Sterilization and Disinfection Methods
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Sterilization and Disinfection Methods

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Questions and Answers

What effect does the condensation of steam have in sterilization processes?

  • It minimizes the exposure time required for sterilization.
  • It prevents the penetration of steam into materials.
  • It generates extra heat and penetrates porous materials rapidly. (correct)
  • It reduces the temperature needed for sterilization.

    • Which of the following methods is NOT used for monitoring the sterilization process?

  • Chemical indicators
  • Biological indicators
  • Physical monitoring
  • Manual observation (correct)

    • What type of sterilization technique uses specialized chambers for specific items?

  • Chemical sterilization
  • Gamma ray sterilization (correct)
  • Moist heat sterilization
  • Filtration sterilization

    • What is the primary principle behind the use of an autoclave for sterilization?

    <p>It combines steam and high pressure to kill microorganisms.</p> Signup and view all the answers

    What is the role of biological indicators in sterilization monitoring?

    <p>They evaluate the destruction of resistant microorganisms.</p> Signup and view all the answers

    What is a limitation of UV radiation sterilization?

    <p>It has limited penetration and is effective only on exposed surfaces.</p> Signup and view all the answers

    Which of the following methods is NOT a part of moist heat sterilization?

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

    What is commonly used to monitor sterilization effectiveness in an autoclave?

    <p>Biological indicators with bacterial spores</p> Signup and view all the answers

    Which of the following techniques is specifically used for sterilizing heat-sensitive liquids?

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

    What characteristic makes bacterial spores the most resistant form of microbial life?

    <p>Their complex structure with multiple protective layers.</p> Signup and view all the answers

    Sterilization is the complete killing of all forms of microorganisms, including bacterial spores.

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

    Disinfection involves the complete destruction of all microorganisms.

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

    Incineration is a method used for the sterilization of medical and infectious waste.

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

    Moist heat sterilization includes methods like boiling and autoclaving.

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

    Bacterial spores are the most sensitive form of microbial life due to their simple structure.

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

    Boiling water at 100℃ for 10-20 minutes can kill most bacterial spores.

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

    Autoclaving uses steam under pressure to achieve sterilization.

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

    Saturated steam in an autoclave raises temperature to 121℃ for sterilization.

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

    Moist heat kills microorganisms by dehydrating them.

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

    The air in an autoclave chamber is intentionally left to allow steam penetration.

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

    The complete killing of all forms of microorganisms is called ______.

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

    The process of removing harmful vegetative microorganisms is known as ______.

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

    Methods such as boiling, pasteurization, and autoclaving are classified under ______ sterilization.

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

    Red heat and flaming are techniques used in ______ sterilization.

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

    ______ are the most resistant form of bacterial life due to their complex structure.

    <p>Bacterial spores</p> Signup and view all the answers

    Boiling in water for 10-20 minutes will kill most vegetative bacteria and inactivate some viruses, but it is ineffective against many bacterial __________.

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

    An __________ uses steam under pressure to achieve sterilization effectively.

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

    Moist heat kills microorganisms by __________ their proteins.

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

    The standard sterilization method used in hospitals is __________.

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

    The temperature of 121°C is required to kill microorganisms in an autoclave for a minimum of __________ minutes.

    <p>15</p> Signup and view all the answers

    Match the following sterilization methods with their descriptions:

    <p>Boiling = Part of moist heat sterilization that kills most bacteria Incineration = Used for disposing of medical and infectious waste Radiation = Uses ultraviolet rays for sterilization Filtration = Sterilizes heat-sensitive liquids using membrane filters</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Sterilization = The complete killing of all forms of microorganisms Disinfection = The killing or removing of harmful vegetative microorganisms Antiseptic = A disinfectant safe for living tissues Cleaning = Removing organic and inorganic materials</p> Signup and view all the answers

    Match the following dry heat sterilization techniques with their uses:

    <p>Red Heat = For sterilizing bacteriological loops Flaming = For sterilizing mouths of tubes and flasks Hot Air Oven = Used at 180°C for 30 minutes Incineration = Completely destroys organic matter and microorganisms</p> Signup and view all the answers

    Match the following physical sterilization methods with their applications:

    <p>Moist Heat = Includes boiling and autoclaving Dry Heat = Includes flaming, incineration, and hot air oven Radiation = Uses gamma rays for sterilization Filtration = Used for heat-sensitive liquids</p> Signup and view all the answers

    Match the following bacterial spore characteristics with their attributes:

    <p>Complex structure = Has multiple protective layers Most resistant = Due to the strength of their structure Bacterial Spores = Are hard to kill with standard methods Sensitive form = Not applicable to bacterial spores</p> Signup and view all the answers

    What is the primary difference between sterilization and disinfection?

    <p>Sterilization completely kills all microorganisms, including spores, while disinfection removes harmful vegetative microorganisms.</p> Signup and view all the answers

    Name two methods classified under moist heat sterilization.

    <p>Boiling and autoclaving are two methods of moist heat sterilization.</p> Signup and view all the answers

    What is the purpose of incineration in the context of sterilization?

    <p>Incineration is used to dispose of medical and infectious waste, completely destroying organic matter and microorganisms.</p> Signup and view all the answers

    At what temperature and duration is the hot air oven effective for sterilization?

    <p>The hot air oven is effective at 160°C for 2 hours or 180°C for 30 minutes.</p> Signup and view all the answers

    What characteristic of bacterial spores makes them resistant to sterilization methods?

    <p>Bacterial spores have a complex structure with multiple protective layers that make them highly resistant.</p> Signup and view all the answers

    Study Notes

    Key Definitions

    • Sterilization: Complete elimination of all microorganisms, including bacterial spores.
    • Disinfection: Killing or removal of harmful vegetative microorganisms.
    • Cleaning: Removal of organic and inorganic materials, preceding disinfection and sterilization.
    • Disinfectant: A chemical substance used for disinfection.
    • Antiseptic: A disinfectant safe for use on living tissues.

    Physical Sterilization Methods

    • Dry Heat:

      • Red Heat: Sterilizing bacteriological loops.
      • Flaming: Sterilizing mouths of tubes and flasks.
      • Incineration: Disposing of medical and infectious waste.
      • Hot Air Oven: Sterilizes at 160°C for 2 hours, 170°C for 1 hour, or 180°C for 30 minutes.

    • Moist Heat:

      • Boiling:
      • Pasteurization:
      • Autoclaving: Sterilization using steam under pressure (commonly at 121°C for 15-20 minutes), suitable for invasive procedures.

    • Radiation:

      • UV Rays: Disinfecting surfaces in laboratories, sterilizing biological safety cabinets.
      • Gamma Rays: Sterilizing disposable plastic and rubber items (gloves, syringes).

    • Filtration:

      • Used for heat-sensitive liquids.
      • Membrane filters remove microorganisms.
      • Suitable for serum, plasma, and hormones.

    Bacterial Spores

    • Structure: Complex structure with multiple protective layers.
    • Resistance: Most resistant form of bacterial life due to their structure.

    Monitoring Sterilization

    • Physical Indicators:

      • Measure time, temperature, and pressure.
      • Verify sterilization conditions.

    • Chemical Indicators:

      • Use reactive compounds to detect exposure to the sterilizing agent.

    • Biological Indicators:

      • Use spore tests to directly assess sterilization.
      • Evaluate the destruction of highly resistant microorganisms.

    Radiation Sterilization

    • UV Rays:

      • Limited penetration, effective only on exposed surfaces.
      • Expose surfaces for 15-30 minutes.

    • Gamma Rays:

      • Specialized chambers used for disposable items.

    Chemical Methods

    • Sterilization:

      • Glutaraldehyde, ethylene oxide, and phenolics can sterilize by killing spores.
      • Often used for heat-sensitive equipment.

    • Disinfection:

      • Disinfectants and antiseptics (phenolics, alcohol) kill microorganisms and reduce infection risk.

    Chemical Sterilization: Liquids

    • Chlorine Compounds:

      • Hypochlorite (bleach) decontaminates blood spills.

    • Phenolic Compounds:

      • Dettol disinfects floors and furniture.

    • Ethyl Alcohol:

      • 70% solution used as a skin antiseptic.

    Factors Influencing Disinfectant Activity

    • Temperature: Higher temperatures increase disinfectant effectiveness.
    • Contact Time: Longer contact time leads to more complete killing.
    • Concentration: Activity increases with concentration up to a point, further increases provide diminishing returns.

    Sterilization by Chemical Methods: Gases

    • Ethylene Oxide Chamber:

      • Alkylates DNA molecules to inactivate microorganisms.
      • Requires high humidity (50-60%) and temperature (55-60°C).

    • Activated Alkaline Glutaraldehyde 2%:

      • Items are immersed for 20 minutes (2-3 hours for spores).

    Review Questions

    • What are the recommended temperature, pressure, and time for autoclave sterilization?
    • Name the three types of sterilization indicators used in autoclaves.
    • Which microbial form is most resistant to sterilization and disinfection?

    Key Definitions

    • Sterilization: Eliminates all forms of microorganisms, including bacterial spores.
    • Disinfection: Killing or removing harmful vegetative microorganisms.
    • Cleaning: Removal of organic and inorganic materials.
    • Disinfectant: A chemical substance used for disinfection.
    • Antiseptic: A disinfectant safe for use on living tissues.

    Sterilization Methods

    Physical Methods

    • Dry Heat:

      • Red Heat: Sterilizes bacteriological loops.
      • Flaming: Sterilizes mouths of tubes and flasks.
      • Incineration: Disposes of medical and infectious waste, destroys all organic matter.
      • Hot Air Oven:
        • 160°C for 2 hours
        • 170°C for 1 hour
        • 180°C for 30 minutes

    • Moist Heat:

      • Boiling:
        • Kills most vegetative bacteria and inactivates viruses.
        • Ineffective against many bacterial spores and fungal spores.
        • Used for disinfections of certain metal and glass articles, not absolute sterilization.
      • Autoclaving:
        • Uses steam under pressure, similar to a pressure cooker.
        • Conditions: 121°C at double atmospheric pressure for 20-30 minutes.
        • Highly effective for sterilizing most materials.
        • Applications: culture media, surgical instruments, laboratory equipment.

    • Radiation:

      • UV Rays:
        • Used for disinfecting laboratory surfaces, including biological safety cabinets.
        • Limited penetration, effective on exposed surfaces only.
      • Gamma Rays:
        • Used for sterilizing disposable plastic and rubber items like gloves and syringes.
        • Requires specialized chambers.

    • Filtration:

      • Sterilizes heat-sensitive liquids.
      • Forced passage through a membrane filter.
      • Used for sterilizing serum, plasma, and hormones.

    Bacterial Spores

    • Structure: Complex, composed of multiple protective layers.
    • Resistance: Most challenging to kill due to their protective structure.
    • Importance: Understanding spores is essential for effective sterilization.
    • Spore Resistance Comparison: Highly resistant to most sterilization methods compared to other bacterial forms.

    Indicators of Sterilization Efficiency

    • Mechanical Indicators: Assess cycle temperature, pressure, and time by recording readings on gauges or displays.
    • Chemical Indicators: Chemical-impregnated strips or sheets that change colour when exposed to sterilizing temperatures.
    • Biological Indicators: Vials containing Bacillus Stearothermophilus (sterilizing-resistant bacteria).
      • Exposure followed by incubation allows for determination of successful sterilization.
      • No growth indicates successful sterilization.
      • Growth indicates sterilization failure.

    Chemical Methods

    Sterilization

    • Utilizes strong chemical substances that inactivate spores, often for heat-sensitive equipment:
      • Glutaraldehyde
      • Phenolics
      • Ethylene oxide

    Disinfection

    • Uses disinfectants and antiseptics to kill microorganisms and reduce infection risk:
      • Phenolics
      • Alcohol

    Chemical Sterilization: Liquids

    • Chlorine Compounds: Hypochlorite (bleach) for decontaminating blood spills.
    • Phenolic Compounds: Dettol for domestic disinfection of floors and furniture.
    • Ethyl Alcohol: 70% solution used as a skin antiseptic

    Factors Influencing Disinfectant Activity

    • Temperature:
      • Direct relationship between disinfecting activity and temperature - Higher temperatures improve effectiveness.
    • Concentration:
      • Activity increases with concentration up to a certain point.
      • Further concentration increases result in diminishing returns.
    • Contact Time:
      • Longer contact time between the disinfectant and target microorganisms allows for more complete killing.

    Sterilization by Chemical Methods: Gases

    • Ethylene Oxide Chamber:
      • Alkylates DNA to inactivate microorganisms.
      • Mixed with inert gas to prevent explosion and requires high humidity (50-60%) and temperature (55-60°C) for a 4-6 hour exposure period.
    • Activated Alkaline Glutaraldehyde 2%:
      • Items immersed for 20 minutes.
      • Immersion period increased to 2-3 hours if Mycobacterium tuberculosis or spores are present.

    Key Definitions

    • Sterilization: The complete removal or killing of all microorganisms, including bacterial spores.
    • Disinfection: The killing or removal of harmful vegetative microorganisms.
    • Cleaning: The removal of organic and inorganic materials. Cleaning precedes disinfection and sterilization.
    • Disinfectant: A chemical substance used to achieve disinfection.
    • Antiseptic: A disinfectant that can be safely used on living tissues.

    ### Sterilization Methods

    • Physical Sterilization Methods:
      • Dry Heat:
        • Red Heat: Used for sterilizing bacteriological loops.
        • Flaming: Used for sterilizing mouths of tubes and flasks.
        • Incineration:
          • Used for disposing of medical and infectious waste.
          • Examples: discarded diagnostic samples, needles, and other contaminated items.
          • Completely destroys all organic matter and microorganisms.
        • Hot Air Oven:
          • Used for sterilizing glasswares and metal instruments.
          • Temperatures and durations required:
            • 180°C for 30 minutes.
            • 170°C for 1 hour.
            • 160°C for 2 hours.
      • Moist Heat:
        • Boiling:
          • Boiling in water for 10-20 minutes will kill most vegetative bacteria and inactivate viruses.
          • Ineffective against many bacterial spores and fungal spores.
          • Used for:
            • Disinfection of certain metal articles and glasswares when absolute sterility is not required.
        • Autoclave:
          • Uses steam under pressure, similar to a pressure cooker.
          • Conditions: 121°C at double atmospheric pressure (2 bars) for 20-30 minutes.
          • Highly effective for sterilizing most materials.
          • Applications: culture media, surgical instruments, and laboratory equipment.
      • Radiation:
        • Ultraviolet (UV) Rays:
          • Used to disinfect surfaces in laboratories.
          • Sterilizes biological safety cabinets between uses.
          • Limited penetration, effective only on exposed surfaces.
        • Gamma Rays:
          • Used for sterilizing disposable plastic and rubber items like gloves and syringes.
      • Filtration:
        • Used for sterilizing heat-sensitive liquids.
        • Forced passage through a membrane filter.
        • Applications: serum, plasma, and hormones.

    Bacterial Spores

    • Spores have a complex structure with multiple protective layers.
    • Most resistant form of bacterial life due to their structure.
    • Understanding spores is crucial for effective sterilization.

    Autoclave Design and Process

    • Autoclaves are tough double-walled chambers where air is replaced by pure saturated steam under increased pressure.
    • The elevated temperature and pressure inside the autoclave (greater than 100°C) ensures complete sterilization of medical equipment and supplies.
    • The process involves:
      • Evacuation of air from the chamber to allow steam penetration.
      • Saturated steam fills the chamber, raising the temperature to 121°C for 15 minutes.
      • Steam condenses on items, releasing latent heat and facilitating penetration into porous materials.

    Monitoring Sterilization

    • Physical monitoring: Measures time, temperature, and pressure to verify sterilization conditions.
    • Chemical indicators: Use reactive compounds to detect exposure to the sterilizing agent.
    • Biological indicators: Evaluate the destruction of highly resistant microorganisms (e.g., spore tests) providing the most direct assessment of sterilization.

    Chemical Methods

    • Sterilization:
      • Strong chemicals like glutaraldehyde, phenolics, and ethylene oxide can be used to kill spores and achieve sterilization.
      • Often used for heat-sensitive equipment.
    • Disinfection:
      • Disinfectants and antiseptics (e.g., phenolics and alcohol) are used to kill microorganisms and reduce infection risk.

    Chemical Sterilization: Liquids

    • Chlorine Compounds:
      • Hypochlorite (bleach) for decontaminating blood spills.
    • Phenolic Compounds:
      • Dettol for domestic disinfection of floors and furniture.
    • Ethyl Alcohol:
      • 70% solution used as a skin antiseptic.

    Factors Influencing Disinfectant Activity

    • Temperature: Disinfectant activity is directly proportional to temperature; higher temperatures improve effectiveness.
    • Concentration: Activity increases with concentration up to an optimal point. Further increases provide diminishing returns.
    • Contact Time: Longer contact time between the disinfectant and the target allows for more complete killing of microorganisms.

    Sterilization by Chemical Methods: Gases

    • Ethylene Oxide Chamber:
      • Ethylene oxide alkylates DNA molecules to inactivate microorganisms.
      • It is mixed with an inert gas to prevent explosion and requires high humidity (50-60%) and temperature (55-60°C) with a 4-6 hour exposure period.
    • Activated Alkaline Glutaraldehyde 2%:
      • Items are immersed in this solution for 20 minutes.
      • Immersion period is extended to 2-3 hours if Mycobacterium tuberculosis or spores are present.

    Sterilization & Disinfection

    • Complete killing of all microorganisms, including spores, is sterilization.
    • Disinfection refers to killing or removing harmful vegetative microorganisms.
    • Cleaning involves removing organic and inorganic materials, preceding disinfection and sterilization.
    • Disinfectants are chemical substances for disinfection.
    • Antiseptics are disinfectants safe for living tissues.

    Sterilization Methods

    • Dry Heat: Includes red heat, flaming, incineration, and hot air oven.
      • Red heat: sterilizes bacteriological loops.
      • Flaming: sterilizes the mouths of tubes and flasks.
      • Incineration: Disposes of medical and infectious waste (discarded samples, needles, etc.)
      • Hot Air Oven: 180°C for 30 minutes, 170°C for 1 hour, or 160°C for 2 hours.
    • Moist Heat: Includes boiling, pasteurization, and autoclaving.
      • Boiling: Kills most vegetative bacteria and inactivates viruses.
      • Autoclaving: Uses steam under pressure (121°C, 2 bars, 20-30 minutes) for sterilizing most materials.
        • Effective for culture media, surgical instruments, and laboratory equipment.
        • Autoclave Design - A chamber where air is replaced with pure saturated steam under pressure.
        • Autoclave Process - Removes air, injects steam, raises temperature, and sterilizes.
    • Radiation: Uses ultraviolet rays or gamma rays for sterilization.
      • UV rays: Disinfect surfaces in laboratories, sterilize biological safety cabinets.
      • Gamma rays: Used for disposable plastic and rubber items (gloves, syringes).
    • Filtration: For heat-sensitive liquids, using membrane filters.
      • Used for serum, plasma, and hormones.

    Bacterial Spores

    • Have complex structure with multiple protective layers.
    • Most resistant form of bacterial life due to their structure.
    • Crucial for effective sterilization.

    Monitoring Sterilization

    • Physical indicators: Measure time, temperature, and pressure.
    • Chemical indicators: React to sterilizing agent, change color.
      • Paper strips/sheets.
    • Biological indicators: Assess destruction of resistant microorganisms.
      • Spore tests: Vial containing Bacillus Stearothermophilus (sterilization resistant).
        • Exposed to sterilization and incubated.
        • No growth = pass, Growth = fail.

    Chemical Methods for Sterilization and Disinfection

    • Ethylene oxide (EtO): Used for sterilizing heat-sensitive equipment.
      • Alkylates DNA molecules.
      • Requires high humidity and temperature.
    • Activated alkaline glutaraldehyde (2%): Used for disinfection.
      • Items immersed for 20 minutes (up to 2-3 for Mycobacterium tuberculosis or spores).

    Disinfection by Chemical Methods

    • Chlorine Compounds: Hypochlorite (bleach) for decontaminating blood spills.
    • Phenolic Compounds: Dettol for domestic disinfection of surfaces.
    • Ethyl Alcohol (70%): Skin antiseptic.

    Factors Influencing Disinfectant Activity

    • Temperature: Higher temperatures increase effectiveness.
    • Concentration: Activity increases up to a certain point.
    • Contact Time: Longer contact time improves effectiveness.

    Review Questions

    • Autoclave parameters: What are the recommended temperature, pressure, and time?
    • Sterilization indicators: Name the three types of indicators.
    • Most resistant microbial form: Which form is most resistant to sterilization and disinfection?

    Key Definitions

    • Sterilization: The complete elimination of all microorganisms, including bacterial spores.
    • Disinfection: The destruction or removal of harmful vegetative microorganisms.
    • Cleaning: Removal of organic and inorganic materials. This process happens before disinfection and sterilization.
    • Disinfectant: A chemical substance used to achieve disinfection.
    • Antiseptic: A disinfectant that can be safely used on living tissues.

    Sterilization Methods

    • Dry Heat: Involves methods like red heat, flaming, incineration, and hot air ovens.
      • Red Heat: Used for sterilizing bacteriological loops.
      • Flaming: Used for sterilizing the mouths of tubes and flasks.
      • Incineration: Used for disposing of medical and infectious waste, like discarded diagnostic samples, needles, and contaminated items. It completely destroys all organic matter and microorganisms.
      • Hot Air Oven: Used to sterilize dry materials like glassware, metal instruments and powders.
      • Time and Temperature: 180°C for 30 minutes, 170°C for 1 hour, or 160°C for 2 hours.
    • Moist Heat: Includes boiling, pasteurization, and autoclaving.
      • Boiling: Kills most vegetative bacteria and inactivates viruses when boiled for 10-20 minutes. However, it is ineffective against some bacterial spores and fungal spores. Commonly used for disinfecting metal articles and glassware.
      • Autoclave: Uses steam under pressure. The standard method for sterilization in hospitals.
        • Conditions: 121°C at double atmospheric pressure (2 bars) for 20-30 minutes.
        • Effectiveness: Highly effective for sterilizing most materials.
        • Applications: Used for culture media, surgical instruments, and laboratory equipment.
    • Radiation: Uses ultraviolet rays (UV) or gamma rays for sterilization.
      • UV Rays: Used to disinfect surfaces in laboratories, especially biological safety cabinets. Limited penetration, only effective on exposed surfaces.
      • Gamma Rays: Used for sterilizing disposable plastic and rubber items like gloves and syringes. Sterilization occurs in specialized gamma ray chambers.
    • Filtration: For heat-sensitive liquids. Uses membrane filters to remove microorganisms. Used for serum, plasma, and hormones.

    Spores

    • Structure: Spores are resistant due to their complex structure with multiple protective layers.
    • Resistance: Spores are the most resistant form of bacterial life.
    • Importance: Understanding spores is critical for successful sterilization.

    Autoclave Process

    • Air Evacuation: The air in the autoclave chamber is evacuated to remove oxygen, allowing steam to penetrate the items fully.
    • Steam Penetration: Saturated steam fills the sealed chamber, increasing pressure and surrounding the items to be sterilized.
    • Heat Release: The steam condenses on the items, releasing latent heat and raising the temperature to 121°C for 15 minutes to kill microorganisms.
    • Steam Penetration: The condensation also allows steam to penetrate porous materials rapidly.

    Monitoring Sterilization

    • Physical Monitoring: Measuring time, temperature, and pressure to verify sterilization conditions.
    • Chemical Indicators: Reactive compounds that change color when exposed to the sterilizing agent.
    • Biological Indicators: Spore tests to evaluate the destruction of highly resistant microorganisms.

    Chemical Methods

    • Sterilization: Chemicals that destroy spores, such as glutaraldehyde, phenolics, and ethylene oxide.
    • Disinfection: Disinfectants and antiseptics, like phenolics and alcohol are used to reduce the risk of infection.

    Chemical Sterilization: Liquids

    • Chlorine Compounds: Hypochlorite (bleach) is used for decontaminating blood spills.
    • Phenolic Compounds: Dettol is used for domestic disinfection of floors and furniture.
    • Ethyl Alcohol: 70% solution used as a skin antiseptic.

    Factors Influencing Disinfectant Activity

    • Temperature: Disinfectant activity is directly proportional to temperature. Higher temperatures improve effectiveness.
    • Concentration: Activity increases with disinfectant concentration up to an optimal point. Further increases provide diminishing returns.
    • Contact Time: Longer contact time allows for more complete killing of microorganisms.

    Chemical Sterilization: Gases

    • Ethylene Oxide Chamber: Ethylene oxide alkylates DNA molecules to inactivate microorganisms. It is mixed with an inert gas to prevent explosion and requires high humidity (50-60%) and temperature (55-60°C) with a 4-6 hour exposure period.
    • Activated Alkaline Glutaraldehyde 2%: Items are immersed in this solution for 20 minutes. Immersion time is extended to 2-3 hours if Mycobacterium tuberculosis or spores are present.

    Review Questions

    • Autoclave Parameters: What are the recommended temperature, pressure, and time for autoclave sterilization?
    • Sterilization Indicators: Name the three types of sterilization indicators used in autoclaves.
    • Most Resistant Form: Which microbial form is most resistant to sterilization and disinfection?

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    Description

    Test your knowledge on key definitions and methods of sterilization and disinfection. This quiz covers physical sterilization methods, including dry heat, moist heat, and radiation techniques. Assess your understanding of the importance of cleaning, disinfection, and antiseptic use.

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