Control Microbe Growth

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Control Microbe Growth
2015-03-15 23:36:17

Control Microbe Growth
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  1. Microbial Growth Control is Needed in
    •Daily life


    •Microbiology laboratories

    •Food production industry

    •Other industries
  2. Sterilization
    Removal or destruction of all forms of microbial life
  3. Disinfection
    Control directed at destroying harmful microorganisms. Destruction of vegetative pathogens on inert surface
  4. Antisepsis
    Destruction of vegetative pathogens on living tissue
  5. Asepsis
    Object or area is free of pathogens
  6. Degerming
    Mechanical removal of most of the microbes in a limited area
  7. Sanitization
    any cleansing technique that mechanically removes microbes
  8. Bacteriostasis
    inhibition of growth and multiplication of bacteria
  9. Biocide/Germicide
    kills microorganisms with exception of endospores
  10. Selection of an Antimicrobial Procedure
    •Type of microbe – ‘tough bugs’

    •Number of microbes present

    • •Environmental conditions
    • –Organic material present?
    • –Temp & pH (warm disinfectant vs
    • cold?)

    •Potential risk of infection
  11. Relative susceptibilities of microbes to antimicrobial agents
    Most resistant: Prions, endospores, mycobacteria

    Most susceptible: Enveloped viruses, G+ bacteria, non-enveloped viruses
  12. Virus structure: Naked
    Without a lipid envelope

    •Protein capsid
  13. Virus structure: Enveloped
    With a lipid envelope covering the outside of the virus

    •Phospholipid envelope
  14. Microbial control
    Moist heat: lower temperatures and shorter exposure time; coagulation and denaturation of proteins



    •Commercial canning

  15. Boiling Water
    • •Boiling at 100oC for 30 minutes to destroy
    • non-spore-forming pathogens

  16. Pasteurization
    • •Pasteurization – heat is applied to kill potential
    • agents of infection and spoilage without destroying the food flavor or value
  17. Dry Heat
    • •Dry heat: uses higher temperature than
    • moist heat

    •Hot oven (hot-air sterilization)

    •Direct flaming
  18. Filtration of liquids
    •Filter size excludes microbes (≤0.22 mm)

    •Used for heat-sensitive liquids

    –Ex. Antibiotics, vitamins, amino-acids
  19. Filtration of Air
    • •HEPA filters: high-efficiency particulate
    • air filters (0.3 mm)

    •Infection-control rooms or laboratories
  20. Ionizing radiation
    Gamma rays

    •Produces reactive molecules that damage DNA

    •Hydroxyl radicals, superoxide

    •Used for sterilization of plastic disposables, Petri dishes

    •Used in food preservation
  21. Non-ionizing radiation
    UV light

    • •Little penetrating power -  must be directly
    • exposed

    •Damages DNA

    •“Germicidal lamps”
  22. Organic Acids
    • controls fungi, and some bacterial growth
    • in foods & cosmetics
  23. sodium benzoate
    •found naturally in cranberries, prunes, apples, cinnamon, cloves

    Benzoic acid - naturally occurring compound; totally safe and has no adverse health implications

    Benzene - known carcinogen