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MICROBIAL CONTROL - PowerPoint PPT Presentation

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MICROBIAL CONTROL. MICROBIAL CONTROL METHODS. Physical Control Heat Cold/ Dessication Radiation Autoclave Chemical Agents Categories of chemicals Household products (listed next page). HOUSEHOLD PRODUCTS. CONTROLLING MICROORGANISMS.

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  • Physical Control

    • Heat

    • Cold/Dessication

    • Radiation

    • Autoclave

  • Chemical Agents

    • Categories of chemicals

    • Household products (listed next page)



  • Decontamination- the destruction, removal or reduction in number of undesirable microbes

  • 4 methods of decontamination

    • Sterilization

    • Disinfection

    • Sanitization

    • Degermation

  • STERILIZATION- Removal or destruction of all viable microbes

    • Autoclaving, ionizing radiation

  • DISINFECTION- Destruction of vegetative pathogens on an inanimate object

    • 5% bleach, boiling water

  • Disinfection does not usually kill bacterial spores whereas sterilization destroys all organisms.

  • Difference between disinfection and sterilization?

  • Disinfection is only a reduction of microbial load on an object. An object that has been disinfected is less likely to transmit infection than one that hasn't but because there is only a reduction in the number of microorganisms, there is no guarantee.

  • Sterilization is absolute. It means that ALL of the microorganisms have either been removed or killed. A sterile object has NO viable microbial cells present.

  • SANITIZATION is a cleansing technique that removes microorganisms and debris from inanimate objects

    • Dishwashing, laundering clothes

    • Sanitizing your toothbrush is important because bacteria can build up from daily use.

  • DEGERMATION cleansing technique that removes microorganisms and debris from living tissue

    • Alcohol wipes, surgical handscrub

Here is a review of key concepts of hand hygiene….

  • Health care-associated infections affect hundreds of millions of patients worldwide every year. Infections lead to more serious illness, prolong hospital stays, induce long-term disabilities, add high costs to patients and their families, contribute to a massive, additional financial burden on the health-care system and, critically, often result in tragic loss of life. (WHO, 2009)


Some things to consider if using HEAT……

  • Can use moist heat or dry heat

  • Practical Concerns in the Use of Heat: Thermal Death Measurements

    • Thermal death time (TDT): the shortest length of time required to kill all test microbes at a specified temperature

    • Thermal death point (TDP): the lowest temperature required to kill all microbes in a sample in 10 minutes

  • Temperature and length of exposure must be considered

  • Higher temperatures generally allow shorter exposure times; lower temperatures generally require longer exposure times



    • The main benefit of cold treatment is the slow growth of cultures and microbes in food during processing and storage.

    • Cold does not kill most microbes; freezing can actually preserve cultures

    • Desiccation: dehydration of vegetative cells when directly exposed to normal room air

    • Lyophilization: a combination of freezing and drying; used to preserve microorganisms and other cells in a viable state for many years


    Radiationis energy emitted from atomic activities and dispersed at high velocity through matter or space

    • Ionizing radiation (X rays, gamma rays, electron beams)

      • Ionizes water to release hydroxide

      • Damages DNA

    • Non-ionizing radiation (UV, 260 nm)

      • Damages DNA

    • Microwaves kill by heat; not especially antimicrobial

    Many foods can be effectively sterilized by utilizing the penetrating power of ionizing radiation.


    • Here is an example of how to clean a tattoo machine with an autoclave

    • http://www.youtube.com/watch?v=huStW067-jI&feature=related


    Chemicals are divided based on their level of effectiveness and the surfaces to which they are applied.

    • Antiseptics: microbicidal agents harmless enough to be applied to the skin and mucous membrane; should not be taken internally.

      • Alcohols, mercurials, silver nitrate, iodine solution, detergents.

    • Disinfectants: agents that kill microorganisms, but not necessarily their spores, but are not safe for application to living tissues; they are used on inanimate objects such as tables, floors, utensils, etc.

      • Hypochlorites, chlorine compounds, lye, copper sulfate, quaternary ammonium compounds, formaldehyde and phenolic compounds.


    • Chemotherapeutic agents (synthetic antibiotics): antimicrobial agents of synthetic origin useful in the treatment of microbial or viral disease. These are examples:

      • sulfonilamides, isoniazid, ethambutol, AZT, nalidixic acid and chloramphenicol.

    • Antibiotics: antimicrobial agents produced by microorganisms that kill or inhibit other microorganisms

    These chemicals approach the ideal by having many of the following characteristics: broad spectrum, low toxicity, fact action, penetrating abilities, residual effects, stability, potency in organic matter and solubility.

    Works Cited

    • Lowry, Doc. "Tattoo Machines & Guns : How to Clean a Tattoo Machine." YouTube Broadcast Yourself. 15 Nov. 2008. Expert Village. 1 Apr. 2011 <http://www.youtube.com/watch?v=huStW067-jI>.

    • "Microbiology in the news." American Society for Microbiology. 30 Mar. 2011. 20 Apr. 2011 <http://www.asm.org/>.

    • Talaro, Kathleen P., Marjorie Kelly. Cowan, and Barry Chess. Foundations in microbiology. Boston: McGraw-Hill, 2009.

    • Todar, Kenneth. "Control of Microbial Growth." Online Textbook of Bacteriology. 24 Apr. 2011 <http://www.textbookofbacteriology.net/control.html>.

    • United Kingdom. World Nuclear Association. London SW1Y 4JH. World Nuclear Association | Nuclear Power - a Sustainable Energy Resource. 1 Apr. 2011. 2 Apr. 2011 <http://www.world-nuclear.org/info/inf05.html>.

    • "WHO | World Health Statistics 2009." World Health Statistics 2009. 2009. World Health Organization. 24 Mar. 2011 <http://www.who.int/whosis/whostat/2009/en/index.html>.

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