Key concepts:
    1.  Sterilization
    2.  Disinfection
    3.  Parameters which affect sterilization or disinfection success
    4.  Methods for sterilization and disinfection
 
I.  Approaches to control
    A.  Sterilization
    B.  Disinfection
        1.  Disinfectant, antiseptic, decontamination, sanitation
    C.  Germicide
    D.  Bacteriostatic

II.  Principles involved in killing microorganisms
    A.  Only a fraction of microorganisms die during a given time interval during sterilization.
        1.  Fraction is constant.
        2.  Death curve is logarithmic.
    B.  Factors influencing the effectiveness of antimicrobial treatments:
        1.  Time of exposure
        2.  The number of microbes
        3.  Environmental influences
        4.  Microbial characteristics

III.  Actions of Microbial Control Agents
    A.  Alteration of membrane permeability
    B.  Damage to proteins and  nucleic acids

IV.  Physical Methods of Control
    A.  Dry heat - slow, high temperature required.
        1.  160-170 degrees C for 2-3 hours in dry oven.
        2.  Used for glassware, non-food objects

    B.  Boiling - drinking water, primarily.
        1.  100 degrees C for 10 minutes
        2.  Effective against vegetative cells and viruses, not endospores.

    C.  Autoclaves - moist heat
        1.  Water and steam produced at temperatures greater than 100 degrees C
        2.  Autoclave - modern pressure cooker
        3.  Usual conditions - 15 psi, 121 degrees C, 15 mintues - kill every possible life form, including endospores.

    D.  Pasteurization - controlled heating at temperatures below boiling
        1.  Effective against pathogenic vegetative cells, not endospores.
        2.  HTST, LTLT, UHT methods

   E.  Filtration
        1.  Used for fluids that are heat-sensitive
        2.  Microscopic sieves which hold back microbes while allowing fluid to pass through.
        3.  Problems with filters.

    F.  Low Temperatures

    G.  Dessication

    H.  Osmotic Pressure

  I.  Radiation
    A.  ionizing radiation - gamma rays, X-rays etc.
        1.  produce hyperreactive ions which destroy biological macromolecules
        2.  not sterilant
        3.  Used to disinfect plastics etc
        4.  Alternative to ethylene oxide gas
    B.  Nonionizing - UV light   (200-310 nm)
        1.  absorbed by DNA and induces damage leading to cell death
        2.  actively growing cells killed most effectively; endospores are most resistant.

V.  Chemicals involved in sterilization, disinfection and preservation
    A.  Alcohols
        1.  Ethyl and Isopropyl alcohols
        2.  Disinfectants
        3.  Act by coagulating proteins in cells.

    B.  Halogens - chlorine and iodine
        1.  Act by oxidizing proteins and other important biological macromolecules.
        2.  Chlorine - mostly used for drinking water and swimming pools.
            a.  0.5 ppm in drinking water
            b.  skin and mucous membrane irritant
        3.  Iodine - enhanced activity by dissolving in alcohol (tincture of iodine)
            a.  not reliable for killing endospores
        4.  Disinfectants

    C.  Aldehydes
        1.  Act by coagulating proteins.
        2.  Formaldehyde
            a.  8% in water is an effective disinfectant killing most microorganisms including endospores and viruses,
                    but more dilute solutions do not kill endospores and viruses.
            b.  irritating vapors and suspected carcinogen
        3.  Replaced by glutaraldehyde
            a.  an effective sterilization agent when used in high concentration and for 10-12 hour-long treatments.
        4.  Disinfectants

    D.  Phenolics
        1.  5-10% solutions are active against most vegetative cells, including M. tuberculosis.
        2.  Destroy cell membrane.
        3.  5% effective against viruses
        4.  Cheap, broad spectrum and easily incorporated into soaps and detergents.
        5.  Used to decontaminate hospital operating rooms.
        6.  Derivatives: hexachlorophene and chlorhexidine.

    E.  Quaternary Ammonium Compounds (Quats)
        1.  Destroy cell membranes
        2.  surface-active agents
        3.  Used to disinfect (sanitize) clean inanimate objects
        4.  Used as a preservative in non-food substances.

    F. Metal compounds - mercury and silver
        1.  Mercury compounds not used any more due to weak antimicrobial properties.
        2.  1% silver nitrate solutions
        3.  Silver sulfadiazine is used to treat burn victims.

    G.  Ethylene oxide gas
        1.  The only chemical that is a reliable sterilization agent.
        2.  Penetrates many fabrics and objects
        3.  Used to sterilize medical devices, plastics, rubber objects and other heat-sensitive materials.
        4.  Requires a special chamber, explosive.

    H. Chemical Preservatives - prevent or retard spoilage
        1.  Phenolics and Quats

    I. Antibiotics - none of these are antibiotics; we will learn more about Antibiotics in Chapter 20.

   J.  Important factors in proer use of a germicidal agent: dilution, temperature, time of treatment, cleanliness of object,
            free of organic matter, number of microorganisms present, growth phase of microorganisms.