Methods of Sterilization in Microbiology
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Questions and Answers

Which of the following is a physical method of sterilization?

  • Chemical disinfection
  • Filtration method (correct)
  • Ultraviolet treatment
  • Gaseous method
  • What is the primary action of heat in heat sterilization?

  • Evaporation of moisture
  • Destruction of physical structure
  • Induction of lethal chemical events (correct)
  • Neutralization of pathogens
  • At what temperature range does dry heat sterilization occur?

  • 200-220˚C
  • 160-180˚C (correct)
  • 100-120˚C
  • 80-100˚C
  • Which method uses boiling water or steam at atmospheric pressure for sterilization?

    <p>Moist heat sterilization</p> Signup and view all the answers

    Which of these materials can be treated using dry heat sterilization?

    <p>Non-aqueous thermo stable liquids</p> Signup and view all the answers

    What factor affects the efficiency of heat inactivating microorganisms?

    <p>Degree of heat and exposure time</p> Signup and view all the answers

    Which principle is used in autoclaving?

    <p>Dry saturated steam under pressure</p> Signup and view all the answers

    Moist heat sterilization is primarily effective for which kind of materials?

    <p>Thermo stable products</p> Signup and view all the answers

    What is one of the main advantages of using filtration sterilization?

    <p>It leaves no chemical residue.</p> Signup and view all the answers

    Which of the following is a disadvantage of the filtration sterilization method?

    <p>It requires specialized equipment.</p> Signup and view all the answers

    What type of filtration utilizes a porous filtration medium to retain particles?

    <p>Depth filters</p> Signup and view all the answers

    What is a primary mechanism of action for the gases used in chemical sterilization?

    <p>Alkylation of proteins and nucleic acids</p> Signup and view all the answers

    What type of filters are specifically used for sterilizing heat-sensitive injections?

    <p>Sterilizing grade filters</p> Signup and view all the answers

    What is the typical concentration range for ethylene oxide in sterilization processes?

    <p>800-1200 mg/L</p> Signup and view all the answers

    Which method of sterilization involves a risk of mutagenic and carcinogenic effects?

    <p>Chemical sterilization with gaseous agents</p> Signup and view all the answers

    Which of the following best describes membrane filters?

    <p>They can be made of porous materials about 0.1 mm thick.</p> Signup and view all the answers

    What is the primary biocidal agent in sterilization that is noted for its efficiency?

    <p>Moist heat</p> Signup and view all the answers

    Which method is primarily capable of preventing the passage of both viable and non-viable microorganisms?

    <p>Filtration sterilization</p> Signup and view all the answers

    Which application is NOT typically associated with moist heat sterilization?

    <p>Plastics</p> Signup and view all the answers

    What occurs during the radiolysis of water in radiation sterilization?

    <p>Chemical changes happen</p> Signup and view all the answers

    Which of the following statements regarding radiation sterilization is correct?

    <p>It is effective for heat sensitive products.</p> Signup and view all the answers

    What is a disadvantage of filtration sterilization?

    <p>Does not remove chemical contaminants</p> Signup and view all the answers

    Which items are typically sterilized using moist heat?

    <p>Surgical instruments and ophthalmic preparations</p> Signup and view all the answers

    In which situation is radiation sterilization most commonly applied?

    <p>For heat sensitive products</p> Signup and view all the answers

    What is a primary advantage of using dry heat for sterilization?

    <p>It effectively eliminates bacterial endotoxins.</p> Signup and view all the answers

    What temperature range is typically used for moist heat sterilization?

    <p>121-134˚C</p> Signup and view all the answers

    How do autoclaves achieve effective sterilization?

    <p>By flushing steam to remove air from the chamber.</p> Signup and view all the answers

    Which type of radiation is capable of penetrating substances and is used for sterilization?

    <p>Ionizing radiation</p> Signup and view all the answers

    What is a notable limitation of non-ionizing radiation?

    <p>It primarily sterilizes surfaces rather than penetrating materials.</p> Signup and view all the answers

    What is the effect of ionizing radiation on microorganisms?

    <p>It damages DNA, resulting in cell death.</p> Signup and view all the answers

    In what state is radiation sterilization generally applied?

    <p>In the dry state</p> Signup and view all the answers

    Which application is NOT suitable for UV light sterilization?

    <p>Sterilizing pharmaceutical dosage forms</p> Signup and view all the answers

    What is the primary purpose of liquid sterilization?

    <p>To kill all viable microorganisms and their spores</p> Signup and view all the answers

    Which method of sterilization is considered more effective than liquid sterilization?

    <p>Gaseous sterilization</p> Signup and view all the answers

    What is a significant disadvantage of gaseous sterilization?

    <p>Gases are potentially mutagenic alkylating agents.</p> Signup and view all the answers

    In what situation is liquid sterilization most appropriate?

    <p>When a low level of contamination is present</p> Signup and view all the answers

    Which of the following statements about heat sterilization is true?

    <p>Moist heat is more effective than dry heat.</p> Signup and view all the answers

    What types of instruments are most effectively sterilized using dry heat?

    <p>Glassware and metal surgical instruments</p> Signup and view all the answers

    Which of the following is a merit of gaseous sterilization?

    <p>It is a reliable method for heat-sensitive devices.</p> Signup and view all the answers

    Which type of sterilization method is known for causing acute toxicity?

    <p>Gaseous sterilization</p> Signup and view all the answers

    Study Notes

    Sterilization

    • The process of eliminating transmissible agents from surfaces, equipment, foods, medications or biological culture media.

    Methods of Sterilization

    • Physical: Thermal (heat), radiation, filtration
    • Chemical: Gaseous

    Physical Methods: Heat

    • Heat is the most widely used and reliable sterilization method.
    • Dry Heat: 160-180°C for up to 2 hours, for thermo stable products (glassware, metal surgical instruments, non-aqueous thermo stable liquids and powders).
    • Moist Heat: 121-134°C using steam under pressure, for moisture-resistant materials and is the most dependable method for decontamination of laboratory waste and sterilization of laboratory glassware, media, and reagents.
    • Autoclave: uses pressurized steam to destroy microorganisms.

    Thermal (Heat) Methods

    • Thermal methods include:
      • Dry Heat Sterilization:
        • Flaming, incineration, hot air oven
      • Moist Heat Sterilization:
        • Boiling water/ steam at atmospheric pressure
        • Hot medium below boiling point (Pasteurization)
        • Dry saturated steam – Autoclaving

    Dry Heat

    • Employ higher temperatures (160-180°C) and requires an exposure time of up to 2 hours.
    • Benefits include good penetrability and non-corrosive nature.
    • Destroys bacterial endotoxins.

    Moist Heat

    • Uses steam in the range of 121-134°C.
    • Saturated steam is an effective sterilizing agent.

    Radiation Sterilization

    • Uses ionizing radiation (gamma or X-rays) to destroy microorganisms by damaging their DNA.
    • Non-ionizing radiation (UV light) is used for surface sterilization.
    • Advantages include:
      • No degradation of media during sterilization.
      • Leaves no chemical residue.
      • Precise and uniform dosage distribution.
      • Immediate availability of media after sterilization.
    • Disadvantages:
      • More costly than heat sterilization.
      • Requires specialized equipment.

    Filtration Sterilization

    • Removes microorganisms and does not destroy them.
    • Used for both clarification and sterilization of liquids and gases.
    • Major mechanisms: sieving, adsorption, trapping within the filter material.
    • Employed for heat sensitive injections and ophthalmic solutions, biological products, and air and other gases for supply to aseptic areas.
    • Types:
      • Depth filters use a porous filtration medium to retain particles throughout the media.
      • Membrane filters are porous membranes made of cellulose acetate, cellulose nitrate, polycarbonate, polyvinylidene fluoride, or some other synthetic materials.

    Chemical Sterilization Method

    Gaseous Method

    • Chemically reactive gases like formaldehyde and ethylene oxide possess biocidal activity.
    • Mechanism of action is through alkylation of proteins and nucleic acids.
    • Ethylene oxide is commonly used to process heat-sensitive devices.
    • Both gases are potentially mutagenic and carcinogenic and produce acute toxicity.

    Liquid Sterilization

    • Involves submerging equipment in a liquid sterilant to kill all viable microorganisms and their spores.
    • Not as effective as gaseous sterilization, but appropriate for low contamination levels.

    Importance of Sterilization

    • Moist heat sterilization is the most efficient biocidal agent, commonly used for many items.

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    Description

    Explore the various methods of sterilization used in microbiological practices. Learn about physical methods like dry and moist heat, as well as chemical methods. This quiz covers the principles and applications of these essential sterilization techniques.

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