Microbiology for Dentistry Alex Lecture Notes PDF

# MICROBIOLOGY for Dentistry Alex ## Lecture (13) : DECONTIMINATION part 1 ### Decontamination: - The process by which organisms are removed or destroyed to render an object safe. - There are three levels of decontamination: - Sterilization - Disinfection - Cleaning ### The choice of th...

# MICROBIOLOGY for Dentistry Alex ## Lecture (13) : DECONTIMINATION part 1 ### Decontamination: - The process by which organisms are removed or destroyed to render an object safe. - There are three levels of decontamination: - Sterilization - Disinfection - Cleaning ### The choice of the method of decontamination depends on: 1. The nature of the object to be decontaminated. 2. Its tolerance to the process of decontamination. 3. Its microbial load. 4. The risk it carries in transmission of infection to patients or staff in contact with the object. ### Levels Of Decontamination #### Cleaning: - The physical removal of visible soil, organic and inorganic material from objects and surfaces. - A process that eliminates many or all pathogenic microorganisms at a level that is not harmful to health and safe to handle. - This process does not necessarily include the destruction of bacterial spores. #### Disinfection: - The complete destruction or removal of microorganisms, including bacterial spores. #### Spaulding classification: - The system classifies devices as Critical, Semi Critical, or Noncritical based on the risk of contamination of a device. ##### Policy For The Decontamination Of Reusable Equipment And Devices According To The Spaulding Classification: |Risk category | level of decontamination | Examples of medical devices/items| |---|---|---| |1-Low (non-critical) | Cleaning (visibly clean)| Blood pressure cuffs, stethoscopes.| |Items in contact with intact skin | | | | 2-Intermediate (semi-critical) | Disinfection (high level)| - Respiratory equipment - Non-invasive flexible endoscopes - Bedpans. - Eg: Mirrors, reusable impression trays, and amalgam condensers | | Items in contact with mucous membranes or body fluids | | | | 3-High (critical) | Sterilization (highest level) (Critical) | 1. Surgical Instruments, 2. Implants/prostheses, 3. Rigid endoscopes, 4. Syringes, needles. | | Items involved with a break in the skin or mucous membrane or entering a sterile body cavity | | | #### WORK FLOW IN DECONTAMINATION AREA - The decontamination process should be carried out by ensuring that a dirty-to-clean workflow is maintained. This is a one-way process. ### 1. CLEANING - The physical removal of visible soil, organic and inorganic material from objects and surfaces - Removes: - all vegetative bacteria except tubercle bacilli, - all enveloped and some non-enveloped viruses, - some fungi, - but not bacterial spores. - Definition: - This is accomplished using water with detergents with or without enzymatic products. - Principles: - Environmental cleaning: Environmental surfaces are cleaned on a regular basis and when surfaces are visibly soiled. - Detergent or soap and water are adequate for cleaning surfaces in non-patient-care areas (e.g., administrative offices). - Sodium hypochlorite solutions are used after detergents in a concentration of: - 1000 ppm (1:50) - 5000 ppm (1:10) - Decontamination of critical zones e.g. Operating theaters - Decontamination of a small spill (e.g., <10 mL) of: - blood - Other potentially infectious materials (OPIM) - Decontamination of large spill (e.g., >10 mL) of: - blood - OPIM - Culture spill in the laboratory. - Cleaning of instruments and equipment - Manually: Using detergent and water - Mechanically: Using ultrasonic cleaners or washer-disinfectors. - The cleaning solutions have some disinfection properties, which put cleaning as a method of low level disinfection. - Thorough cleaning is required before intermediate or high-level disinfection and sterilization because inorganic and organic materials that remain on the surfaces interfere with the effectiveness of these processes. ### 2. DISINFECTION - Physical methods - Disinfection by moist heat at or below 100° C - Disinfection by ultraviolet radiation - Disinfection of air by filtration - Chemical methods - Low level disinfection (LLD) - Intermediate level disinfection (ILD) - High level disinfection (HLD) - **Disinfection By Moist Heat at or Below 100° C** → **Pasteurization** - Destroy all pathogenic microorganisms (Except bacterial spores) - The time-temperature relation for hot-water pasteurization is generally ~70°C for 30 minutes. - Used as alternative to chemical disinfection for: - Respiratory Therapy Equipment - Anesthesia Equipment - **Disinfection by Ultraviolet Radiation** → **UV radiation** - Low energy non-ionizing radiation - Has poor penetrating power (does not penetrate through glass or liquids) - Lethal to microorganisms under optimum conditions. - Restricted to Disinfection of previously cleaned surfaces such as: - laboratory safety cabinets - some piped water supplies - **Disinfection of Air by Filtration**→ **HEPA filters** (High-Efficiency Particle Arrester) - Rapidly free large volumes of air from infectious particles of 0.5µ size achieving efficiency of 99.99%. - Used to remove microorganisms from air - Supplied to critical sites such as: - Operating theatres (especially for orthopedics and cardiothoracic surgery) - Pharmaceutical clean rooms ### Examples of Antisepsis in healthcare settings: | | Visibly dirty hands |Visibly clean hands | | |---|---|---|---| |1-Ward staff hands|Soap and water | Alcohol based hand rubs | ILD | | 2- Surgeons' hands | 1. Alcohol, 2. Alcohol-chlorhexidine, 3. Povidone lodine | ILD | | 3- Patient's skin at operation|1. Alcohol, 2. Alcohol-chlorhexidine, 3. Povidone lodine| ILD | | 4- Patient's skin before venipuncture | 1. Alcohol, 2. Povidone lodine, 3. Alcohol chlorhexidine in case of insertion of central line | ILD | # MICROBIOLOGY for Dentistry Alex ## Lecture (14): DECONTIMINATION Part (II) ### Cont. 2. DISINFECTION #### Physical methods - Disinfection by moist heat at or below 100° С - Disinfection by ultraviolet radiation - Disinfection of air by filtration #### Chemical methods - Low level disinfection (LLD) - Intermediate level disinfection (ILD) - High level disinfection (HLD) ### III. STERILIZATION - The complete destruction or removal of microorganisms, including bacterial spores. #### A) Sterilization By Moist Heat(Autoclave) - Kills micro-organisms by coagulating and denaturing their enzymes and structural proteins. - Achieved by steaming under pressure in the autoclave, which is the most efficient and reliable method of sterilization. - When water is heated in a closed vessel under pressure the boiling point of water rises above 100°C. Raising the pressure to double atmospheric increases the boiling temperature to 121°C. - two basic types of autoclaves are - 1- Gravity Displacement Suitable for Unwrapped items. Used to sterilize non-porous articles whose surfaces have direct steam contact e.g. Dental Instruments 1- surgical instruments 2- bed linen 3- surgical dressings Cycle: 121 °C for 20 minutes - 2-Prevacuum Sterilizer Suitable for wrapped items. Used in all operating theatres for sterilization of high risk (critical items) that penetrate skin and mucosa e.g. Dental instruments 1- surgical instruments 2- bed linen 3- surgical dressings Cycle: 134 °C for 4 minutes #### B) Sterilization by dry heat - Kills by oxidation of cell constituents. - Two methods: - 1-Hot air oven The temperature of sterilization is 160°C(2 hrs) or 170°C (1 hr). - For sterilization of: - Oils - Powders - Carbon steel microsurgical instruments - Empty laboratory glassware - 2-Incineration For disposal of contaminated materials 1--Surgical dressings 2--Sharp needles 3--Clinical waste #### C) Low-Temperature Sterilization Technologies - 1-Ethylene Oxide Sterilizer Ethylene oxide (ETO) gas is microbicidal, non-corrosive, sterilent gas with high penetration power. Used in hospitals and industry to sterilize: heat-labile, single-use medical devices →prosthetic heart valves and plastic catheters. Being both toxic and highly explosive, its use is carried under controlled conditions and at temperatures below 60°C. The sterilized item must be aerated to remove the residual ethylene oxide. - Disadvantages: - Lengthy cycle time - Cost - Potential hazards to patients and staff - 2-Sterilization by y irradiation Ionizing radiations, including rays, are lethal to all cells. - Applications: - A-Large amounts of pre-packed single use items e.g. plastic syringes and catheters → (large-scale sterilization). - B- Commercial sterilization of: - Antibiotics - Hormones - Other pharmaceutical preparations - NB → The equipment and safety procedures required for sterilization by gamma rays limits its use within hospitals. - 3-Hydrogen Peroxide Gas Plasma Gas plasmas are generated in an enclosed chamber under deep vacuum to excite the gas molecules and produce charged particles in the form of free radicals. These free radicals are capable of interacting with essential cell components. The by-products of the cycle (e.g., water vapor, oxygen) are nontoxic and eliminate the need for aeration. Thus, the sterilized materials can be handled safely, either for immediate use or storage. The process operates at 37-44°C 75 minutes / cycle Used to sterilize materials and devices that cannot tolerate high temperatures and humidity Such as: - Some plastics - Electrical devices - Corrosion-susceptible tools - All articles that are sterilized by Ethylene oxide gas