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Indietro

chapter 7

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Termini in questo insieme (20)

  • Define sterilization.

    Sterilization is the removal and destruction of all microbial life, including endospores.

  • What is disinfection?

    Disinfection is the destruction of harmful microorganisms on inanimate surfaces or environments.

  • Explain antisepsis.

    Antisepsis is the destruction of harmful microorganisms from living tissue.

  • What is degerming?

    Degerming is the mechanical removal of microbes from a limited area, such as skin around an injection site.

  • Define sanitization.

    Sanitization lowers microbial counts on eating utensils or surfaces to safe public health levels.

  • What is a biocide or germicide?

    Biocide or germicide refers to treatments that kill microbes.

  • Define bacteriostasis.

    Bacteriostasis is the inhibition of microbial growth without killing the microbes.

  • What does asepsis mean?

    Asepsis is the absence of significant contamination by microbes.

  • Describe the microbial death curve.

    Microbial death occurs exponentially; a constant percentage of the population dies per unit time, shown as a straight line on a logarithmic scale.

  • What factors affect the effectiveness of microbial control agents?

    Factors include the number of microbes, environment (organic matter, temperature, biofilms), time of exposure, and microbial characteristics (e.g., endospores).

  • How do microbial control agents damage cells?

    They damage the plasma membrane causing leakage, damage proteins (enzymes), and damage nucleic acids.

  • Compare moist heat and dry heat sterilization.

    Moist heat denatures proteins and is faster (e.g., autoclaving), while dry heat kills by oxidation and requires higher temperatures and longer times.

  • What is the autoclave sterilization condition?

    Steam under pressure at 121°C and 15 psi for 15 minutes kills all organisms except prions and endospores.

  • How does pasteurization differ from sterilization?

    Pasteurization reduces spoilage organisms and pathogens but does not sterilize; UHT pasteurization sterilizes milk by heating to 140°C for 4 seconds.

  • What is filtration used for in microbial control?

    Filtration removes microbes from heat-sensitive liquids or air using membrane filters (0.22 μm) or HEPA filters (0.3 μm).

  • How do low temperatures control microbial growth?

    Low temperatures have a bacteriostatic effect by slowing metabolism; includes refrigeration, deep-freezing, and lyophilization.

  • Explain how radiation kills microbes.

    Ionizing radiation creates hydroxyl radicals that damage DNA; nonionizing UV radiation causes thymine dimers in DNA, disrupting replication.

  • What is the use-dilution test?

    It evaluates disinfectant effectiveness by exposing bacteria-coated cylinders to disinfectants and then culturing to check survival.

  • Describe the disk-diffusion method.

    Filter paper disks soaked in chemicals are placed on bacterial cultures; zones of inhibition indicate antimicrobial effectiveness.

  • List factors that influence effective disinfection.

    Concentration of disinfectant, presence of organic matter, pH, temperature, and time of exposure.