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Questions and Answers
What is the primary mechanism by which gamma rays cause damage to biological tissues?
What is the primary mechanism by which gamma rays cause damage to biological tissues?
Which of the following is NOT an advantage of using gamma rays for sterilization?
Which of the following is NOT an advantage of using gamma rays for sterilization?
Which medical devices are commonly sterilized using gamma rays?
Which medical devices are commonly sterilized using gamma rays?
What is a common application of gamma ray sterilization?
What is a common application of gamma ray sterilization?
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Which of the following statements is false regarding gamma ray sterilization?
Which of the following statements is false regarding gamma ray sterilization?
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What is the main principle of sterilization by filtration?
What is the main principle of sterilization by filtration?
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What types of substances are primarily passed through filters during sterilization by filtration?
What types of substances are primarily passed through filters during sterilization by filtration?
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How do filters work in the context of sterilization by filtration?
How do filters work in the context of sterilization by filtration?
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What outcome does sterilization by filtration achieve?
What outcome does sterilization by filtration achieve?
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Which of the following statements is true regarding the filtration process?
Which of the following statements is true regarding the filtration process?
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What is one of the main uses of sterilization in relation to antibiotics?
What is one of the main uses of sterilization in relation to antibiotics?
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What is the purpose of using membrane filters in sterilization?
What is the purpose of using membrane filters in sterilization?
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Which of the following substances is NOT typically sterilized using methods mentioned for heat-labile substances?
Which of the following substances is NOT typically sterilized using methods mentioned for heat-labile substances?
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Which of the following is a benefit of sterilizing air?
Which of the following is a benefit of sterilizing air?
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In the context of sterilization, heat-labile substances are defined as:
In the context of sterilization, heat-labile substances are defined as:
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What is a primary use of iodine in medical applications?
What is a primary use of iodine in medical applications?
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Which of the following is an application of chlorine and hypochlorite?
Which of the following is an application of chlorine and hypochlorite?
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How does iodine function as an antiseptic?
How does iodine function as an antiseptic?
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What type of chlorine is primarily used for disinfection in swimming pools?
What type of chlorine is primarily used for disinfection in swimming pools?
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In what way can iodine be described within the context of antiseptics?
In what way can iodine be described within the context of antiseptics?
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Which agent is commonly used for the disinfection of endoscopes in a microbiology lab?
Which agent is commonly used for the disinfection of endoscopes in a microbiology lab?
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Which disinfectant is typically recommended for cleaning blood spills?
Which disinfectant is typically recommended for cleaning blood spills?
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What is the preferred disinfectant used for maintaining swimming pool water quality?
What is the preferred disinfectant used for maintaining swimming pool water quality?
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Which disinfectant is most appropriate for surgical skin preparation?
Which disinfectant is most appropriate for surgical skin preparation?
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Which chemical compound serves as an effective high-level disinfectant for heat-sensitive medical instruments?
Which chemical compound serves as an effective high-level disinfectant for heat-sensitive medical instruments?
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What is the effective contact time for sodium hypochlorite when used as a blood spill disinfectant?
What is the effective contact time for sodium hypochlorite when used as a blood spill disinfectant?
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Which concentration of alcohol is recommended for use in various disinfecting applications?
Which concentration of alcohol is recommended for use in various disinfecting applications?
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Which of the following is NOT a use for alcohol according to the content?
Which of the following is NOT a use for alcohol according to the content?
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For which medical equipment is alcohol specifically stated to be used for disinfection?
For which medical equipment is alcohol specifically stated to be used for disinfection?
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What is a characteristic of sodium hypochlorite in relation to surfaces?
What is a characteristic of sodium hypochlorite in relation to surfaces?
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Study Notes
Sterilization and Disinfection
- Sterilization is the process of destroying all microbial life, including spores.
- Disinfection reduces the number of microbes on a nonliving surface, making it safe for use.
- Antiseptics are chemicals that reduce microbes on living tissue.
- Cleaning removes visible dirt from objects and surfaces using water and detergents. Cleaning is crucial before disinfection and sterilization.
Organisms Resistance to Sterilization
- Organisms resist sterilization to varying degrees.
- The order of resistance (from most to least resistant) is:
- Prions
- Bacterial spores
- Mycobacteria
- Nonenveloped viruses
- Fungi
- Bacteria
- Enveloped viruses
Methods of Sterilization
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Physical methods include:
- Radiation: Gamma rays are highly penetrating and effective at low temperatures. Used for transplant devices, medical devices, etc.
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Heat:
- Dry heat: Hot air ovens, flaming, incineration. Effective for glassware, metals, dry materials.
- Moist heat: Autoclaves use pressurized steam to sterilize heat- and moisture-resistant items such as surgical instruments, gowns, linens, etc.
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Chemical methods include:
- Sterilant Gases: Ethylene oxide is used for heat and moisture-sensitive devices (e.g., sutures, catheters, endoscopes), but it's flammable, toxic, and requires aeration time to eliminate residues.
Dry Heat Sterilization
- Red heat: Used for metals like forceps.
- Flaming: Used for sterilizing mouth/parts of tubes, glass slides
- Hot air oven: Used to sterilize glassware, metals, and dry materials. Optimal conditions: 150°C for 150 minutes, 160°C for 120 minutes, or 170°C for 60 minutes.
Autoclave (Moist Heat)
- Uses saturated steam under pressure to raise the boiling point above 100°C.
- Effective for heat- and moisture-resistant items.
- Three key parameters: temperature, time, and pressure.
- Standard cycle: 15 minutes at 121°C with 15 pounds pressure.
- Flash cycle: 134°C for 3-10 minutes for emergencies; Prions require 134°C for 60 minutes.
Hot Air Oven
- Electrically heated, controlled by thermostat.
- Optimal sterilization conditions: 150°C for 150 minutes, 160°C for 120 minutes, or 170°C for 60 minutes.
- Used for glassware (good quality), metals, and dry materials like oil and powders.
- Spores of Bacillus atrophaeus are used as a sterilization control.
Monitoring Autoclave Sterilization
- Physical monitoring: Checks cycle time, temperature, and pressure.
- Biological monitoring: Uses spores of Geobacillus stearothermophilus.
Ionizing Radiation (Gamma Rays)
- Mechanism: Ionization breaks DNA.
- Advantages: High penetrating power, cold sterilization.
- Uses: Transplant devices, packaged medical devices (syringes, surgical gloves, catheters).
Sterilization by Filtration
- Principle: Removes microorganisms by passing through filters with small pores.
- Uses: Sterilizing fluids containing heat-sensitive substances (antibiotics, vaccines), and sterilizing air.
- Membrane Filters: Used for fluids and air. Bacteria filters use 0.22–0.45µm pore size, while Viral filters use smaller pores. Filters are used in surgical masks and respirators, in HEPA filters (used in surgical rooms, ICUs, and safety cabinets), and in air sterilization.
Chemical Methods (Sterilization by Gases)
- **Ethylene Oxide:** Used for heat and moisture-sensitive devices, but requires aeration to remove residue (8-12 hours). It's flammable and toxic.
Disinfection by Physical Methods
- UV radiation: Effective for denaturing DNA; but poor penetration and requires long exposure times. Used in operating theatres, biological safety cabinets, and isolation room surfaces.
Disinfection by Moist Heat
- Boiling: 100°C for 15 minutes.
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Pasteurization: Used for milk and other drinks using methods like:
- Batch method: 63°C for 30 minutes, followed by rapid cooling.
- Flash method: 72°C for 15 seconds, followed by rapid cooling. Examples include Mycobacterium bovis and Brucella spp.
Methods of Chemical Disinfection
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High-level disinfectants: Can kill bacterial spores (Aldehydes, H2O2).
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Intermediate-level disinfectants: Kill all organisms except spores (Alcohol, Halogens).
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Low-level disinfectants: Kill limited organisms (Phenols).
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Halogens (e.g., iodine, chlorine, sodium hypochlorite): Used as antiseptics for wound cleaning and surgical prep, and as disinfectants for water supplies, swimming pools, and surface spills.
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Alcohol: Used in various concentrations (70–80%) for handrubs, and cleaning of stethoscopes and ultrasound machines.
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Phenols: Used as antiseptics (e.g., Dettol) and disinfectants for environmental surfaces like bedside tables.
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Aldehydes (e.g., glutaraldehyde, formaldehyde): Glutaraldehyde are strong disinfectants, effective against bacterial spores, and used to sterilize endoscopes and microbiology lab surfaces. Formaldehyde is used for preservation of anatomical specimens, but it's limited due to fumes and potential carcinogenicity.
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Hydrogen Peroxide: Used for contact lenses and wound cleaning.
Factors Affecting Disinfection and Sterilization
- Agent concentration/stability
- Number and type of microorganisms
- Temperature and pH
- Organic or interfering substances
- Physical characteristics of the object
- Presence of biofilms
Test Your Knowledge Answers (Matching)
- Provided in the slides.
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Description
Test your knowledge on gamma ray sterilization and the filtration process. This quiz covers mechanisms, advantages, medical applications, and principles of sterilization techniques. Enhance your understanding of how these methods are utilized in various medical settings.
