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Questions and Answers
Which of the following is a physical method of sterilization?
What is the primary action of heat in heat sterilization?
At what temperature range does dry heat sterilization occur?
Which method uses boiling water or steam at atmospheric pressure for sterilization?
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Which of these materials can be treated using dry heat sterilization?
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What factor affects the efficiency of heat inactivating microorganisms?
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Which principle is used in autoclaving?
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Moist heat sterilization is primarily effective for which kind of materials?
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What is one of the main advantages of using filtration sterilization?
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Which of the following is a disadvantage of the filtration sterilization method?
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What type of filtration utilizes a porous filtration medium to retain particles?
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What is a primary mechanism of action for the gases used in chemical sterilization?
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What type of filters are specifically used for sterilizing heat-sensitive injections?
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What is the typical concentration range for ethylene oxide in sterilization processes?
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Which method of sterilization involves a risk of mutagenic and carcinogenic effects?
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Which of the following best describes membrane filters?
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What is the primary biocidal agent in sterilization that is noted for its efficiency?
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Which method is primarily capable of preventing the passage of both viable and non-viable microorganisms?
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Which application is NOT typically associated with moist heat sterilization?
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What occurs during the radiolysis of water in radiation sterilization?
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Which of the following statements regarding radiation sterilization is correct?
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What is a disadvantage of filtration sterilization?
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Which items are typically sterilized using moist heat?
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In which situation is radiation sterilization most commonly applied?
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What is a primary advantage of using dry heat for sterilization?
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What temperature range is typically used for moist heat sterilization?
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How do autoclaves achieve effective sterilization?
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Which type of radiation is capable of penetrating substances and is used for sterilization?
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What is a notable limitation of non-ionizing radiation?
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What is the effect of ionizing radiation on microorganisms?
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In what state is radiation sterilization generally applied?
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Which application is NOT suitable for UV light sterilization?
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What is the primary purpose of liquid sterilization?
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Which method of sterilization is considered more effective than liquid sterilization?
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What is a significant disadvantage of gaseous sterilization?
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In what situation is liquid sterilization most appropriate?
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Which of the following statements about heat sterilization is true?
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What types of instruments are most effectively sterilized using dry heat?
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Which of the following is a merit of gaseous sterilization?
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Which type of sterilization method is known for causing acute toxicity?
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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
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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 Sterilization:
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.
