Lab 11 study guide

  1. define antiseptic
    chemicals that may be applied safely to skin or other biological tissues
  2. define disinfectant
    • chemicals that kill or inhibit the growth of vegetative cells on the surfaces of nonliving materials
    • more toxic than antiseptics
  3. zone-of-inhibition method
    • apply the chemical to a freshly inoculated plate
    • incubate the culture
    • look for the zone of inhibition (area of no growth)
    • zone only shows if bacteria has been killed or slowed growth--can't tell which
  4. define bacteriostatic
    slows growth of bacteria
  5. define bactericidal
    actually kills bacteria
  6. difference between antiseptic and disinfectant
    • antiseptics used on skin
    • disinfectants used to kill bacteria on hard nonliving surfaces
  7. antiseptic that denatures proteins, dissolves lipids and dehydrates cells
  8. antiseptic that is a strong oxidizing agent
  9. antiseptic that is used in the eyes of newborns to prevent transmission of gonococci
    heavy metals
  10. antiseptic that denatures enzymes and destroys membranes
  11. antiseptic that is used in mouthwashes and gargle solutions
    phenols (thymol)
  12. Many household disinfectants are strong ________ agents.
  13. Explain why it is important to use a combination of agents or to frequently change agents when using antiseptics or disinfectants
    The continued application of a single agent will select for microbial mutants that are resistant to that agent. That risk is minimized when you use higher concentrations and is almost eliminated when ytou use a combination of effective agents.
  14. What is difference between bacteriostatic and bactericidal?
    Can zone of inhibition discriminate between the two?
    • bacteriostatic only slows the growth of organisms
    • bactericidal kills organisms
    • zone of inhibition does not discriminate between the two. don't know if the organism was killed or slowed.
  15. Why shouldn't zone size alone be used to determine the effectiveness of an antiseptic or disinfectant?
    The size of the zone depends not only on the effectiveness of the antiseptic or disinfectant but also on its ability to diffuse into the medium. Even a very effective chemical that does not readily diffuse out from its source will not produce a very large zone of inhibition.
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Lab 11 study guide
lab 11 study guide