Sterilization

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Sterilization,AIMST

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3/21/2012 Sterilization principles

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3/21/2012 Sterilization can be defined as any process that effectively kills or eliminates transmissible agents (such as fungi, bacteria, viruses) from a surface, equipment, foods, medications, or biological culture medium. In practice sterility is achieved by exposure of the object to be sterilized to chemical or physical agent for a specified time. Various agents used as steriliants are: elevated temperature, ionizing radiation, chemical liquids or gases etc. The success of the process depends upon the choice of the method adopted for sterilization. Introduction Sterilization destroys all microorganisms, including bacterial endospores ..

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3/21/2012

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3/21/2012 Pharmaceutical Importance of Sterilization Moist heat sterilization is the most efficient biocidal agent. In the pharmaceutical industry it is used for: Surgical dressings, Sheets, Surgical and diagnostic equipment, Containers, Closures, Aqueous injections, Ophthalmic preparations etc . .. Dry heat sterilization can only be used for thermo stable, moisture sensitive or moisture impermeable pharmaceutical and medicinal . These include products like; Dry powdered drugs, Suspensions of drug in non aqueous solvents, Oils, fats waxes, soft hard paraffin silicone, Oily injections, implants, ophthalmic ointments and ointment bases etc .

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3/21/2012 Gaseous sterilization is used for sterilizing thermolabile substances like; hormones, proteins, various heat sensitive drugs etc. U.V light is perhaps the most lethal component in ordinary sunlight used in sanitation of garments or utensils . Gamma-rays from Cobalt 60 are used to sterilize antibiotic, hormones, sutures, plastics and catheters etc. Filtration sterilizations are used in the treatment of heat sensitive injections and ophthalmic solutions, biological products, air and other gases for supply to aseptic areas. They are also used in industry as part of the venting systems on fermentors , centrifuges, autoclaves and freeze driers .

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3/21/2012 When exposed to a killing process, populations of microorganisms generally lose their viability in an exponential fashion, independent of the initial number of organisms . This can be represented graphically with a ‘survivor curve ’ drawn from a plot of the logarithm of the fraction of survivors against the exposure time or dose. Survivor curves

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3/21/2012 Surviving fraction Typical survivor curves for bacterial spores exposed to moist heat or gamma-radiation

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3/21/2012 Expression of resistance D-value D-value is indicative of the resistance of any organism to a sterilizing agent. For radiation and heat treatment , D-value is the time taken at a fixed temperature or the radiation dose required to achieve a 90% reduction in viable count.

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3/21/2012 Z-value Z-value represents the increase in temperature needed to reduce the D-value of an organism by 90%.

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3/21/2012 The various methods of sterilization are: 1. Physical Method a. Thermal (Heat) methods b. Radiation method c. Filtration method 2. Chemical Method a. Gaseous method Methods of Sterilization

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3/21/2012 Heat Sterilization Heat sterilization is the most widely used and reliable method of sterilization , involving destruction of enzymes and other essential cell constituents . The process is more effective in hydrated state where under conditions of high humidity, hydrolysis and denaturation occur , thus lower heat input is required. Under dry state, oxidative changes take place in process. This method of sterilization can be applied only to the thermostable products.

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3/21/2012 principle : Dry-heat sterilization is accomplished by thermal (heat) conduction . Initially, heat is absorbed by the exterior surface of an item and then passed to the next layer . Eventually, the entire object reaches the temperature needed for sterilization. Death of microorganisms occurs with dry heat by a process of slow destruction of protein . Dry-heat sterilization takes longer than steam sterilization , because the moisture in the steam sterilization process significantly speeds up the penetration of heat and shortens the time needed to kill microorganisms . RED HEAT , FLAMING , HOT AIR OVEN Dry Heat Sterilization

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3/21/2012 1. Fan motor 2. Sirocco fan 3. Exterior 4. Insulating material 5. Interior 6. Holes Plate 7. Shelf 8. Hot air circulation 9. Fresh air inlet 10. Exhaust 11. Heater

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3/21/2012 STEP 1: Decontaminate, clean and dry all instruments and other items to be sterilized. STEP 2: If desired, wrap instruments in aluminum foil or place in a metal container with a tight-fitting, closed lid . Wrapping helps prevent recontamination prior to use. Hypodermic or suture needles should be placed in glass tubes with cotton stoppers . STEP 3: Place loose ( unwrapped ) instruments in metal containers or on trays in the oven and heat to desired temperature. STEP 4: After the desired temperature is reached , begin timing . procedure

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3/21/2012 STEP 5: After cooling, remove packs and/or metal containers and store . Loose items should be removed with sterile forceps/pickups and used immediately or placed in a sterile container with a tight-fitting lid . The following temperature/time ratios are recommened: 170⁰C 60 min 160 ⁰C 120 min 150 ⁰C 150 min 140 ⁰C 180 min 121 ⁰C overnight

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3/21/2012 Dry heat: 170⁰C for 1 hour (total cycle time—placing instruments in oven, heating to 170⁰C, timing for 1 hour, and then cooling—is from 2–2.5 hours ), Or 160⁰C for 2 hours (total cycle time is from 3–3.5 hours ). note : Exposure time begins only after the sterilizer has reached the target temperature. Do not overload the sterilizer. (Leave at least 7.5 cm [3 inches] between the items and walls of sterilizer .) Overloading alters heat convection and increases the time required to sterilize. Standard Conditions for dry Heat Sterilization

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3/21/2012 Advantages Effective method , as dry heat by conduction reaches all surfaces of instruments , even for instruments that cannot be disassembled . Protective of sharps or instruments with a cutting edge (fewer problems with dulling of cutting edges). Leaves no chemical residue . Eliminates “wet pack” problems in humid climates. Disadvantages Plastic and rubber items cannot be dry-heat sterilized because temperatures used (160–170⁰C ) are too high for these materials. Dry heat penetrates materials slowly and unevenly . Requires oven and continuous source of electricity

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3/21/2012 Principles : Steam is an effective sterilant for two reasons. First, saturated steam is an extremely effective “carrier” of thermal energy. It is many times more effective in conveying this type of energy to the item than is hot (dry) air. Second, steam is an effective sterilant because any resistant, protective outer layer of the microorganisms can be softened by the steam , allowing coagulation (similar to cooking an egg white) of the sensitive inner portions of the microorganism. STERILIZATION BY STEAM

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3/21/2012 STEP 1 : Decontaminate, clean and dry all instruments and other items to be sterilized . STEP 2: All jointed instruments should be in the opened or unlocked position , while instruments composed of more than one part or sliding parts should be disassembled . Note: To help prevent dulling of sharp points and cutting edges, wrap the sharp edges and needle points in gauze before sterilizing . Repair (sharpen) or replace instruments as needed. Note: Do not allow to boil dry . Steam should always be escaping from the pressure valve. procedure

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3/21/2012 STEP 3 : Instruments should not be held tightly together by rubber bands or any other means that will prevent steam contact with all surfaces. STEP 4: Arrange packs in the chamber to allow free circulation and penetration of steam to all surfaces . STEP 5: When using a steam sterilizer, it is best to wrap clean instruments or other clean items in a double thickness of muslin or newsprint . ( Unwrapped instruments must be used immediately after removal from the sterilizer, unless kept in a covered, sterile container.) STEP 6 : Sterilize at 121⁰C for 30 minutes for wrap ped items, 20 minutes for unwrapped items ; time with a clock.

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3/21/2012 STEP 7: Wait 20 to 30 minutes (or until the pressure gauge reads zero) to permit the sterilizer to cool sufficiently. Then open the lid or door to allow steam to escape . Allow instrument packs to dry completely before removal, which may take up to 30 minutes . STEP 8: To prevent condensation , when removing the packs from the chamber, place sterile trays and packs on a surface padded with paper or fabric . STEP 9: After sterilizing, items wrapped in cloth or paper are considered sterile as long as the pack remains clean , dry (including no water stains) and intact. Unwrapped items must be used immediately or stored in covered, sterile containers.

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3/21/2012 Steam sterilization: Temperature should be 121⁰C ;pressure should be (15 lbs/in ² ); 20 minutes for unwrapped items ; 30 minutes for wrapped items . Or at a higher temperature of 132⁰C,pressure should be 30 lbs/in ² ; 15 minutes for wrapped items. Allow all items to dry before removing them from the sterilizer. Note: Pressure settings ( kPa or lbs/in2) may vary slightly depending on the sterilizer used. When possible, follow manufacturers’ recommendations . Standard Conditions for steam Heat Sterilization

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3/21/2012 Advantages Most commonly used, effective method of sterilization. Sterilization cycle time is shorter than with dry heat or chemical sterilants. Disadvantages Requires a continuous source of heat ( wood fuel, kerosene or electricity). Requires equipment (steam sterilizer), which must be expertly maintained to keep it in working condition . Requires strict adherence to time, temperature and pressure settings. Difficult to produce dry packs because breaks in procedure are common (e.g., not allowing items to dry before removing, especially in hot, humid climates ). Repeated sterilization cycles can cause pitting and dulling of cutting edges of instruments (i.e., scissors). Plastic items cannot withstand high temperatures. Non stainless steel metal items corrode

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3/21/2012 Radiation Sterilization Many types of radiation are used for sterilization like electromagnetic radiation (e.g. gamma rays and UV light), particulate radiation (e.g. accelerated electrons) . The major target for these radiation is microbial DNA. Gamma rays and electrons cause ionization and free radical production while UV light causes excitation . Radiation sterilization is generally applied to articles in the dry state; including surgical instruments, sutures , unit dose ointments, plastic syringes and dry pharmaceutical products. UV light, with its much lower energy, and poor penetrability finds uses in the sterilization of air, for surface sterilization of aseptic work areas, for treatment of manufacturing grade water, but is not suitable for sterilization of pharmaceutical dosage forms.

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3/21/2012 Gamma ray Sterilizer: Gamma rays for sterilization are usually derived from cobalt-60 source , the isotope is held as pellets packed in metal rods , each rod carefully arranged within the source and containing 20 KCi of activity . This source is housed within a reinforced concrete building with 2 m thick wall s. Articles being sterilized are passed through the irradiation chamber on a conveyor belt and move around the raised source. Electron Accelerator There are two types of electron accelerator machines, the electrostatic accelerator which produces electrons with maximum energies of 5 MeV , and the microwave linear accelerator which produces electrons with maximum energies of 10 MeV . Higher energies cause better penetration into the product but there is a risk of induced radiation.

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3/21/2012 Ultraviolet Irradiation: The optimum wavelength for UV sterilization is 260 nm . A mercury lamp giving peak emission at 254 nm is the suitable source of UV light in this region. Disadvantages of UV : UV irradiation can interrupt transmission of airborne infections in enclosed indoor environments where living conditions are poor and people are crowded together. Because UV irradiation has very limited energy, UV light does not penetrate dust, mucous or water. UV rays can kill only those microorganisms that are struck directly by UV light beams. For surfaces that cannot be reached by the UV rays (e.g., inside the barrel of a needle or laparoscope ),

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3/21/2012 It requires a reliable source of electricity. It is not effective in areas of high relative humidity . UV bulbs require frequent cleaning to remain effective . Exposure to UV rays can burn the skin and eyes not effective method in most situation

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3/21/2012 Filtration process does not destroy but removes the microorganisms . It is used for both the clarification and sterilization of liquids and gases as it is capable of preventing the passage of both viable and non viable particles. The major mechanisms of filtration are sieving, adsorption and trapping within the matrix of the filter material. Sterilizing grade filters are used in the treatment of heat sensitive inject ions and ophthalmic solutions, biological products and air and other gases for supply to aseptic areas . They are also used in industry as part of the venting systems on fermentors , centrifuges, autoclaves and freeze driers . Membrane filters are used for sterility testing. Filtration Sterilization

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3/21/2012 Application of filtration for sterilization of gases: HEPA (High efficiency particulate air) filters can remove up to 99.97% of particles >0.3 micrometer in dia meter. Air is first passed through prefilters to remove larger particles and then passed through HEPA filters. The performance of HEPA filter is monitored by pressure differential and airflow rate measurements.

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3/21/2012 An alternative to high-pressure steam or dry-heat sterilization is chemical sterilization (often called “cold sterilization”). If objects need to be sterilized, but using high-pressure steam or dry-heat sterilization would damage them Some high-level disinfectants will kill endospores after prolonged ( 10–24 hour) exposure . Common disinfectants that can be used for chemical sterilization include glutaraldehydes and formaldehyde CHEMICAL STERILIZATION

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3/21/2012 Glutaraldehydes Sterilization takes place by soaking for at least 10 hours in 2–4% glutaraldehyde solution Glutaraldehydes, such as Cidex , are often in short supply and very expensive Formaldehyde Sterilization takes place by soaking for at least 24 hours in 8% formaldehyde solution. formaldehyde is less expensive than glutaraldehydes

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3/21/2012 (ETO) gas is used for sterilization of heat- and moisture-sensitive surgical instruments, such as plastic devices and delicate instruments. Sterilization using ETO, however, is a more complicated (requires a 2-hour exposure time and a long aeration period ) expensive process than either steam or dry-heat sterilization. Ethylene Oxide

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3/21/2012 STEP 1: Decontaminate, clean and dry all instruments and other items to be sterilized. STEP 2: Completely submerge items in a clean container filled with the chemical solution and place the lid on the container. STEP 3: Allow items to soak: 10 hou rs in a glutaraldehyde (check specific product instructions), or at least 24 hours in 8% formaldehyde STEP 4: Remove objects from the solution with sterile forceps ; rinse all STEP 5: Store objects in a sterile container with a tight-fitting li d if they will not be used immediately. procedure

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3/21/2012 Advantages Glutaraldehydes and formaldehyde solutions are not readily inactivated by organic materials. Both can be used for items that will not tolerate heat sterilization such as laparoscopes. Formaldehyde solutions can be used for up to 14 days (replace sooner if cloudy ); some glutaraldehydes can be used for up to 28 days.

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3/21/2012 Disadvantages Glutaraldehydes and formaldehyde are chemicals that cause skin irritation ; therefore, all equipment soaked in either solution must be thoroughly rinsed with sterile water after soaking . Because glutaraldehydes work best at room temperature , chemical sterilization cannot be assured in cold environments (temperatures less than 20°C) , even with prolonged soaking . Glutaraldehydes are expensive. Vapors from formaldehyde (classified as a potential carcinogen ), and to a lesser degree of irritation to the skin, eyes and respiratory tract . Wear gloves and eyewear, limit exposure time and use both chemicals only in well-ventilated areas . Formaldehyde cannot be mixed with chlorine or chlorinated water because a dangerous gas ( bis - chloromethyl -ether ) is produced.

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3/21/2012 ETO is hazardous to healthcare workers , patients , ETO is moderately toxic when inhaled , regular exposure to low levels (greater than 1 part per million ) may produce harmful effects in humans. Residual ETO on Instruments Can Cause Skin Injuries And Inflammatory Reactions In Patients Ethylene oxide, a toxic product, is classified as a potential carcinogen as well as a mutagen.

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3/21/2012 Paracetic acid ( peroxyacetic acid). The acid is rapidly effective against all microorganisms , organic matter does not diminish its activity and it decomposes into safe products . When diluted , it is very unstable and must be used with a specially designed automatic sterilizer. Paraformaldehyde . This solid polymer of formaldehyde may be vaporized by dry heat in an enclosed area to sterilize objects . This technique, called “self-sterilization ”, may be well suited for sterilizing endoscopes and other heat-sensitive instruments. Gas plasma sterilization (hydrogen peroxide based). This method can sterilize items in less than 1 hour and has no harmful by products. It does not penetrate well , however, and cannot be used on paper or linen .

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3/21/2012 Thank you

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