Sterilization and Infection Control PDF

Sterilization and Infection control Terminology • Sterilization :process by which as article, surface and medium is freed of microorganisms either in vegetable or sport state. • Disinfection: Means destruction of all pathogenic microorganisms, or organisms capable of giving rise to infection. Spo...

Sterilization and Infection control Terminology • Sterilization :process by which as article, surface and medium is freed of microorganisms either in vegetable or sport state. • Disinfection: Means destruction of all pathogenic microorganisms, or organisms capable of giving rise to infection. Spore forms may survive even after disinfection. • Decontamination: is the reduction of the number of viable microorganisms • Disinfectant: A chemical used on nonvital object to kill surface vegetative pathogenic microorganisms, but not necessarily sport forms or viruses. • Antiseptic: A chemical that is applied to living tissue such as skin or mucous membrane to reduce the no. of microorganisims present through inhibition of their activity or destruction. • Sepsis is the breakdown of living tissue by the action of microorganisms and is usually accompanied by inflammation. • Medical asepsis is the attempt to keep patients, health care staff, and objects as free as possible of agents that cause infection. • Surgical asepsis is the attempt to prevent microbes from gaining access to surgically created wounds. Sterilization with Heat • Moist heat is probably more effective because dry heat oxidizes cell proteins, a process requiring extremely high temperatures, whereas moist heat causes destructive protein coagulation quickly at relatively low temperatures. • The spore of the bacterium Bacillus stearothermophilus is extremely resistant to heat and is, therefore, used to test the reliability of heat sterilization. • It has been shown that 6 months after sterilization, the possibility of organisms entering sterilization bags increases, although some individuals think that an even longer period is acceptable Dry heat This method should be used only for materials that might be damaged by moist heat or that are impenetrable to moist heat (e.g., powders, petroleum products, sharp instruments. • Advantages: a) Nontoxic and does not harm the environment b) Dry heat cabinet is easy to install and has relatively low operating costs; c) It is noncorrosive for metal and sharp instruments Disadvantages: 1- High temperatures may damage more heat-sensitive items, such as rubber or plastic goods. 2- Sterilization cycles are prolonged at the lower temperatures. 3- Heavy loads of instruments, crowding of packs, and heavy wrapping easily defeat sterilization. 4-Hot air is bad conductor of heat hence it has less penetrating power. Glass bead sterilizer • Glass beads (1.2-1.5 mm diameter) • High tempretaure (217-232 C) • Brief exposure (10-45 seconds) • Small instruments (reamers, files, burs) • The sterilizer is turned on till it reaches the desired temperature (may takes 10 minutes), then the instruments are submerged into these beads and kept there for about 10-45 seconds Moist heat (steam under pressure-autoclave) • water is better than air at transferring heat. • The increasing pressure in a container of steam increases the boiling point of water so that the new steam entering a closed container gradually becomes hotter. • When steam comes into contact with an object, the steam condenses and almost instantly releases that stored heat energy, which quickly denatures vital cell proteins. Parameters for steam sterilizers 1. Steam: steam for sterilization is dry saturated steam 2. Pressure: pressure serves as a mean to obtain the high temperature necessary to quickly kill micoorganisms 3. Temperature: Specific temperatures must be obtained to ensure the micobicidal activity. The two most common steam-sterilizing temperatures are 121 C and 134 C. 4. Time: The recommended temperatures must be maintained for a minimal time to kill microorganisms • 121 C for 15-20 minutes at 15 psi pressure • 134 C for 4 minutes at 32 psi pressure Types of steam sterilizers • the gravity displacement autoclave: steam is admitted at the top or the sides of the sterilizing chamber and, because the steam is lighter than air, forces air out the bottom of the chamber through the drain vent. The gravity displacement autoclaves are primarily used to process laboratory media, water, pharmaceutical products, regulated medical waste, and nonporous articles whose surfaces have direct steam contact. For gravity displacement sterilizers the penetration time into porous items is prolonged because of incomplete air elimination. • high-speed prevacuum sterilizer: fitted with a vacuum pump (or ejector) to ensure air removal from the sterilizing chamber and load before the steam is admitted. The advantage of using a vacuum pump is that there is nearly instantaneous steam penetration even into porous loads. Advantages of autoclave 1. The most effective form of destruction of all forms of microbial life. 2. Temperature can be accurately controlled. 3. Heating and penetration of heat is rapid. 4. Short sterilization time. Disadvantages of autoclave 1. Corrosion of delicate instruments. 2. Unsuitable for sterilization of oils or powers 3. Rubber or plastic goods may be damaged 4. Autoclave should be loaded properly ,otherwise, it may not be effective. Sterilization monitoring Biological indicator: Spores of Geobacillus stearothermophilus (formerly called Bacillus stearothermophilus) are the best indicator because they are resistant to steam. Their spores are killed in 12 minutes at 121°C Autoclave tapes: Adhesive-backed paper tape with heat-sensitive, chemical indicator marking that changes color or display-diagonal stripes, the words “sterile” or “autoclaved” when exposed to effective sterilization temperature (121°C) are used to check the efficacy of autoclaves. Browne’s tube (invented by Albert Browne in 1930) contains a heat-sensitive red dye that turns green after being exposed to a certain temperature for a definite period of time Stages for instrument sterilization ►Presoaking - Placing the instrument in a presoak solution until time is available forfull cleaning prevents drying and begins to dissolve or soften the debris. Presoak solutions used are detergents ►Cleaning - Clean instruments in an ultrasonic cleaner (preferred), instrument washer, or by hand while wearing proper protection. Ultrasonic cleaners are safest and most efficient ways to clean instruments, ultrasonic cleaning is 9 times more effective than hand cleaning ,it provides fast and thorough cleaning without damage to instruments. ►Packaging - Place instruments in a sealed package or pouch, unless you're going to use them immediately after sterilization. ►Sterilization- Sterilize instruments using steam autoclaving, dry-heat, or chemical vapor machines. ►Drying or cooling- Store Instruments in a Dry, Protected Area Sterilization with Gas • • • • ethylene oxide is the most commonly used. Ethylene oxide is a highly flammable gas, so it is mixed with carbon dioxide or nitrogen At 50°C ethylene oxide is effective for killing all organisms, including spores, within 3 hours. because it is highly toxic to animal tissue, equipment exposed to ethylene oxide must be aerated for 8 to 12 hours at 50°C to 60°C, or at ambient temperatures for 4 to 7 days. • The advantages of ethylene oxide for sterilization are its effectiveness for sterilizing porous materials, large equipment, and materials sensitive to heat or moisture. • The disadvantages are the need for special equipment, and the length of sterilization and aeration time necessary to reduce tissue toxicity. This technique is rarely practical for dental use Instrument Disinfection • Substances acceptable for disinfecting dental instruments for surgery include glutaraldehyde, iodophors, chlorine compounds, and formaldehyde; glutaraldehyde-containing compounds are the most commonly used. • Alcohols are not suitable for general dental disinfection because they evaporate too rapidly; however, they can be used to disinfect local anesthetic cartridges. • Quaternary ammonium compounds are not recommended for dentistry because they are not effective against the hepatitis B virus and become inactivated by soap. To ensure maximal disinfection • The agent must be properly reformulated and discarded periodically, as specified by the manufacturer. • Instruments must remain in contact with the solution for the designated period. • All instruments must be washed free of blood or other visible material before being placed in the solution. • After disinfection the instruments must be rinsed free of chemicals and used within a short time Operatory Disinfection • Any surface that a patient or patient’s secretions contact is a potential carrier of infectious organisms. • when high-speed drilling equipment is used, patient blood and secretions are dispersed over much of the surfaces of the operatory. • The operatory can be disinfected in two basic ways. The first is to wipe all surfaces with a hospital-grade disinfectant solution. The second is to cover surfaces with protective shields that are changed between each patient. • chlorine compounds and glutaraldehyde, can prevent transfer of the hepatitis viruses when used on surfaces in certain concentrations (0.2% for chlorine, 2% for glutaraldehyde) Infection control program in minimum dental office 1.Sterilization of instruments 2.Comprehensive medical history 3.Hepatitis B vaccine to prevent any cross infection 4.Antiseptic and mouthwash 5.Disposal mask and gloves 6.Protective eye glass 7.Rubber dam 8.Surface cleaning and cover tray 9.Needle and sharp instrument safety Sharps management • The most common risk for transmission of disease from infected patients to the staff is by accidental needle sticks or scalpel lacerations. • Sharps injuries can be prevented by using the local anesthetic needle to scoop up the sheath after use, using an instrument such as a hemostat to hold the cover while resheathing the needle, or using automatically resheathing needles • never to apply or remove a blade from a scalpel handle without an instrument; and disposing of used blades, needles, and other sharp disposable items into rigid, well-marked receptacles specially designed for contaminated sharp objects Risk of viral hepatitis transmission • Hepatitis B virus has the most serious risk of transmission for unvaccinated dentists, their staff members, and their patients. • This virus is usually transmitted by the introduction of infected blood into the bloodstream of a susceptible person; • . Minute quantities of the virus have been found capable of transmitting disease (only 105 to 107 virions/mL blood) • Unlike most viruses, hepatitis B virus is exceptionally resistant to desiccation and chemical disinfectants, including alcohols, phenols, and quaternary ammonium compounds. • Fortunately, means of inactivating the hepatitis B virus include halogen-containing disinfectants (e.g., iodophor and hypochlorite), formaldehyde, ethylene oxide gas, all types of properly performed heat sterilization, and irradiation. Risk of HIV infection • HIV acts in a fashion similar to other agents of sexually transmitted diseases (STDs). That is, transfer of the virions from one individual to another requires direct contact between virus-laden blood or secretions from the infected host organism and a mucosal surface or epithelial wound. • Evidence has shown that the HIV loses its infectivity once dessicated. • few persons carrying HIV secrete the virus in their saliva, and those who do tend to secrete extremely small amounts. No epidemiologic evidence supports the possibility of HIV infection via saliva alone. • Even the blood of patients who are HIV-positive has low concentrations of infectious particles (106 particles/mL compared with 1013 particles/mL in hepatitis patients). This probably explains why professionals have an extremely low probability of contracting it, even when exposed to the blood and secretions of large numbers of patients who are HIV positive. Risk of transmission of Mycobacterial organisms • Mycobacterium tuberculosis. • TB is transmitted primarily through exhaled aerosols that carry M. tuberculosis bacilli from the infected lungs. • Droplets are produced by those with untreated TB during breathing, coughing, sneezing, and speaking. • M. tuberculosis is not a highly contagious microorganism. • transmission can also occur via inadequately sterilized instruments because although M. tuberculosis organisms do not form spores, they are highly resistant to desiccation and to most chemical disinfectants. • The organisms are sensitive to heat, ethylene oxide, and irradiation. • To prevent transmission of TB from an infected individual to the dental staff, the staff should wear face-masks (specifically, surgical N95 respirator masks). • all reusable instruments and supplies should be sterilized with heat or ethylene oxide gas. • patients with untreated TB should have their surgery postponed