1. Control of Microbial Growth (Sterilization and Disinfection)

2. Control of Microbial Growth
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3. Microbial Control
Can inhibit growth of many microorganisms by washing and scrubbing with soaps and detergents.

4. Sterilization
Process of removing or killing all microorganisms and viruses on or in a product.
Ensures complete destruction of all microorganisms, including cells, spores, and viruses.

5. Examples of Sterilization
Dry heat
Autoclaving
Gas
Various chemicals
Certain types of radiation
Autoclave.
Dry Heat Sterilization.

6. Disinfection
Process that reduces # of potential disease-causing bacteria and viruses on a material until they no longer present a hazard.
Terms decontamination and sanitation mean the same thing generally.
Disinfectant
A chemical used to disinfect inanimate objects.

7. Example of Disinfection - Pasteurization
Method of disinfecting liquids.
Heat liquids to a certain temperature.
Does not totally destroy pathogens.
Pasteurization Equipment.

8. Decontamination
Inactivation or removal of both microbial toxins and the living microbial pathogens.

9. Antiseptic Solutions used to disinfect skin and other living tissues.

10. Sanitation
Reduction of microbial populations to levels considered safe by public health standards.

11. Microbicidal Agents The suffix –cide or –cidal refers to “killing.”
Ex. Microbicidal agents (microbicides)
Ex. Bactericidal agents
Ex. Sporicidal agents
Ex. Viricidal agents

12. Microbistatic Agents Microbistatic Agent Bacteriostatic Agent
Drug or chemical that inhibits the growth and reproduction of microorganisms.
Bacteriostatic Agent
One that specifically inhibits the metabolism and reproduction of bacteria.
Microbistatic technique examples
Ex. Lyophilization (freeze-drying)
Ex. Rapid freezing (using liquid nitrogen)

13. Some Useful Terms Sepsis Asepsis Antisepsis Antiseptic technique
Presence of pathogens in blood or tissues.
Asepsis
Absence of pathogens.
Ex. Hand washing; use of sterile gloves, masks, gowns; sterilization of surgical equipment; use of disinfectants.
Antisepsis
Prevention of infection.
Antiseptic technique
Developed by Joseph Lister (1867).
Use of antiseptics.
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14. Sterile Technique
Practice of excluding all microorganisms from a particular area, so that the area will be sterile.
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15. Controlling Microbial Growth Using Physical Methods
Methods used to destroy or inhibit microbial growth may be physical or chemical.
Examples:
Heat
Combination of heat and pressure
Desiccation
Radiation
Sonic disruption
Filtration

16. Heat Practical, efficient, and inexpensive method of sterilization.
2 factors that influence effectiveness of heat for sterilization: temperature and time
Thermal Death Point (TDP)
Lowest temperature that will kill all organisms in a standardized pure culture within a specified period.
Thermal Death Time (TDT)
Length of time necessary to sterilize a pure culture at a specified temperature.

17. Dry Heat Heating materials in absence of moisture.
Must be baked at 160º to 165ºC for 2 hours or at 170º to 180ºC for 1 hour.
Other methods include incineration and flaming surface of metal materials like forceps and loops.
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18. Moist Heat Boiling or steaming.
Most pathogens destroyed after 30 minutes of boiling.
Boiling not always effective against some endospores and viruses.
Boiling not an option for thermophiles.
Boiling. ttt.astro.su.se
Steamer.

19. Autoclaving
Large metal pressure cooker that uses steam under pressure to completely destroy all microorganisms.
Increased pressure raises the temperature of boiling water (i.e. above 100ºC) producing steam.

20. Home Canning Use of a pressure cooker.
If foods canned without pressure some bacterial endospores may survive.
i.e. Clostridium botulinum
Bulging lid – botulism. calorielab.com

21. Disinfecting Techniques
For clothing, bedding, and dishes
Use hot water with soap or detergent
Agitate solution around items
Combination of heat, mechanical action, and chemical inhibition kills most microbes.
Washing Machine.

22. Cold Metabolic activities slowed.
Most microbes not killed, but growth inhibited.
Slow freezing not a good way to preserve bacteriological or biologic specimen.
Rapid freezing (liquid nitrogen) good for this.
Why should you not refreeze foods?
Slow Freezing.
Rapid Freezing – liquid nitrogen. encarta.msn.com

23. Desiccation Process of drying materials.
Many microbes can remain viable despite absence of nutrients and moisture.
Ex. Lyophilization (freeze-drying)
Dried blood, fecal material, and dust may still contain viable microbes.

24. Radiation
Ultraviolet (UV) light sometimes used to prevent or decrease microbial growth.
X-rays and gamma and beta rays may be used to destroy or prevent microbial growth.

25. Ultrasonic Waves Often used to sterilize and clean delicate equipment.
Consists of tanks filled with liquid solvent (usually water).
Short sound waves are passed through liquid.
Sound waves dislodge organic debris.
Materials must then be washed and sterilized by another method.

26. Filtration
Filters of various pore sizes are used to filter or separate larger cells, larger viruses, bacteria, and other microbes from gases or liquids in which they are suspended.
Paper masks used to prevent the outward and inward movement of microbes.
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27. Gaseous Atmosphere Altering atmosphere of microbes to inhibit growth.
Gas gangrene – caused by Clostridium spp.
Hyperbaric Chamber.

28. Chemical Agents Used to Inhibit Microbial Growth
Temporarily or permanently.
Different disinfectants have different properties.
Disinfectants should be chosen based on their efficiency and effectiveness for a particular situation.

29. What Are Some Things to Consider When Choosing a Chemical Disinfectant?

30. What makes an Ideal Chemical Antimicrobial Agent?

31. How Do Disinfectants Kill Microorganisms?
Some target and destroy cell membranes.
Ex. Surface-active soaps and detergents; alcohols
Some destroy enzymes and structural proteins.
Ex. Formaldehyde and ethylene oxide
Some attack cell walls or nucleic acids.

32. Antiseptics Can be used safely on human skin.
Reduces # of organisms on the surface.
Does not penetrate pores or hair follicles.

33. Preventing Growth of Pathogens in Our Kitchens

34. The Antibiotic Controversy

35. The End