1. Microbiology: Principles and Explorations Sixth Edition Chapter 12: Sterilization and Disinfection Copyright © 2005 by John Wiley & Sons, Inc. Jacquelyn G. Black

2. Principles of Sterilization and Disinfection Disinfectant: Typically chemical agents that are applied to inanimate objects Antiseptics: Typically chemical agents that are applied to living tissues Table 12.1

3. Sterilization: The killing or removal of all living cells, viable spores, viruses in a material or on an object Sterility: there are no living organisms in or on an object Disinfection: The reduction of the number of pathogenic microorganisms to the point that they pose no danger of disease

4. Disinfectant and Antiseptic Response of Staphylococcus aureus

5. Disinfectant and Antiseptic Response of Escherichia coli

6. Denaturing Proteins

7. Action of a Surfactant

8. Structural Formulas of Common Disinfectants

9. Heavy Metal Effect on Bacterial Growth

10. Biodecontamination Unit—Hydrogen Peroxide

11. Biodecontamination Unit—Ethylene Oxide

12. Sterilization—Hot Air Oven

13. Small Countertop Autoclave

14. Model Autoclave

15. X rays and gamma rays are forms of ionizing radiation So named because it can dislodge electrons from atoms creating ions Damages DNA and produces peroxides (powerful oxidizing agents in cells) Deinococcus radiodurans: Able to survive 1000X the amount of radiation that would kill a human (bioremediation of radioactive contaminated sites) Ionizing Radiation

16. If water is heated under pressure, its boiling point is elevated, so temperatures above 100 o C can be reached Pressure: 15 lbs per square inch (psi) 15 – 20 minutes at 121 o C Prions are highly resistant and must be sterilized longer and at higher temperature (134 o C for 18 min) Autoclaving

17. Checking for Sterility

18. Pasteurization A process invented by Pasteur to destroy microbes that caused wine to sour, does not achieve sterility Kills pathogens: Salmonella and Mycobacterium Milk is pasteurized by heating it to 71.6 o C for at least 15 seconds (flash method) Milk is pasteurized by heating it to 62.9 o C for 30 minutes (holding method)

19. Large Automatic Hospital Autoclave

20. Preservation by Drying

21. Lyophilization—Stoppering Tray Dryer

22. Lyophilization— Manifold Dryer

23. A definite proportion of the organisms die in a given time interval The fewer organisms present, the shorter the time needed to achieve sterility Microorganisms differ in their susceptibility to antimicrobial agents The most susceptible phase for most organisms is the logarithmic growth phase The Control of Microbial Growth

24. Germicide: An agent capable of killing pathogens and nonpathogens but not necessarily endospores Bacteriostatic agent: An agent that inhibits the growth of bacteria 1.Bactericide 2.Bacteriostatic

25. The Use of Physical Methods in Control of Microbial Growth Heat and other physical agents are normally used to control microbial growth and sterilize objects: 1.Heat 2.Low Temperatures 3.Filtration 4.Radiation

26. Heat One of the most popular ways to destroy microbes (flame or boiling) Moist or Dry heat may be used Exposure to boiling water for 10 minutes is sufficient to destroy vegetative cells and eukaryotic spores Steam sterilization (autoclaving) is necessary to destroy the bacterial endospore

27. Radiation Ultraviolet radiation (260nm): is quite lethal in destroying microbes but it does not penetrate glass, dirt films, or water Ionizing radiation (IR): An excellent sterilizing agent because of its ability to penetrate deep into objects IR will destroy bacterial endospores and both prokaryotic and eukaryotic vegetative cells

28. UV Radiation—Serratia marcescens

29. Microwave Sterilization

30. Filtration Sterilization

31. Filtration Can be used to sterilize substances that are destroyed by heat (drugs, serum, vitamins, sucrose) To separate viruses from bacteria (manufacture of vaccines) To collect microorganisms from air and water samples (water quality testing)

32. Staphylococcus epidermidis on surface of 0.22  m Millipore Membrane Filter