Micro Test 2

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Micro Test 2
2013-03-06 19:11:19
Control Growth

Control of Growth
Show Answers:

  1. What is bacteriocidal?
    kills bacteria
  2. What is bacteriostatic?
    stops bacterial growth during exposure, doesn't kill it.
  3. What is sepsis?
    the presense of tissues of harmful bacteria and their toxins, typically through infection of a wound.
  4. What is asepsis?
    the absence of bacteria, viruses and other microorganisms typically during surgery.
  5. Why do number of organisms, microbial characteristics, environmental influences and time of exposure influence the effectiveness of antimicrobial treatment?
    the larger the initial population the longer it takes to eliminate them, environmental conditions may aid or inhibit elimination of microbes and the full time required by the diinfectant must be used or the entire population will not be eliminated.
  6. How are plasma membranes affected by antimicrobial agents?
    They inhibit cell wall synthesis
  7. How are proteins affected by antimicrobial agents?
    They inhibit protein synthesis
  8. How are nucleic acids affected by antimicrobial agents?
    They inhibit DNA replication and translation
  9. What methods of microbial control are bacteriostatic?
    refrigeration, freezing
  10. What methods of microbial control are physical removal?
    Filtration and soaps (hand washing)
  11. Why does dry heat take higher temperatures and longer times to sterilize than moist heat?
    Water has a higher heat capacity than air. In other words, air is a very poor conductor of heat while water is a very efficient conductor of heat.
  12. What term describes something that cannot be heat sterilized? What are some examples?
    non heat resistant...plastic, media and food
  13. Why do you have to refrigerate pasteurized milk? Is it sterile? What is the objective of pasteurization?
    It has to be refrigerated because it has been heated to steralize it and remove any microorganisms.
  14. Why are desiccation and increased osmotic pressure similar methods of microbial control?
    Because they both dehydrate cells
  15. What is the mechanism of action of ionizing radiation vs. nonionizing radiation? What is an example of each?
    Ionizing destroys DNA (xrays) and non-ionizing damages DNA (UV light)
  16. What are the principle factors in effectiveness of a disinfectant?
    Use correct disinfectant for bacteria, concentration, higher temps means greater effectiveness, application time, correct pH and is organic matter present?
  17. Describe the use of the dilution test in evaluating the effectiveness of a disinfectant
    used in industry and hospitals. Metal carriers of active bacteria are placed in disinfectant. The rings are put on media and surviving colonies are counted.
  18. Describe the use of the filter paper test in evaluating the effectiveness of a disinfectant.
    used in classrooms. disinfectant soaked filter disk is applied to petri dish with bacterial growth. Clear zone developed equals effective disinfectant.
  19. The types of disinfectants that disrupt the plasma membrane?
    phenol, phenolics, chlorhexidine, chlorine, ethanol, isopropanol, surfactants and quaternary ammonium compounds.
  20. The types of disinfectants that denature proteins?
    heavy metals
  21. The types of disinfectants that disrupt enzymatic activity?