Disinfection & Sterilization


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Disinfection & Sterilization

  2. 2. TERMINOLOGIES <ul><li>Sterilization – Destroying all microorganisms o an object/ material including their spores </li></ul><ul><li>Disinfection – Reducing/ eliminating pathogenic micro organisms in/ on a material so that they are no longer a hazard </li></ul><ul><li>Disinfectant – Any substance used for the purpose of disinfection (usually an aqueous chemical solution) </li></ul><ul><li>Antiseptics – Chemical disinfectants which can be safely applied to skin and mucus membrane </li></ul><ul><li>Decontamination – Disinfection, along with inactivation/ removal of toxins as well as living pathogens </li></ul><ul><li>Sanitization – Reduce substantially a microbial population to meet accepted public health standard, especially in relation to food ( also aesthetically pleasing) </li></ul><ul><li>Suffice -cide - Agent that kills microorganisms </li></ul><ul><li>Suffix –static – Substance that prevents growth </li></ul><ul><li>Imp factors – Time, temperature, acidity, species and growth phase of the organism </li></ul>
  3. 3. AGENTS USED IN STERILIZATION… <ul><li>Physical agents </li></ul><ul><li>Sunlight </li></ul><ul><li>Drying </li></ul><ul><li>Dry heat- Flaming, incineration, hot air </li></ul><ul><li>Moist heat – Boiling, pasteurization, Steam under normal pressure, steam under pressure </li></ul><ul><li>Filtration – Candles, asbestos pads, membranes </li></ul><ul><li>Radiation </li></ul><ul><li>Ultrasonic and sonic vibrations </li></ul><ul><li>Cold – Freezing, Drying, UV Rays </li></ul>
  4. 4. AGENTS USED IN STERILIZATION <ul><li>Chemicals </li></ul><ul><li>Alcohols – Ethyl, isopropyl, trichlorobutanol </li></ul><ul><li>Aldehydes – Formaldehydes, gluteraldehydes </li></ul><ul><li>Dyes </li></ul><ul><li>Halogens </li></ul><ul><li>Phenols </li></ul><ul><li>Surface active agents </li></ul><ul><li>Metallic salts </li></ul><ul><li>Gases – Ethylene oxide, formaldehyde, betapropiolactone </li></ul>
  5. 5. FACTORS INFLUECING ACTION OF THE KILLING AGENT <ul><li>Time – necessary for action </li></ul><ul><li>Concentration – of the killing agent </li></ul><ul><li>pH - Optimum acidity of alkalinity for best action </li></ul><ul><li>Temperature – optimum </li></ul><ul><li>Number – of organisms present </li></ul><ul><li>Physical state – of the contaminated material </li></ul><ul><li>Surface area exposed - for action of the agent </li></ul><ul><li>Neutralizers – that antagonize activity of the agent </li></ul><ul><li>Impurities – that dilute the agent </li></ul><ul><li>Inactivation - of the agent by time </li></ul>
  6. 6. PHYSICAL AGENTS <ul><li>Sunlight – </li></ul><ul><ul><li>UV rays & heat rays - Bactericidal in nature </li></ul></ul><ul><li>Drying – Effective for bacteria, but not spores </li></ul><ul><li>Heat – Most reliable method. Causes - </li></ul><ul><ul><li>Protein denaturation & coagulation </li></ul></ul><ul><ul><li>Hydrolysis & breakdown of protein </li></ul></ul><ul><ul><li>Oxidative damage </li></ul></ul><ul><ul><li>Toxic effects of elevated electrolyte levels. </li></ul></ul>
  7. 7. FACTORS INFLUECING ‘THERMAL DEATH TIME’ OF MICRO ORGANISM <ul><ul><li>Nature of heat </li></ul></ul><ul><ul><li>Temperature & time of exposure </li></ul></ul><ul><ul><li>No. of microorganisms present </li></ul></ul><ul><ul><li>Characteristics of organism – species, strain, sporing capacity </li></ul></ul><ul><ul><li>Type of material contaminated </li></ul></ul>
  8. 8. <ul><li>Dry heat </li></ul><ul><li>Flaming – Loop, wire, forceps tips over Bunsen flame till red hot </li></ul><ul><li>Incineration – For disposables </li></ul><ul><li>Hot air oven – 160 degrees for 1 hour (glassware, forceps, scalpels, swabs, dusting powder, liq paraffin) </li></ul><ul><li>Tyndallization – Repeated heating at low temperatures (90 – 100 degrees for 30 mts on 3 sucessive days OR 60 degrees for 1 hr for 5 days) </li></ul><ul><li>Sterilization control – Spores of non toxigenic Cl tetani (1000000), Browne’s tube (green spot) </li></ul>
  9. 9. <ul><li>Moist heat – </li></ul><ul><li>Temp < 100 degree C – Pasteurization of milk - 63 degree C for 30 mts (Holder method) - 72 degree C for 15 – 20 secs ( Flash process), and then cooling quickly (13 degree c or low) </li></ul><ul><li>Temp at 100 degree C – Boiling for 10 – 30 mts aftr immersing in water. Add 2% NaHCO3 </li></ul><ul><li>Steam at atm pressure (100 degree C) – Culture media </li></ul><ul><li>Steam under pressure (Autoclave) – 108 – 147 Degree C at 15 - 30 lb/in square for 12 – 15 mts . Latent heat (524 cals), Penetrative power, moisture </li></ul><ul><li>- Sterilization control – Spores of Bacillus Stereothermophilus </li></ul><ul><li>- Chemical indicators, autoclave tapes, thermocouples </li></ul>
  10. 10. <ul><li>Filtration – Remove bacteria from heat labile liquids – sera, sugars/ antibiotics for culture media </li></ul><ul><li>- For viral isolation, obtain bacterial toxins, concentrate bacteria during sample testing of water </li></ul><ul><li>Types of filters – Candle filters, asbestos filters, sintered glass filters, membrane filters </li></ul>
  11. 11. <ul><li>Radiation </li></ul><ul><li>– Non ionizing ( Infra red – syringes, catheters; UV Rays- entry ways, OTs, labs). </li></ul><ul><li>- Ionizing (Gamma rays, X Rays, Cosmic rays) …cold sterilization.. For plastics, glass, swabs, catheters, animal feed, cardboard, oils, greases, fabrics, metal fabrics. </li></ul><ul><li>Ultrasonic & Sonic vibrations – Not much practical use </li></ul>
  12. 12. CHEMICAL AGENTS <ul><li>Criteria for an effective chemical agent – </li></ul><ul><ul><li>Have wide spectrum of activity </li></ul></ul><ul><ul><li>Be active in the presence of organic matter </li></ul></ul><ul><ul><li>Be effective in acid and alkaline media </li></ul></ul><ul><ul><li>Be stable, have speedy action & high penetrative power </li></ul></ul><ul><ul><li>Be compatible with other antiseptics and disinfectants </li></ul></ul><ul><ul><li>Not corrode metals OR cause local irritation/ sensitization </li></ul></ul><ul><ul><li>Not interfere with healing </li></ul></ul><ul><ul><li>Not be toxic if absorbed into circulation </li></ul></ul><ul><ul><li>Be cheap, safe, easy to use & and easily available </li></ul></ul>
  13. 13. CHEMICAL AGENTS <ul><li>Factors determining potency of chemical agents - </li></ul><ul><ul><li>Concentration of substance </li></ul></ul><ul><ul><li>Time of action </li></ul></ul><ul><ul><li>pH of the medium </li></ul></ul><ul><ul><li>Temperature </li></ul></ul><ul><ul><li>Nature of organisms </li></ul></ul><ul><ul><li>Presence of extraneous material </li></ul></ul><ul><li>Mode of action of chemical agents- </li></ul><ul><ul><li>Protein coagulation </li></ul></ul><ul><ul><li>Disruption of cell membrane </li></ul></ul><ul><ul><li>Interference with enzyme functions </li></ul></ul><ul><ul><li>Substrate competition (misleading enzymes) </li></ul></ul>
  14. 14. CHEMICAL AGENTS <ul><li>Alcohols – Methyl alcohol, Ethanol, Isopropyl alcohol (60 – 70% in water) – for Skin, clinical thermometers, cabinets, incubators </li></ul><ul><li>Aldehydes – Formaldehyde - To preserve anatomical specimen, sterilizing incubators and heat sensitive catheters, clothing bedding, furniture; fumigation </li></ul><ul><li>Gluteraldehyde – Effective against Tubercle bacilli, fungi and viruses. Also for plastics, rubbers and metals </li></ul><ul><li>Dyes – Aniline and acridine dyes for skin and wound antisepsis. Bacteriostatic, effective against Gm +ve. Brilliant green, crystal violet, acriflavine, proflavine </li></ul><ul><li>Halogens – Aqueous solutions of iodine, Chlorine </li></ul><ul><li>Phenols – (Carbolic acids) – Microbicidal. Lysol, cresol, Iteol, hexachlorophane, Chlorhexidine </li></ul>
  15. 15. CHEMICAL AGENTS <ul><li>Gases – </li></ul><ul><li>Ethylene oxide –For heart- lung machine, respirator, sutures, dental equipment, books & clothing (explosive in nature) </li></ul><ul><li>Formaldehyde – Fumigation (150 gms KMNO4 + 280 ml Formalin/ 1000 cu ft for 48 hrs) </li></ul><ul><li>Betapropiolactone – Fumigation, sterilization of biological products </li></ul>
  16. 16. CHEMICAL AGENTS <ul><li>Surface active agents –Reduces surface tension– - anionic, cationic*, nonionic, amphoteric. Detergents, and emulsifiers. Cetavlon, cetrimide </li></ul><ul><li>Metallic salts – Salts of Ag, Cu, Hg. Mercuric Chloride, mercurochrome, thiomersal, phcnyl mercuric nitrate, AgNO3, CuSO4. </li></ul>
  17. 17. REMEMBER! <ul><li>During sterilization, only a fraction of microorganisms die in a given time interval </li></ul><ul><li>Cleaning is the first and imp step in chemical disinfection </li></ul><ul><li>For washing, use running water not > 60 degrees C (to prevent protein coagulation) </li></ul><ul><li>Total surface contact is essential </li></ul><ul><li>Recommended strengths should be adhered to </li></ul><ul><li>Chemicals can get contaminated by incorrect use </li></ul><ul><li>Time-temperature relationship </li></ul><ul><li>Some organisms are very resistant to chemical agents – Pseudomonas Aeruginosa </li></ul><ul><li>Incineration is the safest method of sterilizing and disposing infected dressings </li></ul>