Sterilization and Disinfection Lecture Notes PDF

‫كلية الطب‬ Sterilization & Disinfection (Lectures 15 & 16) Dr. Sozan Mohamed Fadl Head of Microbiology & Immunology Unit Organisms According to Increasing level of Resistance to Sterilization...

‫كلية الطب‬ Sterilization & Disinfection (Lectures 15 & 16) Dr. Sozan Mohamed Fadl Head of Microbiology & Immunology Unit Organisms According to Increasing level of Resistance to Sterilization Prions Bacterial Mycobacteria spores Nonenveloped viruses Fungi Bacteria Enveloped viruses  Definitions Sterilization: The process of destroying or eliminating all microbial life, including spores. Disinfection: The process of reducing the number of microbes from a nonliving surface or object leaving them safe for use. Antiseptics: Chemicals used to reduce the number of microbes on a living tissue. Cleaning: the removal of visible dirt (organic & inorganic material) from objects and surfaces using water with detergents. Cleaning is essential before disinfection and sterilization.  Sterilization Physical Chemical Sterilant Radiation Heat Filtration Gas Gamma Ethylene Dry Moist Liquid Air Rays Oxide (HEPA) Hot air Autoclave oven  Dry Heat Sterilization Hot air Red heat Flaming Incineration Oven Mouth of Disposable Metals e.g., Glassware, tubes, glass items & forceps metals. slides waste.  Hot Air Oven Electrically heated (with thermostat to control temp.) Optimum conditions for sterilization: – 150 °C for 150 minutes. – 160 °C for 120 minutes. – 170 °C for 60 minutes. Used for Sterilization of: Glassware (good quality), metals, dry material (oil, powders) Sterilization control: Spores of Bacillus atrophaeus  Autoclave (Moist Heat ) Use saturated steam under pressure to raise the boiling temperature above 100 0C. Uses: Heat and moisture resistant items: surgical & dental instruments, gowns, linens, culture media. Three parameters are important: temperature, time & pressure. Sterilization Cycles: - Standard use: 15 minutes at 121°C. at pressure of 15 pounds (lbs). - Flash Sterilization used at emergency: 134°C for 3-10 minutes. - Prions: 134°C for 60 minutes Hospital Autoclave: Wrapping before sterilization Monitoring Efficiency of Autoclave Sterilization: 1- Physical: Cycle time, temperature, and pressure. 2- Biological: Spores of Geobacillus stearothermophilus.  Ionizing Radiation (Gamma Rays) Mechanism: ionization leads to breakage of DNA Advantages: high penetrating, low temperature (cold sterilization) Use: transplant devices (e.g., cardiac valves), packaged disposable medical devices (syringes, surgical gloves, vascular & urinary catheters,).  Sterilization by Filtration Principle: removing microorganisms (not killing) from fluids and air by passing them through filters with pores so small that bacteria and viruses are arrested. Uses: 1- Sterilization of fluids that contain heat-labile substances: antibiotics & vaccines. 2- Sterilization of air.  Membrane filters: Retain all the particles larger than their pore size. o Bacterial filters have 0.22-0.45 μm pore size. o Viral filters have smaller pore size. o Used for fluids and air.  Filtration of Air Surgical (3-ply) mask and respirators. ™HEPA filters (High Efficiency Particulate Air filter): – Used in the surgical rooms, ICUs, isolation rooms and safety cabinet in microbiology laboratories. HEPA Filters  Chemical Methods: Sterilization by Gases Ethylene Oxide: Uses: Heat and moisture sensitive devices: Sutures, catheters, endoscopes, etc. Disadvantages: inflammable & toxic; needs aeration of the sterilized materials for 8–12 hours to remove residual ETO.  Disinfection Physical Chemical Radiation Heat Liquids Intermedi Moist High Low ate UV Rays - Boiling - Pasteurization  Disinfection by Radiation Ultraviolet Radiation: Denatures the DNA. Need long-term exposure and its penetration power is poor. Uses: Operating theatres. Biologic safety cabinets. Isolation rooms surfaces.  Disinfection by Moist Heat A. Boiling: At 100C for 15 minutes. B. Pasteurization: Uses: milk and other drinks. Examples: Mycobacterium bovis, Brucella spp. - Batch method: 63°C for 30 minutes followed by rapid cooling - Flash method: 72°C for 15 seconds followed by rapid cooling.  Chemical Disinfectant Intermediate High level Low level level disinfectant disinfectant disinfectant Can kill the Kill all Kill limited bacterial organisms type of spores except spores organisms -Aldehydes - Alcohol - Phenol -H2O2 - Halogens  High Level Disinfectant 1) Aldehyde: A. Glutaraldehyde: - Disinfectant: 2% or 2.4% concentration for 20 minutes. - Sterilant: 2% or 2.4% for 10-14 hours. - Uses: endoscopes and microbiology lab surfaces. B. Formaldehyde: - Limited use because of its irritating fumes and odor. It is also a potential carcinogen. - Restricted to nonpatient care area only; preservation of anatomical specimen. 2) Hydrogen Peroxide (H2O2): o Used for contact lens and for wound cleaning  Intermediate Level Disinfectant 1) Halogens: A. Iodine: - Antiseptics: wound cleaning, surgical skin preparation B. Chlorine and Hypochlorite: - Free chlorine: disinfection of water supplies and swimming pools. - Sodium hypochlorite: blood spill (10–20 minutes), surface disinfectant. 2) Alcohol: o Concentration: 70–80% is used for various purposes o Uses: handrub, stethoscopes, ultrasound machines, surfaces.  Low Level Disinfectant 1) Phenolics – Used as antiseptics: chloroxylenol (Dettol). – Disinfectants: Environmental surfaces (e.g., bedside tables, and laboratory surfaces). Factors that affect disinfection and sterilization: 1- The concentration and stability of the agent. 2- The number and the type of microorganisms. 3- The temperature and pH. 4- The presence of organic or other interfering substances. 5- Physical nature of the object (e.g., hinges, and lumens) 6- Presence of biofilms.  Test Your Knowledge Match the objects with the correct method 1) Gloves, cardiac valves A. Hot air oven B. Autoclave 2) Endoscopes C. UV rays 3) Culture media, Gowns D. Ethylene oxide 4) Powders, oils E. Ionizing radiation 5) Heat sensitive liquids F. Membrane filters 6) Isolation rooms 1---E 2---D 3---B 4---A 5---F 6---C  Test Your Knowledge Match the objects with the correct method 1) Contact lenses A. Free chlorine 2) Endoscopes/ Microbiology lab B. Sodium hypochlorite 3) Blood spills C. Alcohol 4) Swimming pools D. Glutaraldehyde 5) Surgical skin preparation E. Hydrogen peroxide (H2O2) 6) Stethoscopes F. Iodine 1---E 2---D 3---B 4---A 5---F 6---C  References Essentials of Medical Microbiology, 3rd edition, section 3, pages 252-263. https://www.cdc.gov/infectioncontrol/guideline s/disinfection/introduction.html