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Control of Microbial Growth - Microbiology

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이 집합의 용어 (29)

  • What is sterilization?
    Removal or destruction of all microbial life, including endospores, usually by heat or chemical means.
  • Define disinfection.
    Destruction of most microorganisms and viruses on nonliving tissue.
  • What is the difference between antisepsis and disinfection?
    Antisepsis is the removal of microbes from living tissue, while disinfection is the destruction of microbes on nonliving surfaces.
  • What factors affect the rate of microbial death?
    Number of microbes, environment (organic matter, temperature, biofilms), time of exposure, and microbial characteristics.
  • How do antimicrobial agents damage microbial cells?
    By altering cell walls and membranes, denaturing proteins, and damaging nucleic acids.
  • What are the goals when selecting microbial control methods?
    Agents should be inexpensive, fast-acting, stable during storage, and harmless to humans, animals, and objects.
  • Which microbes are most resistant to antimicrobial agents?
    Prions and bacterial endospores are the most resistant.
  • What is the difference between high-level, intermediate-level, and low-level germicides?
    High-level kill all pathogens including endospores; intermediate kill fungal spores, protozoan cysts, viruses, and pathogenic bacteria; low-level kill vegetative bacteria, fungi, protozoa, and some viruses.
  • How does temperature affect antimicrobial efficacy?
    Higher temperatures generally increase the efficacy of antimicrobial chemicals and speed microbial death.
  • What are the four biosafety levels (BSL) in labs?
    BSL-1: nonpathogenic; BSL-2: moderate hazard; BSL-3: safety cabinets for airborne pathogens; BSL-4: handling deadly pathogens.
  • What is the thermal death point?
    The lowest temperature that kills all cells in a broth in 10 minutes.
  • Why is moist heat more effective than dry heat for microbial control?
    Because water conducts heat better, moist heat denatures proteins and destroys membranes more efficiently.
  • What are the main methods of moist heat microbial control?
    Boiling, autoclaving, pasteurization, and ultrahigh-temperature sterilization.
  • Describe autoclaving conditions.
    121ºC, 15 psi pressure, for 15 minutes to sterilize materials.
  • What is pasteurization and its purpose?
    A heat treatment to reduce pathogens and spoilage organisms in liquids without sterilization.
  • How does filtration control microbial growth?
    By physically removing microbes from liquids or air using membrane or HEPA filters.
  • What is the effect of ionizing radiation on microbes?
    It ejects electrons to create ions that damage DNA and other molecules, killing microbes.
  • How does UV radiation kill microbes?
    By causing thymine dimers in DNA, disrupting replication and transcription.
  • What are phenolics and their mode of action?
    Phenol derivatives that denature proteins and disrupt cell membranes, effective even with organic matter.
  • Why is 70% alcohol more effective than 100% alcohol as a disinfectant?
    Because water facilitates protein denaturation, making 70% alcohol more effective at killing microbes.
  • How do halogens act as antimicrobial agents?
    By denaturing enzymes and proteins, impairing protein synthesis and membrane function.
  • What are quaternary ammonium compounds (quats)?
    Low-level disinfectants that disrupt microbial membranes, used in medical and industrial applications.
  • How do heavy metals control microbial growth?
    By denaturing proteins through binding to sulfur atoms in cysteine residues.
  • What is the role of aldehydes in microbial control?
    They cross-link functional groups to denature proteins and inactivate nucleic acids, used for sterilization.
  • What are gaseous agents and their disadvantages?
    Microbicidal gases like ethylene oxide that sterilize by cross-linking proteins and DNA but are toxic and explosive.
  • What is lyophilization?
    Freeze-drying used for long-term preservation of microbial cultures by removing water and preventing ice crystal damage.
  • What is the use-dilution test?
    A method to evaluate disinfectant efficacy by exposing bacteria-coated cylinders to chemicals and checking survival.
  • How does the disk-diffusion method evaluate disinfectants?
    By measuring zones of inhibition around chemical-soaked disks placed on microbial cultures.
  • What is the impact of organic matter on disinfectant efficacy?
    Organic matter can interfere with penetration and inactivate some chemical disinfectants.