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Microbial Control and Disinfection Methods

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Terms in this set (24)

  • What is sepsis and asepsis?
    Sepsis refers to microbial contamination. Asepsis is the absence of significant contamination, often maintained by aseptic surgical techniques.
  • Who were early contributors to aseptic techniques?
    Ignatz Semmelweiss (handwashing), Florence Nightingale (battlefield aseptic techniques), and John Lister (aseptic surgery and use of phenol).
  • What is Decimal Reduction Time (DRT)?
    The time required to kill 90% of a bacterial population at a given temperature, indicating microbial death at a constant logarithmic rate.
  • List key selection criteria for antimicrobial procedures.
    Type and number of microorganisms, environmental conditions (pH, temperature, organic matter), infection risk, compatibility, residue, cost, storage, toxicity, and odor.
  • What are sterilants and how do they differ from disinfectants?
    Sterilants kill all living organisms including endospores. Disinfectants vary in level and may not kill all spores.
  • Describe the action of microbial control agents.
    They alter membrane permeability, damage proteins and nucleic acids, and disrupt energy-producing systems.
  • What is the thermal death point (TDP)?
    The lowest temperature at which all cells in a culture are killed in 10 minutes.
  • Explain Tyndallization.
    A method of intermittent boiling to destroy bacterial endospores by repeated heating and incubation cycles.
  • What is pasteurization and its types?
    A process to reduce spoilage organisms: HTST (15 sec at 72°C) and UHT (1-3 sec at 140°C) for pathogen destruction and extended storage.
  • How does an autoclave sterilize?
    Uses moist heat (steam under pressure) at 121°C and 15 PSI to denature proteins and kill all microorganisms including spores.
  • What are common dry heat sterilization methods?
    Flaming, incineration (1 sec at 1000°C), and hot-air sterilization (170°C for 2 hours).
  • Name physical methods of microbial control besides heat.
    Refrigeration, freezing, desiccation, lyophilization, filtration, osmotic pressure, ionizing and nonionizing radiation.
  • What factors affect disinfectant efficacy?
    Concentration, presence of organic matter, pH, and contact time.
  • What is the phenol coefficient?
    A measure comparing the efficacy of disinfectants to phenol, developed by Joseph Lister.
  • Describe the action and uses of phenols and phenolics.
    Denature proteins and disrupt membranes; used as disinfectants and antiseptics like Lysol and mouthwashes.
  • How do alcohols act as disinfectants?
    Denature proteins and dissolve lipids; require water and sufficient contact time; effective at 60% or higher concentration.
  • List common halogens used in microbial control.
    Chlorine (disinfectant), bromine (disinfectant), iodine (antiseptic), and fluorine (antiseptic in toothpaste).
  • What are oxidizing agents and their uses?
    Release toxic oxygen radicals to kill microbes; examples include hydrogen peroxide, peracetic acid, and ozone.
  • What are surfactants and their role?
    Surface-active agents that reduce surface tension to remove microbes; includes soaps, detergents, and quaternary ammonium compounds.
  • Explain the oligodynamic effect of heavy metals.
    Heavy metals like mercury, silver, and copper denature proteins by disrupting disulfide bonds, used as antiseptics and preservatives.
  • What are aldehydes used for in microbial control?
    Cross-link proteins and inactivate nucleic acids; used for tissue preservation and as disinfectants (glutaraldehyde, formaldehyde).
  • What are gaseous agents and their applications?
    Toxic, penetrating gases like ethylene oxide used to sterilize heat-sensitive or bulky items.
  • How are enzymes used in microbial control?
    Used to sterilize equipment contaminated with prions, such as in cases of vCJD and CJD.
  • Name common chemical food preservatives and their action.
    Organic acids (sorbic, benzoic acid) inhibit metabolism; nitrites prevent endospore germination; antibiotics like nisin prevent spoilage.