Micro Chap 7/Exam 2

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Micro Chap 7/Exam 2
2013-04-02 16:05:09
LCCC Microbiology Microbacterial Growth

For DeAngelo's Exam 2
Show Answers:

  1. Define Sterilization
    • Destruction or removal of all forms of microbial life, including endospores but with the possible exception of prions
    • -usually done by steam under pressure or a sterilizing gas, such as ethylene oxide
  2. Define Commercial Sterilization
    • sufficient heat treatment to kill endospores of Clostridium botulinum in canned food
    • -more-resistant endospores of thermophilic bacteria may survive  but they will not germinate and grow under normal storage conditions
  3. Define Disinfection
    • Destruction of vegetative (growing) pathogens
    • -may make use of physical or chemical methods
  4. Define Antisepsis
    • Destruction of vegetative pathogens on living tissue
    • -treatment is almost always by chemical antimicrobials
  5. Define Degerming
    • removal of microbes from a limited area, such as the skin around an injection site
    • -mostly a mechanical removal by an alcohol-soaked swab
  6. Define Santization
    • treatment is intended to lower microbial counts on eating and drinking utensils to safe public health levels
    • -may be done with high-temperatue washing or by dipping into a chemical disinfectant
  7. What does it mean when something is "cidal" or "static"?
    cidal- kills whatever it is made for ex. mesocidal

    static-halts growth (like a fridge is microbial static for mesophiles)
  8. What is DRT? What are the two factors that can affect DRT?
    • DRT is the time it takes to kill 90% of the microbial population
    • -varies between MOs

    • *the Harsher the procedure, the shorter the DRT
    • *the easier the MO to kill, the shorter the DRT
    • *does not vary under a defined set of conditions (constantly killing 90%)
  9. How can the number of microbes and degree of microbial resistance influence the effectiveness of microbial treatments?
    More microbes= more time to kill them all

    The easier they are to kill, the less time it takes to kill them
  10. How can environmental influences and exposure time influence the effectiveness of microbial treatments?
    Cold, dirty objects are harder to treat-disinfection is a chemical process, which occurs faster at warmer temperatures-dirt:organic matter; can absorb disinfectant and prevent the killing of MO*the longer you kill, the more you kill
  11. What are the three factors of cell anatomy that are important in how microbial control agents effect the cells?
    • These 3 are targets for killing
    • membrane-regulates what enters the cell.  If damaged, cell with lyse

    proteins-do certain jobs that keep the cell alive. If damaged, cell will die

    nucleic acids-controls the synthesis of proteins. If damaged cell will die
  12. What is the purpose of boiling? What are it's uses and limitations?
    Common uses: for cleaning drinking water, boil for 2 minutes

    *boiling is 100C

    how? It denatures the proteins of the MO (like a hardboiled egg)

    • Limitations: some spores survive boiling
    • *form of disinfecting or sanitization
  13. What is the purpose of an autoclave? How does it work? What are it's uses and limitations?
    • Works like a pressure cooker
    • -the steam is much hotter than boiling
    • -121C for 15 minutes

    • Microbes cannot survive
    • -reliable sterilization

    limitation: only for objects that can get hot and wet
  14. What is the purpose of pasteurization? How does it work? What are it's uses and limitations?
    Pasteur's Idea-goal is to kill pathogens and lower total MO count without significantly altering taste or nutrient content

    uses: milk, beer, fruit juice, canned crab meat, marschino cherries

    • timing: 63C/30min;72C/15sec;
    • UHT 74C-->140C-->70C in 5 seconds

    UHT: ultra high temperature

    -it extends the products shelf life and makes the product safe to consume
  15. What is the purpose of oven sterilization? How does it work? What are it's uses and limitations?
    • Uses Dry Heat
    • -170C for 2 hrs

    Organic Molecules + Heat--> CO2 + H2O

    Air conducts heat much more porrly than water, that's why it takes longer than autoclaving

    limitations: use for objects that can get hot but not wet (like glassware)

    related methods: flaming loops, incineration of infectious waste
  16. What is the purpose of filtration? How does it work? What are it's uses and limitations?
    This is used for fluids that are heat-liable, or damaged by heat such as culture media enzymes, vaccines, and antibiotic solutions

    • Uses: can be used for water at (.2μm)
    • HEPA filters (.3μm) for burn wards, clean rooms, operating filters
  17. What is the purpose of refrigeration?  How does it work? What are it's uses and limitations?
    normally set at 4C, it is microbiostatic for mesophles

    permits slow growth of psychrotrophs (usually non pathogens except for Lysteria)
  18. What is the purpose of high osmotic pressure? How does it work? What are it's uses and limitations?
    The more hypertonic the solution is, the higher the osmostic pressure is


    examples: salting, sugaring, drying of foods

    many molds are osmotolerant, explaining mold growth on bread, etc
  19. What is the purpose of Ionization radiation? How does it work? What are it's uses and limitations?
    A Sterilization process

    examples: gamma rays, X-rays, electron beams (all are highly penetrating)

    • mechanism: production of hydroxyl radicals in water and direct damage to DNA
    • H2O + IR --> OH-
    • * these hydroxyl radicals are potent oxidizers of DNA and proteins

    Applications: food, (sterilizer of pasteurizer  depending on intensity and exposure time), mail, prepackaged disposable medical/dental/laboratory tools

    *sometimes referred to as "cold pasteurization" or "electronic pasteurization"
  20. What is the purpose of Non-ionizing Radiation? How does it work? What are it's uses and limitations?
    • UV radiation, provided by UV (germicidal) lamps
    • -like Tru-D in hospitals to kill c. diff

    mechanism: DNA strongly absorbs UV radiation and is often damaged in doing so

    Limitations: UV rays are poorly penetrating  so use is limited mostly to disinfection of surfaces or air

    Applications: disinfection of well water, operating thearres, barber shops, nail salons
  21. What are the factors related to the effective disinfection?

    • -type of organism the disinfectant is effective against
    • -concentration of the disinfectant
    • -whether the disinfectant can contact the microbes (non porous surfaces)
    • -contact time
  22. Triclosan
    common in household antibacterial soaps; inhibits fatty acids (and thus membrane) synthesis
  23. Iodine
    very effective; binds to and inactivates many microbial proteins; used as a skin antiseptic (e.g. betadine) and to disinfect drinking water (hikers use tablets)
  24. Chlorine
    strong oxidizing agent; active ingredient in bleach; used to disinfect drinking water, swimming pools; 10% sol'n can be used in sharps containers or to disinfect surfaces
  25. Alcohols
    denatures proteins and dissolves lipid membranes; used as a degermer (injections, hand gel-sanitizers)
  26. Soaps
    just a degermer (provided no anti-bacterial agents have been added to it); but don't underestimate the effectiveness of correct hand washing procedures with soap and hot water
  27. Quaternary Ammonium Compounds
    lots of different specific types (e.g. alkyl dimethyl benzyl ammonium chloride, benzalkonium chloride, etc.)  Probably disrupts membrane; soapy, very common in household disinfectant products (kitchen and bathroom cleaners, disinfectant wipes, contact lens cleaners, etc)

    Pseudomonas can use this as a nutrient!!
  28. Potassium Sorbate
    A mold inhibitor, often found in soft drinks, cheeses and baked goods (like snack cakes)
  29. Sodium Benzoate
    same as potassium sorbate
  30. Glutaraldehyde
    highly effective; one of the few chemicals considered to be a sterilent (when properly used); bind to and denature cell proteins; the active agent in our laboratory bench top cleaning solutions (wavicide)
  31. Ethylene Oxide
    an explosive and possibly carcinogenic gas-but highly penetrating and effective. denatures proteins; used in autoclave-like devices (gas sterilizers  to sterilize hospital equipment (e.g. bronchoscopes) and sealed, disposable materials (swabs, bandages, etc.)
  32. Hydrogen Peroxide
    Oxidizing Agent; not very effective on wounds due to catalase in human tissue; but works very well on inanimate surfaces; used to disinfect contact lenses and sterilize food packages like juice boxes
  33. Benzoyl Peroxide
    an oxidizing agent found in over-the-counter acne medications-effective against the anaerobic bacteria that dwell deep in the hair follicle
  34. What is the deceasing order or microbial resistance to chemicals?