Sterilization and Disinfection PDF

Sterilization & Disinfection An overview of the crucial processes for maintaining a safe and sterile medical environment. by Heba Rashed  Learning Objectives 1 Key Definitions Memorize important terms related to sterilization. 2 Sterilization Methods Outline different techniques and...

Sterilization & Disinfection An overview of the crucial processes for maintaining a safe and sterile medical environment. by Heba Rashed  Learning Objectives 1 Key Definitions Memorize important terms related to sterilization. 2 Sterilization Methods Outline different techniques and their applications. 3 Item Compatibility Recognize which items are suitable for each sterilization method.  Definitions Sterilization Disinfection The complete killing of all forms of The killing or removing of harmful vegetative microorganisms, including bacterial spores. microorganisms. Cleaning Removing organic and inorganic materials. Precedes Disinfectant disinfection and sterilization. A chemical substance used to achieve disinfection. Antiseptic A disinfectant that can be safely used on living tissues.  Physical Sterilization Methods Dry Heat Includes red heat, flaming, incineration, and Moist Heat hot air oven. Includes boiling, pasteurization, and autoclaving Radiation Uses ultraviolet rays or gamma rays for sterilization. Filtration For heat-sensitive liquids, using membrane filters. Dry Heat: Red Heat and Flaming Red Heat Flaming Used for sterilizing bacteriological loops. For sterilizing mouths of tubes and flasks. Dry Heat: Incineration 1 Purpose Used for disposing of medical and infectious waste. 2 Examples Discarded diagnostic samples, needles, and other contaminated items. 3 Effectiveness Completely destroys all organic matter and microorganisms. Dry Heat: Hot Air Oven 180°C 160°C for 30 for 2 minut hours es 170°C for 1 hour Bacterial Spores Structure 1 Spores have a complex structure with multiple protective layers. 2 Resistance Most resistant form of bacterial life due to their structure. Importance 3 Understanding spores is crucial for effective sterilization. Moist Heat: Boiling (At 100 ℃) 10 mins Principal: Boiling in water for 10-20 minutes will kill most vegetative bacteria and inactivate viruses. However boiling is ineffective against many bacterial as Staphylococcal enterofoxin and fungal spores. Used for: When absolute sterility is not required, certain metal articles and glass wares can be disinfected by placing them in boiling water for 10-20 minutes Moist Heat: Autoclave Principle Uses steam under pressure, similar to a pressure cooker. 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. Moist Heat Autoclaving Autoclave Design Moist Heat Sterilization Autoclaving is the standard sterilization The autoclave is a tough double-walled Moist heat kills microorganisms by method in hospitals, using an autoclave chamber where air is replaced by pure denaturing their proteins. The elevated machine that works on the same principle as a saturated steam under increased pressure, temperature and pressure inside the autoclave pressure cooker to generate moist heat above allowing the water to boil at temperatures ensures complete sterilization of medical 100°C. greater than 100°C. equipment and supplies.  Autoclave Images Autoclaves are widely used in healthcare facilities and Autoclaves come in various sizes and designs to meet laboratories for sterilization of medical instruments, equipment, the needs of different settings, from small benchtop and supplies. They use moist heat in the form of pressurized units to large-capacity floor models. steam to kill microorganisms effectively.  Autoclave Process The air in the chamber is evacuated to remove oxygen and allow the steam to fully penetrate the items. Saturated steam fills the tightly sealed chamber, increasing the pressure and surrounding the items to be sterilized. The steam condenses on the items, releasing latent heat and raising the temperature to 121°C for 15 minutes to kill microorganisms. Temp. > 100 C therefore spores killed. Condensation of steam generates extra heat. The condensation also allows the steam to penetrate rapidly into porous materials. Note: for all invasive procedures at operating room or clinics, autoclavable equipments should be used.  Monitoring Methods Monitoring the sterilization process is crucial to ensure the efficacy of the method. Various monitoring techniques are used, including physical, chemical, and biological indicators. Physical monitoring involves measuring parameters like time, temperature, and pressure to verify the sterilization conditions. Chemical indicators use reactive compounds to detect exposure to the sterilizing agent. Biological indicators, such as spore tests, provide the most direct assessment of sterilization by evaluating the destruction of highly resistant microorganisms. Indicators of sterilization efficiency 1.Mechanical indicators: Assess cycle’s temperature, pressure, time By noting gauges or displays Indicators of sterilization efficiency 2.Chemical indicators: ▷ Chemical-impregnated paper strips or sheets ▷ Change color when exposed to high temperatures enough for sterilization Indicators of sterilization efficiency 3.Biological indicators: Vial containing Bacillus Stearothermophilus (sterilization resistant) ▷ Exposed to sterilization & incubated oNo Growth = pass o Growth = fail  Radiation Sterilization: UV Rays 1 Application Used to disinfect surfaces in laboratories. 2 Specific Use Sterilizes biological safety cabinets between uses. 3 Limitation Expose surfaces for recommended Limited penetration, effective only on exposed time, typically 15-30 minutes surfaces. Radiation Sterilization: Gamma Rays Equipment Applications Specialized chambers for Used for disposable plastic and rubber items like gamma ray sterilization. gloves and syringes. Filtration Sterilization Purpose Sterilizes heat-sensitive liquids. Method Forced passage through a membrane filter. Applications Used for serum, plasma, and hormones. Review Questions 1 Autoclave Parameters What are the recommended temperature, pressure, and time for autoclave sterilization? 2 Sterilization Indicators Name the three types of sterilization indicators used in autoclaves. 3 Most Resistant Form Which microbial form is most resistant to sterilization and disinfection?  Chemical Methods Sterilization Disinfection Some strong chemical substances, Disinfectants and antiseptics, like such as glutaraldehyde and phenolics and alcohol, are used for ethylene oxide, can be used to disinfection purposes to kill achieve sterilization by killing microorganisms and reduce the risk spores. These are often utilized for of infection. heat-sensitive equipment. 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 Activity of Disinfectants Temperature Disinfectant activity is directly Contact Time proportional to temperature - higher Longer contact time between the temperatures improve the Concentration disinfectant and the target allows for effectiveness. more complete killing of Activity increases with concentration microorganisms. up to an optimal point. Further increases in concentration provide diminishing returns. Sterilization by Chemical Methods : Gases Ethylene Oxide Chamber Activated Alkaline Glutaraldehyde 2% Ethylene oxide alkylates DNA molecules to inactivate Items are immersed in this solution for 20 minutes. If microorganisms. It is mixed with an inert gas to prevent explosion, Mycobacterium tuberculosis or spores are present, the immersion and requires high humidity (50-60%) and temperature (55-60°C) period is extended to 2-3 hours. with a 4-6 hour exposure period. Hospital Disinfection Methods Floors and Walls Surfaces and Tables Hands and Skin Phenolic disinfectant solutions at 1- Hypochlorite solutions and alcohol- Chlorhexidine, iodine, and 70% 2% concentration are effective for based disinfectants are commonly alcohol are used to disinfect disinfecting floors and walls in used to disinfect hospital surfaces surgeons' hands and patients' skin. hospitals. and tables. Endoscopes Thermometers Endoscopes are disinfected using 2% glutaraldehyde Thermometers can be disinfected using 70% alcohol (Cidex) solutions and subatmospheric steam sterilization. solutions. Thank you