1 / 27

Sterilization & Disinfection Physical Agents

Sterilization & Disinfection Physical Agents. Hugh B. Fackrell PhysSter.ppt. Sterilization & Disinfection. Definitions Bacterial Cell Death Physical methods Heat Radiation Filtration. Definitions. Sterilization Complete Destruction of ALL microbes Disinfection

copet
Download Presentation

Sterilization & Disinfection Physical Agents

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sterilization & DisinfectionPhysical Agents Hugh B. Fackrell PhysSter.ppt

  2. Sterilization & Disinfection • Definitions • Bacterial Cell Death • Physical methods • Heat • Radiation • Filtration

  3. Definitions • Sterilization • Complete Destruction of ALL microbes • Disinfection • Killing of pathogens on inanimate objects • physical or chemical • Antiseptic • A chemical agent for disinfection of living tissue • External skin, mouth vagina

  4. Definitions • Bacteriocide • kill microbes • also germicide, fungicide, virucide • Bacteriostatic • Prevents or stops microbial growth • also fungistatic, virustatic • Aseptic(Asepsis) • Prevent contamination of person or object by microbes

  5. Definitions • Sanitize • Removal of pathogens from inanimate objects • Mechanical or chemical cleaning • need not sterilize of disinfect • Contamination • Presence of living microbes on object

  6. Definitions • Infection • Presence of living multiplying microbes in host tissues • often pathogenic

  7. Survivors (log) 1 log decrease = 90% kill 5 1 log Death rate (D) varies with bacteriocide 4 3 2 D 1 Time(min) to kill 90% 0 Time (min) Bacterial Cell Death

  8. Physical Methods • Heat • Radiation • Filtration

  9. Heat Sterilization • Factors • length of exposure • temperature • “Moist Heat” • “Dry Heat” Method of choice

  10. “Moist” heat • Effective quickly against most pathogens • low thermal death point • 60-70% in 10 min • Pasteurization 60-70 oC Sanitizes • Hot water 60-100 oC Disinfects • Steam 15 psi 121oC Sterilizes Endospores resist boiling for hours!!

  11. Heat: Mechanism of Action • Inactivation of enzymes • Structural changes • coagulation of proteins • Oxidation • membrane disruption

  12. Pasteurization • Liquids • Minimal heat • 145 oF (62.9 oC) - 30 min • 162 oF (71.6 oC) - 15-30 sec • Flavour of drink preserved • Kills non spore forming pathogens • TB. Brucella, Salmonella, Streptococcus • Kills spoilage bacteria • Lactobacillus, Streptococcus

  13. “Flash” Pasteurization • 72 oC - 15 sec • 88 oC - 1 sec • 90 oC 0.5 sec • 96 oC 0.05 sec Raw milk Heating coil Cooling coil

  14. Boiling Water • 100 oC (212 oF) 10- 30 min • Disinfectant • spores & some viruses are resistant • Safe for clean instruments that DO NOT penetrate the tissue • Soiled items -add detergent

  15. Steam Under Pressure • Autoclave • 15 psi 121 oC 250 oF • Time 15 min - dependent on volume • Steam displaces air & penetrates • Packing of autoclave critical! • Airlocks in packing • reduce effective temp & pressure

  16. Dry Heat • Longer & hotter • Oxidation • Carbonization • cotton plugs

  17. Types of Dry Heat • Oven • 160-165 oC 2 hours • 170-175oC 1 hr • Glass, oils, waxes, glycerin • Incineration • destruction of pathological material • Flaming • used as aseptic techniques • scissors, scalpels, loops, needles

  18. Radiation Sterilization • Ionizing Radiation • Ultraviolet Radiation * Point mutations involve changes in only one or a few nucleotides

  19. Ionizing Radiation Increased energy Radiant Energy spectrum UV light

  20. Sterilization by Ionizing Radiation • Gamma Rays • Food • Plastics • Electron Beams • pharmaceuticals Human Hazard!

  21. Ionizing Radiation • Creates free radicals • Causes breaks in two DNA strands • Results in deletions • Results in translocations

  22. Free radicals can breaks both phosphodiester bonds of a DNA helix Free Radicals • High Energy Radiation • energy absorbed by atoms • energy added to electrons • electrons ejected from atoms • leaves ionized atoms & unpaired electrons

  23. Sterilization by Ultraviolet light • Circulating air • Surfaces • benchtops • Small samples of liquid Surfaces only poor penetration Photoreactivation white light reverses effect of ultraviolet

  24. Ultraviolet Radiation • Pyrimidine dimers • errors during repair • Peroxides, Free radicals • See ionizing radiation • Direct molecular damage • intense exposure

  25. TT GTA GTC CATAACAG TT A GT GTC CATAACAG TT A G GT GTC CATAACAG GTA T GTC CATAACAG GTA TTGTC CATAACAG Repair of thymine dimer

  26. Filtration Sterilization • HEPA filters • High Efficiency Particulate Air filter • Remove airborne microbes • Filters particles >0.3 mm • Operating rooms • “Clean rooms” instrument assembly • Burn patients • Immunocompromized

  27. Filter sterilization • Membrane filters • cellulose nitrate or synthetic polymers • Pore size • bacteria 0.22mm 0.45 mm • viruses 0.01 mm • Sterilize heat or energy sensitive materials • bacterial media • drug solutions

More Related