powerful microbicidal substance Lysol & cresols – it is active against wide range of organisms. Various proprietary preparations of phenols are used (e.g.) chlorophenols , chloroxyphenols and their various combinations are used. The commercial 4.8% solution of choloroxylenol is known as dettol .

38. Chlorhexidine ( Hibitane ) – it is a relatively non-toxic skin antiseptic. Mostly active against gram positive organisms and fairly active against gram negative ones. It is effective in the presence of pus or blood.

39. Halogens Mainly used are iodine and chlorine Iodine – it is a skin disinfectant in aqueous solutions and alcoholic solutions and an active bactericidal agent. Moderate action against spores. Normal percentage used is 5%. Chlorine – used mainly in water supplies, swimming pools , food and dairy industries. Most commonly used as hypochlorites . It is markedly bactericidal and active against wide spectrum of viruses.

40. Gases ETHYLENE OXIDE: It is highly lethal to all kinds of microbes including spores and tubercle bacilli. Uses: plastic and rubber articles, blankets and pharmaceuticals products. Ethylene oxide which is a gas at a B.P. of 10.8 degree centigrade destroys organism by alkalization. Time – 10 – 16 hours depending on both the temperature and the concentration of ethylene oxide used.

41. FORMALDEHYDE: used for fumigation of operation theatres and other rooms. Formaldehyde gas is generated by adding 150 grams of potassium nitrate to 280ml formalin for every 1000 cubic feet of room volume. The reaction produces considerable heat, and so heat resistant vessels should be used . BETA PROPIOLACTONE : It has a rapid biocidal action but has carcinogenic activity. For sterilization of biological products 0.2% BPL is used. It kills all micro organisms and is very active against viruses.

42. Surface active agents These are substances which alter energy relationships at interfaces producing a reduction of surface or interfacial tension. They are widely used as wetting agents, detergents and emulsifiers.

43. Classification Anionic (e.g.) common soap Cationic are the most important surface active antibacterial agents. They act by denaturation of proteins. The commonly used are Acetyl trimethyl ammonium bromide ( cetavlon or cetrimide ) Benzalkonium chloride Nonionic Amphoteric They are active against both gram positive and gram negative organisms.

44. OXIDISING AGENTS Hydrogen peroxide: It is used as a biocide for disinfection sterilization and antisepsis. Greater activity is seen against gram positive and gram negative bacteria. It acts as an oxidant by producing hydroxyl free radicals, which attacks essential cell components, including lipids, proteins and DNA. Concentration: it is ranging from 3 – 90 %

45. Waste management Biomedical waste: The United Nations Conference on Environment & Development (UNCED) in 1992 recommended the following measures : Prevent & minimize waste production Reuse or recycle the waste to the extent possible Treat waste by safe & environmentally sound methods Dispose off the final residue by landfill in confined and carefully designed sites Any waste generated during the diagnosis, treatment or immunization of human beings or animals or in research or in production or testing of biologicals

46. Categories of biomedical waste in India Option Waste category Treatment disposal Category 1 Human anatomical waste Incineration/ deep burial Category 2 Animal waste Incineration/ deep burial Category 3 Microbiology & biotechnology waste Autoclaving / microwave / incineration Category 4 Waste sharps Disinfection chemical treatment /autoclaving / microwaving / mutilation/ shredding Category 5 Discarded medicines & cytotoxic drugs Incineration, drug disposal in secured landfills Category 6 Solid waste( from blood , cotton dressing , linen, bedding ) Incineration / autoclaving / microwaving Category 7 Solid waste ( tubings , catheters , IV sets) Disinfection chemical treatment , autoclaving/ microwaving / mutilation/ shredding Category 8 Liquid waste Disinfection chemical treatment & discharge into drains Category 9 Incineration ash Disposal in landfill Category 10 Chemicals used in disinfection Chemical treatment ( discharge & land fill )

47. Colour Type of container Waste category Treatment option Yellow Plastic bag Category 1, 2 and Category 3, 6 Incineration/deep burial Red Disinfected container/Plastic bag Category 3, 6, 7 Autoclaving/Microwaving/ Chemical Treatment Blue/White translucent Plastic bag/punture proof container Category 4, 7 Autoclaving/Microwaving Chemical Treatment and destruction/shredding Black Plastic bag Category 5, 9 and Category 10 (solid) Disposal in secured landfill