Sterilization

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Sterilization

  1. 1. DR.B.V.RAMANA, M.D.,
  2. 2. <ul><li>Microorganisms capable of causing infection are constantly present in the external environment and on the human body. </li></ul><ul><li>Microorganisms are responsible for contamination and infection. </li></ul><ul><li>The aim of sterilisation is to remove or destroy them from materials or from surfaces. </li></ul>
  3. 3. <ul><ul><li>Relative Resistance of Microbial Forms </li></ul></ul>Highest resistance Moderate resistance Least resistance bacterial endospore (Bacillus & Clostridium) protozoan cyst some fungal spores some naked virus vegetative bacteria that have higher resistance ( M. tuberculosis, S.aureus, Pseudomonas) most bacterial vegetative cells ordinary fungal spores & hypae enveloped virus Yeasts Trophozoites
  4. 4. Definitions: <ul><li>Sterilisation : </li></ul><ul><ul><li>It is a process by which an article, surface or medium is made free of all microorganisms either in vegetative or spore form. </li></ul></ul><ul><li>Disinfection : </li></ul><ul><ul><li>Destruction of all pathogens or organisms capable of producing infections but not necessarily spores. </li></ul></ul><ul><ul><li>All organisms may not be killed but the number is reduced to a level that is no longer harmful to health. </li></ul></ul>
  5. 5. <ul><li>Antiseptics : </li></ul><ul><ul><li>Chemical disinfectants which can safely applied to living tissues and are used to prevent infection by inhibiting the growth of microorganisms. </li></ul></ul><ul><li>Asepsis : </li></ul><ul><ul><li>Technique by which the occurrence of infection into an uninfected tissue is prevented. </li></ul></ul>
  6. 6. a suffix indicating that the antimicrobial agent will kill or destroy a certain group of microorganism suffix “ cide ” – meaning to kill viricide – destroys virus fungicide – destroys fungi bactericide – destroys bacteria Suffix “ static/stasis ” – meaning to stand still a suffix indicating that the agent will prevent the growth or multiplication of the type of organism but are not killed outright bacteriostatic - prevents the growth of bacteria fungistatic – prevents the growth of fungi
  7. 7. <ul><li>Uses of sterilisation: </li></ul><ul><ul><li>Sterilisation of materials, instruments used in surgical and diagnostic procedures. </li></ul></ul><ul><ul><li>Sterilisation of Media and reagents used in the microbiology laboratory. </li></ul></ul><ul><ul><li>Food and drug manufacturing to ensure safety from contaminating organisms. </li></ul></ul>
  8. 8. Methods <ul><li>Physical methods </li></ul><ul><li>Chemical methods </li></ul>
  9. 9. <ul><li>Physical methods: </li></ul><ul><ul><ul><li>Sunlight </li></ul></ul></ul><ul><ul><ul><li>Heat </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Dry heat </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Moist heat </li></ul></ul></ul></ul></ul><ul><ul><ul><li>Filtration </li></ul></ul></ul><ul><ul><ul><li>Radiation </li></ul></ul></ul>
  10. 10. <ul><li>Chemical methods: </li></ul><ul><ul><ul><ul><li>Alcohols </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Aldehydes </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Phenols </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Halogens </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Oxidizing agents </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Salts </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Surface active agents </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Dyes </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Vapour phase disinfectants </li></ul></ul></ul></ul>
  11. 11. Physical methods
  12. 12. <ul><li>Sun light: </li></ul><ul><ul><li>Active germicidal effect due to its content of ultraviolet rays . </li></ul></ul><ul><ul><li>Natural method of sterilisation of water in tanks, rivers and lakes. </li></ul></ul>
  13. 13. <ul><li>Heat : </li></ul><ul><ul><li>Most reliable and commonly employed method . </li></ul></ul><ul><ul><li>Two types: </li></ul></ul><ul><ul><ul><ul><ul><li>Dry heat </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Moist heat </li></ul></ul></ul></ul></ul>
  14. 14. <ul><li>Heat : </li></ul><ul><li>Principle: </li></ul><ul><ul><li>Dry heat kills the organism by </li></ul></ul><ul><ul><ul><li>denaturation of the bacterial proteins, </li></ul></ul></ul><ul><ul><ul><li>oxidative damage </li></ul></ul></ul><ul><ul><ul><li>toxic effect of elevated levels of electrolytes . </li></ul></ul></ul>
  15. 15. <ul><li>Heat : </li></ul><ul><li>Principle: </li></ul><ul><ul><li>Moist heat kills the organism by </li></ul></ul><ul><ul><ul><li>denaturation of the bacterial proteins </li></ul></ul></ul><ul><ul><ul><li>coagulation of the bacterial proteins </li></ul></ul></ul>
  16. 16. <ul><li>Heat : </li></ul><ul><li>Factors influencing: </li></ul><ul><ul><ul><li>Nature of heat </li></ul></ul></ul><ul><ul><ul><li>Temperature and duration </li></ul></ul></ul><ul><ul><ul><li>Characteristic of organism and spores </li></ul></ul></ul><ul><ul><ul><li>Type of material </li></ul></ul></ul>
  17. 17. <ul><li>Heat : </li></ul><ul><li>Dry heat: </li></ul><ul><ul><ul><li>Red heat </li></ul></ul></ul><ul><ul><ul><li>Flaming </li></ul></ul></ul><ul><ul><ul><li>Incineration </li></ul></ul></ul><ul><ul><ul><li>Hot air oven </li></ul></ul></ul>
  18. 18. <ul><li>Dry heat: </li></ul><ul><ul><ul><li>Red heat: Materials are held in the flame of a bunsen burner till they become red hot. </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Inoculating wires or loops </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Tips of forceps </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Needles </li></ul></ul></ul></ul></ul>
  19. 19. <ul><li>Dry heat: </li></ul><ul><ul><ul><li>2. Flaming: Materials are passed through the flame of a bunsen burner without allowing them to become red hot. </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Glass slides </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>scalpels </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Mouths of culture tubes </li></ul></ul></ul></ul></ul>
  20. 20. <ul><li>Dry heat: </li></ul><ul><ul><ul><li>3. Incineration: </li></ul></ul></ul><ul><ul><ul><li>Materials are reduced to ashes by burning. </li></ul></ul></ul><ul><ul><ul><li>Instrument used was incinerator. </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Soiled dressings </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Animal carcasses </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Bedding </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Pathological material </li></ul></ul></ul></ul></ul>
  21. 21. <ul><li>Dry heat: </li></ul><ul><ul><ul><li>4. Hot air oven: </li></ul></ul></ul>
  22. 22. <ul><ul><li>Hot air oven: </li></ul></ul><ul><ul><ul><li>Most widely used method </li></ul></ul></ul><ul><ul><ul><li>Electrically heated and fitted with a fan to even distribution of air in the chamber. </li></ul></ul></ul><ul><ul><ul><li>Fitted with a thermostat that maintains the chamber air at a chosen temperature. </li></ul></ul></ul><ul><ul><ul><li>Temperature and time: </li></ul></ul></ul><ul><ul><ul><ul><ul><li>160 C for 2 hours. </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>170 C for 1 hour </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>180 C for 30 minutes. </li></ul></ul></ul></ul></ul>
  23. 23. <ul><ul><ul><li>Uses: </li></ul></ul></ul><ul><ul><ul><ul><li>Sterilisation of </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Glassware like glass syringes, petridishes, pipettes and test tubes. </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Surgical instruments like scalpels, scissors, forceps etc. </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Chemicals like liquid paraffin, fats etc. </li></ul></ul></ul></ul></ul>
  24. 24. <ul><ul><li>Precautions : </li></ul></ul><ul><ul><ul><li>Should not be overloaded </li></ul></ul></ul><ul><ul><ul><li>Arranged in a manner which allows free circulation of air </li></ul></ul></ul><ul><ul><ul><li>Material to be sterilised should be perfectly dry. </li></ul></ul></ul><ul><ul><ul><li>Test tubes, flasks etc. should be fitted with cotton plugs. </li></ul></ul></ul><ul><ul><ul><li>petridishes and pipetts should be wrapped in paper. </li></ul></ul></ul><ul><ul><ul><li>Rubber materials and inflammable materials should not be kept inside. </li></ul></ul></ul><ul><ul><ul><li>The oven must be allowed to cool for two hours before opening, since glass waremay crack by sudden cooling. </li></ul></ul></ul>
  25. 25. <ul><ul><ul><li>Sterilisation controls : </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Spores of Bacillus subtilis subsp. niger </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Thermocouples </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Browne’s tube </li></ul></ul></ul></ul></ul>
  26. 26. <ul><li>Moist heat sterilisation: </li></ul><ul><ul><ul><li>A temperature below 100°C </li></ul></ul></ul><ul><ul><ul><li>A temperature of 100°C </li></ul></ul></ul><ul><ul><ul><li>A temperature above 100°C </li></ul></ul></ul>
  27. 27. <ul><ul><ul><li>A temperature below 100°C </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Pasteurisation of milk </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Inspissation </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Vaccine bath </li></ul></ul></ul></ul></ul>
  28. 28. <ul><ul><li>Pasteurisation of milk </li></ul></ul><ul><ul><ul><li>Two types </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Holder method ( 63°C for 30 minutes) </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Flash method ( 72°C for 20 seconds followed by quickly cooling to 13°C) </li></ul></ul></ul></ul></ul><ul><ul><li>Inspissation: </li></ul></ul><ul><ul><ul><li>Heating at 80-85°C for half an hour daily on three consecutive days </li></ul></ul></ul><ul><ul><ul><li>Serum or egg media are sterilised </li></ul></ul></ul><ul><ul><li>Vaccine bath: </li></ul></ul><ul><ul><ul><li>Heating at 60°C for an hour daily in vaccine bath for several sucessive days. </li></ul></ul></ul><ul><ul><ul><li>Serum or body fluids can be sterilised by heating at 56°C for an hour daily for several sucessive days. </li></ul></ul></ul>
  29. 29. <ul><ul><li>A temperature at 100°C </li></ul></ul><ul><ul><ul><ul><ul><li>Boiling </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Tyndallisation </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Steam sterilisation </li></ul></ul></ul></ul></ul>
  30. 30. <ul><ul><li>Boiling : </li></ul></ul><ul><ul><ul><li>Boiling for 10 – 30 minutes may kill most of vegetative forms but spores with stand boiling. </li></ul></ul></ul><ul><ul><li>Tyndallisation : </li></ul></ul><ul><ul><ul><li>Steam at 100C for 20 minutes on three successive days </li></ul></ul></ul><ul><ul><ul><li>Used for egg , serum and sugar containing media. </li></ul></ul></ul><ul><ul><li>Steam steriliser : </li></ul></ul><ul><ul><ul><li>Steam at 100°C for 90 minutes. </li></ul></ul></ul><ul><ul><ul><li>Used for media which are decomposed at high temperature. </li></ul></ul></ul>
  31. 31. <ul><ul><li>A temperature above 100°C </li></ul></ul><ul><ul><ul><ul><li>Autoclave : </li></ul></ul></ul></ul><ul><ul><ul><ul><li>-Steam above 100 ° C has a better killing power than dry heat. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>-Bacteria are more susceptible to moist heat. </li></ul></ul></ul></ul>
  32. 32. <ul><li>Components of autoclave: </li></ul><ul><ul><li>Consists of vertical or horizontal cylinder of gunmetal or stainless steel. </li></ul></ul><ul><ul><li>Lid is fastened by screw clamps and rendered air tight by an asbestos washer. </li></ul></ul><ul><ul><li>Lid bears a discharge tap for air and steam, a pressure gauge and a safety valve. </li></ul></ul>
  33. 34. <ul><li>Sterilisation conditions: </li></ul><ul><ul><li>Temperature – 121 °C </li></ul></ul><ul><ul><li>Chamber pressure -15 lb per square inch. </li></ul></ul><ul><ul><li>Holding time – 15 minutes </li></ul></ul><ul><ul><li>Others : </li></ul></ul><ul><ul><ul><li>126°C for 10 minutes </li></ul></ul></ul><ul><ul><ul><li>133°C for 3 minutes </li></ul></ul></ul>
  34. 35. <ul><li>Uses : </li></ul><ul><ul><ul><li>Useful for materials which can not withstand high temp. </li></ul></ul></ul><ul><ul><ul><li>To sterilise culture media, rubber material, gowns, dressings, gloves etc. </li></ul></ul></ul>
  35. 36. <ul><li>Sterilisation controls: </li></ul><ul><ul><ul><li>Thermocouples </li></ul></ul></ul><ul><ul><ul><li>Bacterial spores- Bacillus stearothermophilus </li></ul></ul></ul><ul><ul><ul><li>Browne’s tube </li></ul></ul></ul><ul><ul><ul><li>Autoclave tapes </li></ul></ul></ul>
  36. 37. <ul><li>3. Filtration: </li></ul><ul><ul><ul><li>Useful for substances which get damaged by heat. </li></ul></ul></ul><ul><ul><ul><li>To sterilise sera, sugars and antibiotic solutions. </li></ul></ul></ul><ul><ul><ul><li>To obtain bacteria free filtrates of clinical samples. </li></ul></ul></ul><ul><ul><ul><li>Purification of water. </li></ul></ul></ul>
  37. 38. <ul><li>Types of filters: </li></ul><ul><ul><ul><li>Candle filters </li></ul></ul></ul><ul><ul><ul><li>Asbestos disc filters </li></ul></ul></ul><ul><ul><ul><li>Sintered glass filters </li></ul></ul></ul><ul><ul><ul><li>Membrane filters </li></ul></ul></ul><ul><ul><ul><li>Air filters </li></ul></ul></ul><ul><ul><ul><li>Syringe filters </li></ul></ul></ul>
  38. 39. <ul><ul><ul><li>Candle filters </li></ul></ul></ul>
  39. 40. <ul><ul><ul><li>Membrane filters </li></ul></ul></ul>
  40. 41. <ul><li>Radiations : </li></ul><ul><ul><ul><li>Ionising radiations </li></ul></ul></ul><ul><ul><ul><li>Non - Ionising radiations </li></ul></ul></ul>
  41. 42. <ul><ul><li>Ionising radiations: </li></ul></ul><ul><ul><ul><ul><li>X rays </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Gamma rays </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Cosmic rays </li></ul></ul></ul></ul><ul><ul><ul><li>Gamma radiation are commercially used for sterilisation of disposable items. (cold sterilisation) </li></ul></ul></ul>
  42. 43. <ul><li>Non-Ionising radiation: </li></ul><ul><ul><ul><ul><li>Infra red rays </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Ultraviolet (UV) rays </li></ul></ul></ul></ul><ul><ul><li>Infra red is used for rapid mass sterilisation of syringes and catheters. </li></ul></ul><ul><ul><li>Ultraviolet radiation is used for disinfecting enclosed areas such as bacterial laboratory, inoculation hood, laminar flow and operation theatres. </li></ul></ul>
  43. 44. Chemical Methods
  44. 45. <ul><li>A variety of chemical agents are used as antiseptics and disinfectants. </li></ul><ul><li>Factors influencing the potency of a disinfectant: </li></ul><ul><ul><ul><li>Concentration </li></ul></ul></ul><ul><ul><ul><li>Time of action </li></ul></ul></ul><ul><ul><ul><li>pH </li></ul></ul></ul><ul><ul><ul><li>Temperature </li></ul></ul></ul><ul><ul><ul><li>Nature of organism </li></ul></ul></ul><ul><ul><ul><li>Presence of organic matter </li></ul></ul></ul>
  45. 46. <ul><ul><li>High level disinfectants </li></ul></ul><ul><ul><li>Intermediate level disinfectants </li></ul></ul><ul><ul><li>low level disinfectants </li></ul></ul>
  46. 47. <ul><li>High level disinfectants: </li></ul><ul><li>Glutaraldehyde, Hydrogen peroxide, peracitic acid and chlorine compounds. </li></ul><ul><li>Effectiveness may be equal to that of sterilisation. </li></ul><ul><li>Used for: </li></ul><ul><ul><ul><li>Endoscopes </li></ul></ul></ul><ul><ul><ul><li>Cystoscopes </li></ul></ul></ul><ul><ul><ul><li>Surgical instruments with plastic components </li></ul></ul></ul>
  47. 48. <ul><li>Intermediate level disinfectants </li></ul><ul><li>May not effective against spores </li></ul><ul><li>Includes alcohols, iodophores and phenols </li></ul><ul><li>Used for: </li></ul><ul><ul><li>Laryngoscopes </li></ul></ul><ul><ul><li>Fiber optic endoscopes </li></ul></ul>
  48. 49. <ul><li>Low level disinfectants: </li></ul><ul><ul><li>Many organisms can survive on exposure to these disinfectants. </li></ul></ul><ul><ul><li>Used for items which come in contact with the patients but they do not penetrate into tissues. </li></ul></ul><ul><ul><li>Stethoscopes, ECG electrodes etc. </li></ul></ul>
  49. 50. <ul><li>1.Alcohols : </li></ul><ul><ul><li>Ethyl alcohol and Isopropyl alcohol are commonly used. </li></ul></ul><ul><ul><li>Act by denaturing of bacterial proteins. </li></ul></ul><ul><ul><li>No sporicidal and virucidal activity. </li></ul></ul><ul><ul><li>Used as skin antiseptics. </li></ul></ul><ul><ul><li>Isopropyl alcohol is preferred to Ethyl alcohol as it is better fat solvent, more bactericidal and less volatile. </li></ul></ul>
  50. 51. <ul><li>2. Aldehydes: </li></ul><ul><ul><li>Formaldehyde </li></ul></ul><ul><ul><li>Glutaraldehyde </li></ul></ul>
  51. 52. <ul><ul><li>Formaldehyde: </li></ul></ul><ul><ul><li>Bactericidal, sporicidal and virucidal </li></ul></ul><ul><ul><li>Used in both aqueous solution and gaseous forms </li></ul></ul><ul><ul><li>A 10% aqueous solution is routinely used. </li></ul></ul><ul><ul><li>Uses: </li></ul></ul><ul><ul><ul><ul><li>preservation of tissues for pathological examination </li></ul></ul></ul></ul><ul><ul><ul><ul><li>To sterilise bacterial vaccines </li></ul></ul></ul></ul><ul><ul><ul><ul><li>To prepare toxoid from toxin </li></ul></ul></ul></ul><ul><ul><ul><ul><li>For killing of bacterial cultures and suspensions </li></ul></ul></ul></ul><ul><ul><ul><ul><li>For destroying anthrax spores in hair and wool. </li></ul></ul></ul></ul>
  52. 53. <ul><li>Glutaraldehyde : </li></ul><ul><li>Effective against bacteria , fungi and viruses. </li></ul><ul><li>Less toxic and irritant to eyes and skin than formaldehyde </li></ul><ul><li>Used as 2% buffered solution </li></ul><ul><li>Available commercially as CIDEX </li></ul><ul><li>Uses: </li></ul><ul><ul><li>For sterilisation of cystoscopes, endoscopes and bronchoscopes </li></ul></ul><ul><ul><li>For sterilisation of plastic endotracheal tubes, face masks, rubber anesthetic tubes </li></ul></ul>
  53. 54. <ul><li>3.Phenols: </li></ul><ul><li>Lister,the father of antiseptic surgery, first introduced the use of phenol ( Carbolic acid) in surgery (1867). </li></ul><ul><li>Produced by distillation of coal tar between temperatures of 170°C and 270°C. </li></ul><ul><li>Bactericidal action due to cell membrane damage. </li></ul><ul><li>Commonly used Phenol derivatives are </li></ul><ul><ul><ul><ul><li>cresol </li></ul></ul></ul></ul><ul><ul><ul><ul><li>chlorhexidine </li></ul></ul></ul></ul><ul><ul><ul><ul><li>chloroxylenol </li></ul></ul></ul></ul><ul><ul><ul><ul><li>hexachlorophanes </li></ul></ul></ul></ul>
  54. 55. <ul><li>Cresols : </li></ul><ul><li>Lysol is a solution of cresols in soap. </li></ul><ul><li>Active against a wide range of organisms. </li></ul><ul><li>uses: </li></ul><ul><ul><li>For sterilisation of infected glass ware </li></ul></ul><ul><ul><li>Cleaning of floors </li></ul></ul><ul><ul><li>Disinfection of excreta </li></ul></ul>
  55. 56. <ul><li>Chlorhexidine: </li></ul><ul><ul><li>Eg.Salvlon – (Chlorhexidine and cetrimide) </li></ul></ul><ul><ul><li>More active against Gram positive than Gram negative </li></ul></ul><ul><ul><li>Good fungicidal activity. </li></ul></ul><ul><ul><li>No action on spores and little activity against viruses </li></ul></ul>
  56. 57. <ul><li>Chloroxylenol : </li></ul><ul><ul><li>Eg.dettol </li></ul></ul><ul><ul><li>Less toxic and less irritant. </li></ul></ul><ul><ul><li>Readily inactivated by organic matter </li></ul></ul><ul><ul><li>Inactive against pseudomonas. </li></ul></ul>
  57. 58. <ul><li>Hexachlorophane: </li></ul><ul><li>More active against Gram positive than Gram negative bacteria. </li></ul><ul><li>Bacteriostatic at high dilutions. </li></ul><ul><li>Applied on skin as prophylaxis against staphylococcal infections. </li></ul><ul><li>Potentially toxic and should be used with care. </li></ul>
  58. 59. <ul><li>4.Halogens: </li></ul><ul><ul><ul><li>Chlorine </li></ul></ul></ul><ul><ul><ul><li>Iodine </li></ul></ul></ul><ul><ul><li>Commonly used disinfectants </li></ul></ul><ul><ul><li>Bactericidal, sporicidal and virucidal </li></ul></ul>
  59. 60. <ul><li>Chlorine : </li></ul><ul><ul><li>In the form of </li></ul></ul><ul><ul><ul><ul><li>Bleaching powder, </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Sodium hypochlorite </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Chloramine </li></ul></ul></ul></ul><ul><ul><li>Disinfection is due to release of free chlorine. </li></ul></ul><ul><ul><li>Reacts with water to form hypochlorus acid . </li></ul></ul><ul><ul><li>Bactericidal, virucidal, fungicidal and sporicidal. </li></ul></ul><ul><ul><li>Used in water supplies, swimming pools, food and dairy industries . </li></ul></ul>
  60. 61. <ul><li>Iodine : </li></ul><ul><ul><ul><li>Used as skin disinfectant. </li></ul></ul></ul><ul><ul><ul><li>Bactericidal and moderate action on spores. </li></ul></ul></ul><ul><ul><ul><li>Betadine is one example. </li></ul></ul></ul>
  61. 62. <ul><li>5.Oxidising agents: </li></ul><ul><ul><li>Hydrogen peroxide </li></ul></ul><ul><ul><ul><li>Effective at concentration of 3-6% </li></ul></ul></ul><ul><ul><ul><li>Kills spores at 10- 25% </li></ul></ul></ul><ul><ul><ul><li>Used to disinfect </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Contact lenses </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Surgical prostheses </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Plastic implants </li></ul></ul></ul></ul></ul>
  62. 63. <ul><li>6.Salts: </li></ul><ul><ul><ul><li>Salts of heavy metals have toxic effect on bacteria. </li></ul></ul></ul><ul><ul><ul><li>Salts of copper, silver and mercury are used as disinfectants. </li></ul></ul></ul><ul><ul><ul><li>Act by coagulation of bacterial proteins. </li></ul></ul></ul><ul><ul><ul><li>Mercuric chloride, once used as disinfectant is highly toxic. </li></ul></ul></ul><ul><ul><ul><li>Thiomersol and mercurochrome are less toxic </li></ul></ul></ul><ul><ul><ul><li>Copper salts are used as fungicides. </li></ul></ul></ul>
  63. 64. <ul><li>7.Surface active agents: </li></ul><ul><li>Substances which alter energy relationships at interfaces , producing a reduction of surface tension, are known as surface active agents or surfactants. </li></ul><ul><ul><li>Anionic </li></ul></ul><ul><ul><li>cationic </li></ul></ul><ul><ul><li>nonionic </li></ul></ul><ul><ul><li>amphoteric compounds. </li></ul></ul>
  64. 65. <ul><li>The anionic compounds: </li></ul><ul><li>e.g.:- common soaps, </li></ul><ul><li>Have strong detergent but weak antimicrobial properties . </li></ul><ul><li>These agents are most active at acidic pH. </li></ul><ul><li>Effective against Gram positive organisms but are relatively ineffective against Gram negative species. </li></ul>
  65. 66. <ul><li>Cationic surfactants: </li></ul><ul><li>Quaternary ammonium compounds are the most important cationic surfactants. </li></ul><ul><li>These compounds are bactericidal for a wide range of organisms, gram positive species are more susceptible. </li></ul><ul><li>The common cationic compounds are acetyl trimethyl ammonium bromide (cetavalon or cetrimide) and benzalkonium chloride. </li></ul>
  66. 67. <ul><li>Amphoteric compounds: </li></ul><ul><li>known as ‘Tego’ compounds possess detergent properties of anionic and antimicrobial activity of cationic compounds. </li></ul><ul><li>They are active against a wide range of Gram positive and Gram negative organisms and some viruses. </li></ul>
  67. 68. <ul><li>8.Dyes : </li></ul><ul><li>Two groups of dyes have been used extensively as skin and wound antiseptics </li></ul><ul><ul><li>aniline dyes </li></ul></ul><ul><ul><li>acridine dyes </li></ul></ul><ul><li>Both are bacteriostatic in high dilution but have low bactericidal action. </li></ul><ul><li>Aniline dyes include crystal violet, brilliant green and malachite green. </li></ul><ul><li>They are more active against Gram positive bacteria than Gram negative bacteria. </li></ul>
  68. 69. <ul><li>Acridine dyes include acriflavine , euflavine, proflavine and aminacrine. </li></ul><ul><li>They are more active against Gram positive bacteria than Gram negative bacteria. </li></ul><ul><li>Gentian violet and acriflavine are two widely used dyes for skin disinfection especially in Gram positive bacterial infections. </li></ul>
  69. 70. <ul><li>9.Vapour phase disinfectants: </li></ul><ul><ul><ul><li>Formaldehyde gas </li></ul></ul></ul><ul><ul><ul><li>Ethylene oxide </li></ul></ul></ul><ul><ul><ul><li>Betapropiolactone </li></ul></ul></ul>
  70. 71. <ul><li>Formaldehyde gas: </li></ul><ul><li>Used for fumigation of operation theatres, wards and laboratories etc. </li></ul><ul><li>It is generated by adding 150 gm of KMnO4 to 280 ml of formalin for 1000 cu. Feet of room volume. </li></ul><ul><li>The doors should be sealed and left unopened for 48 hours. </li></ul><ul><li>The gas is toxic and irritant when inhaled. </li></ul><ul><li>After completion of sterilisation the irritant vapours are nullified by exposure to ammonia vapour. </li></ul>
  71. 72. <ul><li>Ethylene oxide: </li></ul><ul><li>It is a colourless liquid with a boiling point of 10.7°C. </li></ul><ul><li>Effective against all types of organisms including viruses and spores. </li></ul><ul><li>It has a potential toxicity to human beings, including mutagenicity and carcinogenicity . </li></ul><ul><li>It is highly inflamable. </li></ul><ul><li>Used for sterilising plastic and rubber articles, respirators, heart lung machines, sutures, dental equipments etc. </li></ul>
  72. 73. <ul><li>Betapropiolactone : </li></ul><ul><li>Condensation product of ketane and formaldehyde. </li></ul><ul><li>It has a boiling point of 163°C. </li></ul><ul><li>Used in 0.2%. </li></ul><ul><li>Effective against all types of organisms including viruses. </li></ul><ul><li>More efficient for fumigation than formaldehyde. </li></ul><ul><li>Used for inactivation of vaccines. </li></ul>
  73. 74. Materials Method 1 Inoculating wires and loops Red heat 2 Glass ware- syringes, petridishes, testtubes, flasks etc. Hot –air oven 3 Disposable syringes, and other disposable items Gamma radiation 4 Culture media Autoclaving 5 Culture media containing serum and egg Tyndallisation 6 Toxin , serum, sugar, and antibiotic solutions Filtration 7 Cystoscope and endoscope Glutaraldehyde 8 Infected soiled dressings Incineration 9 Skin Iodine, alcohol 10 Milk Pasteurisation

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