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Sterilization+ Disinfection


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Sterilization+ Disinfection

  1. 1. STERILIZATION AND DISINFECTION Dr Kamran Afzal Classified Microbiologist
  2. 2. Terminology <ul><li>Sepsis </li></ul><ul><ul><li>Bacterial presence at a pathogenic level </li></ul></ul><ul><li>Asepsis </li></ul><ul><ul><li>Absence of significant contamination </li></ul></ul><ul><ul><li>Aseptic technique minimizes contamination </li></ul></ul><ul><li>Antisepsis </li></ul><ul><ul><li>Chemical destruction of vegetative pathogens on living tissue </li></ul></ul><ul><li>Sanitization </li></ul><ul><ul><li>Lowering microbial counts on eating and drinking utensils to safe levels </li></ul></ul>
  3. 3. <ul><li>Antiseptics </li></ul><ul><ul><li>Chemicals that kill microorganisms on living skin or mucous membranes </li></ul></ul><ul><li>Bactericidal </li></ul><ul><ul><li>Chemical agents capable of killing bacteria </li></ul></ul><ul><ul><li>Similarly agents that are virucidal, fungicidal or sporicidal are agents capable of killing these organisms </li></ul></ul><ul><li>Bacteriostatic </li></ul><ul><ul><li>Chemical agents that inhibit the growth of bacteria but do not necessarily kill them </li></ul></ul>
  4. 4. Microbial Characteristics and Control Figure 7.11
  5. 5. Antiseptics vs Disinfectants <ul><li>Antiseptics </li></ul><ul><ul><li>Used on skin and mucous membranes to kill microorganisms </li></ul></ul><ul><ul><li>Not for use on inanimate objects </li></ul></ul><ul><li>Disinfectants </li></ul><ul><ul><li>Used to kill microorganisms on inanimate objects </li></ul></ul><ul><ul><li>Not for use on skin or mucous membranes </li></ul></ul>
  6. 6. Cleaning <ul><ul><li>The physical removal of foreign material, e.g., dust, soil, organic material such as blood, secretions, excretions and microorganisms </li></ul></ul><ul><ul><ul><li>It is accomplished with water, detergents and mechanical action </li></ul></ul></ul><ul><ul><ul><li>Pre-requisite for sterilization and disinfection </li></ul></ul></ul><ul><ul><li>The terms “decontamination” and “sanitation” may be used for this process in certain settings, e.g., central service or dietetics </li></ul></ul>
  7. 7. Indications of Decontamination <ul><li>Bed pans </li></ul><ul><ul><li>Salmonella, Shigella, Vibrio cholerae and Clostridia </li></ul></ul><ul><li>Respiratory therapy eqpt </li></ul><ul><ul><li>Sputum -> Active TB </li></ul></ul><ul><li>Blood spills </li></ul><ul><ul><li>HBV, HCV and HIV </li></ul></ul><ul><li>Medical eqpt </li></ul><ul><ul><li>Blood -> HBV, HCV and HIV </li></ul></ul><ul><li>Surgical / Medical Instruments </li></ul><ul><ul><li>Tissues / Fluids -> CJD </li></ul></ul>
  8. 8. Sterilization <ul><li>Freeing of an article from all living organisms, including viruses, bacteria and fungi and their spores </li></ul><ul><li>Uses </li></ul><ul><ul><li>Instruments and materials used in penetration into normally sterile body parts </li></ul></ul><ul><ul><li>Media, reagents and eqpt used in laboratory practices </li></ul></ul>
  9. 9. Methods of Sterilization <ul><li>Heat </li></ul><ul><li>Ionizing Irradiation </li></ul><ul><li>Filtration </li></ul><ul><li>Gases </li></ul><ul><li>Liquids </li></ul>
  10. 10. Sterilisation by Heat Dry heat <ul><li>Dry heat kills by oxidation (slow, uneven penetration) </li></ul><ul><li>Incineration </li></ul><ul><ul><li>1000-1500 0 C, pathological waste, surgical dressings, sharps, needles, other clinical wastes </li></ul></ul><ul><li>Flaming </li></ul><ul><ul><li>Scalpels, neck of flasks </li></ul></ul><ul><li>Red heat </li></ul><ul><ul><li>Inoculating loops, wires </li></ul></ul>
  11. 11. <ul><li>Hot air ovens </li></ul><ul><ul><li>160 0 C for one hour </li></ul></ul><ul><ul><li>Glassware, oily fluids, powder </li></ul></ul><ul><li>Microwave oven </li></ul><ul><ul><li>Not reliable due to variable heat </li></ul></ul>
  12. 12. Moist heat <ul><li>Moist heat </li></ul><ul><ul><li>Kills by protein coagulation (denaturation of enzymes) so requires lower temperatures and shorter times, but the moisture must penetrate the pathogens to be effective </li></ul></ul><ul><li>Boiling </li></ul><ul><ul><li>At 100 0 C at sea level, kills many vegetative cells and viruses within 10 minutes </li></ul></ul>
  13. 13. Moist Heat Sterilization by Moist heat Moist heat at Below 100 0 C Moist heat At 100 0 C Moist heat At above 100 0 C <ul><li>Pasteurization </li></ul><ul><li>Boiling </li></ul><ul><li>Tyndallization </li></ul><ul><li>Autoclave </li></ul>
  14. 14. <ul><li>Pasteurization </li></ul><ul><ul><li>Destroys pathogens ( Mycobacterium tuberculosis , Salmonella typhi , etc.) without altering the flavor of the food—does not sterilize (63 0 C for 30 sec) </li></ul></ul><ul><ul><li>Higher temperature short time pasteurization applies higher heat for a much shorter time (72 0 C for 15 sec) </li></ul></ul><ul><li>UHT treatment </li></ul><ul><ul><li>An ultra-high-temperature, very short duration treatment (140 0 C for 3 sec) is used to sterilize dairy products </li></ul></ul>
  15. 15. <ul><li>Tyndallization </li></ul><ul><li>Intermittent exposure at 100 0 C </li></ul><ul><ul><li>Principle : One exposure kills vegetative organisms, between heatings the spores become vegetative forms which get killed during subsequent heating </li></ul></ul><ul><li>Gelatin media, media containing sugars </li></ul>
  16. 16. <ul><li>Autoclaving </li></ul><ul><li>Steam applied under pressure (121 0 C for 15 min) is the most effective method of moist heat sterilization </li></ul><ul><ul><li>The steam must directly contact the material to be sterilized </li></ul></ul><ul><ul><li>Loading - steaming till desired temp/pressure is achieved - holding time - cooling/ drying </li></ul></ul>
  17. 17. <ul><li>Sterilization times </li></ul><ul><li>Autoclaves </li></ul><ul><ul><li>115 0 C, 10 lb/in 2 for 45 min </li></ul></ul><ul><ul><li>121 0 C, 15 lb/in 2 for 15-20 min </li></ul></ul><ul><ul><li>134 0 C, 30 lb/in 2 for 3 min </li></ul></ul><ul><li>Hot air oven </li></ul><ul><ul><li>160 0 C for 45 min </li></ul></ul><ul><ul><li>170 0 C for 18 min </li></ul></ul><ul><ul><li>180 0 C for 7.5 min </li></ul></ul>
  18. 18. <ul><li>Monitoring of Autoclave </li></ul><ul><ul><li>The thermocouple (physical) </li></ul></ul><ul><ul><li>Browne’s tube (chemical) </li></ul></ul><ul><ul><li>Autoclave tape (chemical) </li></ul></ul><ul><ul><li>Spores of Bacillus stearothermophilus (biological) </li></ul></ul>
  19. 19. Ionizing Irradiation <ul><ul><li>Both β and γ irradiation are employed industrially for sterilization of large-scale pre-packed single use disposable items </li></ul></ul><ul><ul><ul><li>Needles, syringes, latex catheters, surgical gloves </li></ul></ul></ul><ul><ul><ul><li>In food industry to reduce spoilage and remove pathogens </li></ul></ul></ul>
  20. 20. Filtration <ul><ul><li>Removal of bacteria and other larger microorganisms from ‘liquids’ that are liable to be spoiled by heating </li></ul></ul><ul><ul><ul><li>Cellulose membrane filters with pore size of <0.45 µm </li></ul></ul></ul><ul><ul><ul><li>Blood serum, antibiotic solutions </li></ul></ul></ul><ul><ul><ul><li>Removal of protozoal cysts from drinking water, that are not destroyed by chlorination </li></ul></ul></ul><ul><ul><ul><li>Most viruses and mycoplasmas can pass through filter size as low as 0.22 µm </li></ul></ul></ul>
  21. 21. Sterilant gases <ul><ul><li>Ethylene oxide </li></ul></ul><ul><ul><ul><li>Highly penetrative, microbicidal gas </li></ul></ul></ul><ul><ul><ul><li>Used in industry to sterilize plastics and other thermo-labile eqpt </li></ul></ul></ul><ul><ul><ul><li>Catheters, syringes and prosthetic heart valves </li></ul></ul></ul><ul><ul><li>Formaldehyde in combination with steam </li></ul></ul><ul><ul><ul><li>Used in hospitals to reprocess thermo-labile eqpt </li></ul></ul></ul><ul><ul><li>Both processes carry toxic hazards </li></ul></ul>
  22. 22. Failure of Sterilization <ul><li>Improper packing of load - no intimate circulation of steam </li></ul><ul><li>Defects in the autoclave - door seals and valves </li></ul><ul><li>Defects in steam - over heated, impure or supersaturated steam </li></ul><ul><li>Faulty operation of autoclave </li></ul>
  23. 23. Disinfection <ul><li>Removal of some or all of the pathogenic organisms to a level which is deemed no longer harmful to health and safe to handle </li></ul><ul><li>Disinfection does not destroy bacterial spores </li></ul><ul><ul><li>Perfect disinfectant would also offer complete and full sterilization, without harming other forms of life, be inexpensive, and non-corrosive </li></ul></ul>
  24. 24. Methods of Disinfection <ul><li>Heat </li></ul><ul><li>Moist heat </li></ul><ul><li>Dry heat </li></ul><ul><li>UV Radiation </li></ul><ul><li>Gases </li></ul><ul><li>Filtration </li></ul><ul><li>Chemicals </li></ul>
  25. 25. Moist heat <ul><li>Method of first choice </li></ul><ul><li>Leaves no toxic residues </li></ul><ul><li>Washing laundry or eating utensils in water at 70-80 0 C for a few minutes would kill most of the vegetative organisms </li></ul><ul><li>Exposure to boiling water for 20 min – highly effective disinfection, used where sterilization is not available </li></ul>
  26. 26. UV Radiation <ul><li>Low energy, non-ionizing radiation with poor penetrating power that is lethal to microorganisms under optimum conditions </li></ul><ul><li>Air, water, thin films and surfaces such as laboratory safety cabinets </li></ul>
  27. 27. Gases <ul><li>Formaldehyde </li></ul><ul><li>To disinfect hospital rooms or laboratory safety cabinets </li></ul>
  28. 28. Filtration <ul><li>Air </li></ul><ul><ul><li>Supplied to OTs, pharmaceutical clean rooms and transplant centres </li></ul></ul><ul><ul><li>Extracted from laboratories that are handling dangerous pathogens </li></ul></ul><ul><li>A properly installed HEPA (High-Efficiency Particulate Air) filter achieves 99.997% arrestance of particles of 0.5 µm or larger size </li></ul>
  29. 29. Chemicals <ul><li>Factors influencing the performance of chemical disinfectants </li></ul><ul><ul><li>Concentration and stability of agent </li></ul></ul><ul><ul><li>Accessibility of microorganisms </li></ul></ul><ul><ul><li>Temperature and pH </li></ul></ul><ul><ul><li>Presence of organic or other protein (interfering) substances </li></ul></ul>
  30. 30. <ul><li>Alcohols </li></ul><ul><li>Isopropanol, ethanol and industrial methylated spirits have optimum bactericidal activity at a conc. of 70-90% </li></ul><ul><ul><li>Limited activity against mycobacteria and are not sporicidal </li></ul></ul><ul><ul><li>Washed thermometers and trolley tops </li></ul></ul><ul><li>Alcohol-based formulation with chlorhexidine or povidone-iodine are good choices for hand disinfections </li></ul>
  31. 31. <ul><li>Aldehydes </li></ul><ul><li>Glutaraldehyde </li></ul><ul><ul><li>Broad spectrum action against vegetative microorganisms </li></ul></ul><ul><ul><li>Flexible endoscopes that cannot be sterilized or disinfected by heat </li></ul></ul><ul><li>Formaldehyde </li></ul>
  32. 32. <ul><li>Biguanides </li></ul><ul><li>Chlorhexidine </li></ul><ul><ul><li>Skin and mucous membranes </li></ul></ul><ul><ul><li>Less active against Gram-negative bacteria ( Pseudomonas and Proteus species) </li></ul></ul><ul><ul><li>Limited virucidal, tuberculocidal and sporicidal activity </li></ul></ul>
  33. 33. <ul><li>Halogens </li></ul><ul><li>Hypochlorites </li></ul><ul><ul><li>These broad spectrum, inexpensive and chlorine-releasing disinfectants are of choice against viruses such as Hepatitis B and C and HIV viruses </li></ul></ul><ul><ul><li>Bleaching activity </li></ul></ul><ul><ul><li>Table tops and discard pots </li></ul></ul><ul><li>Iodine </li></ul><ul><li>Povidone-iodine </li></ul><ul><ul><li>Skin disinfection and pre-operative preparation of skin </li></ul></ul>
  34. 34. <ul><li>Phenolics </li></ul><ul><li>Chloroxylenols (Dettol and Lysol etc) </li></ul><ul><ul><li>Broad spectrum activity, relatively cheap </li></ul></ul><ul><ul><li>Cleaning and disinfection of surfaces in hospitals and laboratories, used in mops </li></ul></ul>
  35. 35. <ul><li>Oxidizing agents and H 2 O 2 </li></ul><ul><ul><li>Chlorine dioxide and H 2 O 2 have good antimicrobial properties but are corrosive to skin and metals </li></ul></ul><ul><ul><li>H 2 O 2 - Limited application for treatment of wounds </li></ul></ul>
  36. 36. <ul><li>Surface active agents </li></ul><ul><li>Detergents and QACs (Quarternary Ammonium Compounds) </li></ul><ul><li>CPC and Benzalkonium Chloride </li></ul><ul><ul><li>Cleaning dirty wounds, hand washing and skin disinfection </li></ul></ul><ul><ul><li>Limited antimicrobial activity against vegetative and no activity against spore forms </li></ul></ul>
  37. 37. Sterilization and Disinfection Policy <ul><li>The sources (eqpt, skin and environment) for which a choice of process is required </li></ul><ul><li>The processes and products available for sterilization </li></ul><ul><li>The category of process required for each item </li></ul><ul><ul><li>Sterilization: surgical instruments </li></ul></ul><ul><ul><li>Heat disinfection: laundry, crockery, bed pans </li></ul></ul><ul><ul><li>Cleaning: floors, walls and furniture </li></ul></ul><ul><li>The specific products and method to be used for each item of eqpt </li></ul>
  38. 38. Role of Microbiology Department <ul><li>Identifies the pathogens </li></ul><ul><li>Suggestion and monitoring of Antibiotic therapy </li></ul><ul><li>Education on specimen collection and transportation </li></ul><ul><li>Information on common Antibiogram patterns </li></ul><ul><li>Surveillance of the Hospital environment </li></ul><ul><li>Counseling of the infected Hospital staff </li></ul><ul><li>Data on Hospital Infection </li></ul><ul><li>Infection control in hospital </li></ul>
  39. 39. Good Hand Washing Practices Save many Lives Soap, Water and common sense are yet the best antiseptics William Osler
  40. 41. Physical Antimicrobials Used for sterilizing medical supplies DNA damage Radiation, X-rays Line-drying laundry Strong vis. Light Limited penetration DNA damage (thymine dimers) Radiation, UV Used in food preservation (less effective against fungi) Plasmolysis of contaminants Osmotic Pressure, Addition of salt or sugar Bacteriostatic Decreased chemical reaction rate Cold, Refrigeration Used for food & drug preservation; Does not necessarily kill so used for Long-term storage of bacterial cultures Desiccation and low temperature Cold, Lyophilization (also desiccation) Used for heat sensitive liquids Separation of bacteria from liquid (HEPA: from air) Filtration 170°C for 2 hours ; Used for glassware & instrument sterilization Oxidation & Denatures proteins Dry Heat, Hot air oven Used for inoculating loop Incineration of contaminants Dry Heat, Flaming Kills pathogens in food products Denatures proteins Moist Heat, Pasteurization 121°C at 15 p.s.i. for 30 min k ills everything Denatures proteins Moist Heat, Autoclaving Kills vegetative bacterial cells and viruses Endospores survive Denatures proteins Moist Heat, boiling Comments Mechanisms of Action Agent
  41. 42. Chemical Antimicrobials * Type of Disinfectant: H = High level; I = Intermediate level; L = Low level