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Barrier Methods And Cross Infection Control

Published in: MBBS Tuition
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This presentation explains in detail and illustrative manner about the importance of sterilization in a clinical setting and the methods of infection control. It is imperative for every individual to be aware of all these aspects of health care.

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    INTRODUCTION In spite of scientific advances in understanding the pathogenesis of various diseases and better understanding of pharmacotherapy, infection remains one of the most important concerns of medical and dental practitioners. Therefore, every attempt should be made to minimise the infection rate. Proper sterilization, along with other methods ensure control of cross-infection in a dental office. Cross-infection control is imperative for not only the patients themselves, but also for the clinicians, staff and attendants.
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    BASIC DEFINITIONS (Medical Microbiology, Greenwood) INFECTION: The invasion and multiplication of microorganisms such as bacteria, viruses, and parasites that are not normally present within the body. STERILIZATON: It is a process used to achieve sterility, an absolute term meaning the absence of all viable microorganisms. DISINFECTION: It is a process which reduces the number of contaminating micro-organisms, particularly those liable to cause infection, to a level which is deemed no longer harmful to health. ANTISEPSIS: Disinfection applied to living tissue, such as a wound. CLEANING: Soil-removing process which removes many micro-organisms. DECONTAMINATION: General term for the treatment used to make equipment safe to handle, and includes microbiological, chemical, radioactive and other contamination.
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    STERILIZATION: Freeing of an article from all living organisms, including viruses, bacteria and their spores, and fungi and their spores. All instruments should be thoroughly cleaned before sterilization. Methods of sterilization include: 1) Physical Agents 2) Chemical Agents
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    PHYSICAL AGENTS: 1. 2. 3. a) b) 4. 5. 6. Sunlight Drying Heat: Dry heat — Red heat, Flaming, Incineration, Hot air oven Moist heat — Pasteurization, Boiling, Steam under pressure Filtration Radiation Sonic and ultrasonic vibrations
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    CHEMICAL AGENTS: 1. 2. 3. 4. 5. 6. 7. 8. Alcohols Aldehydes Dyes Halogens Phenols Surface active agents Metallic salts Gases
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    PHYSICAL AGENTS: l. SUNLIGHT The microbicidal activity of sunlight is mainly due to the presence of ultra violet rays. It is responsible for spontaneous sterilization in natural conditions.
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    2. DRYING Complete removal of the moisture content Unreliable because the spores are not killed.
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    3. i. a). DRY HEAT Red Heat Articles such as bacteriological loops, straight wires, tips of forceps and searing spatulas are sterilized by holding them in Bunsen flame till they become red hot. This is a simple method for effective sterilization of such articles, but is limited to those articles that can be heated to redness in flame.
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    ii. Flaming This is a method of passing the article over a Bunsen flame, but not heating it to redness. Articles such as scalpels, mouth of test tubes, flasks, glass slides and cover slips are passed through the flame a few times.
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    Incineration This is a method of destroying contaminated material by burning them in incinerator, and reducing them to ashes. Articles such as soiled dressings; animal carcasses, pathological material and bedding etc should be subjected to incineration.
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    iv. Hot air oven Introduced by Louis Pasteur. Articles to be sterilized are exposed to high temperature (1 60 degree C) for duration of one hour in an electrically heated oven.
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    Articles sterilized: - Metallic instruments (like forceps, scalpels, scissors) - Glassware (such as petri-dishes, pipettes, flasks) - Swabs - Pharmaceutical products. Sterilization cycle: - 60 minutes at 160 degree C - 40 minutes at 170 degree C - 20 minutes at 180 degree C
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    3. i. b). MOIST HEAT AT TEMPERATURE BELOW IOO DEGREE CELSIUS: PASTEURIZATION: There are two methods of pasteurization: - Holder method (heated at 63 degree C for 30 minutes) - Flash method (heated at 72 degree C for 15 seconds), followed by quickly cooling to 13 degree C. VACCINE BATH SERUM BATH INSPISSATION
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    AT IOO DEGREE CELSIUS: BOILING TYNDALLISATION STEAM AT IOO DEGREE - Koch's steam sterilizer - Arnold's steam sterilizer
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    iii. AT TEMPERATURE ABOVE IOO DEGREE CELSIUS: AUTOCLAVE Water boils at 1 00 degree C at atmospheric pressure, but if pressure is raised, the temperature at which the water boils also increases. In an autoclave the water is boiled in a closed chamber. As the pressure rises, the boiling point of water also raises. At a pressure of 15 lbs inside the autoclave, the temperature is said to be 121 degree C. Exposure of articles to this temperature for 15 minutes sterilizes them. 7
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    Exhaust valve (to remove steam after sterilization) Steam to chamber Safety valve Pressure gauge Steam Operating valve (controls steam from jacket to chamber) Steam chamber Air Door Sediment screen Thermometer Perforated shelf Steam jacket Automatic ejector valve is thermostatically controlled and closes on contact with pure steam when air is exhausted. To waste line Copyright C 2004 Pearcon Education, bc.. pWishing as Benarnin Cummings. Pressure regulator for steam supply Steam supply
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    4. FILTRATION Filtration does not kill microbes, it separates them out. Membrane filters with pore sizes between 0.2-0.45 um are commonly used to remove particles from solutions that can't be autoclaved. It is used to remove microbes from heat labile liquids such as serum, antibiotic solutions, sugar solutions, urea solution. particle filter media fluid feed filtrate
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    , TYPES OF FILTERS: 1. 2. 3. 4. Earthenware filters a) Pasteur-Chamberland Filter b) Berkfeld filter c) Mandler filter Asbestos filters Sintered glass filters Membrane filters
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    5. RADIATION Two types of radiation are used, non-ionizing and ionizing. Non-ionizing (such as Infrared rays and ultraviolet rays) rays are low energy rays with poor penetrative power. Ionizing rays (such as gamma rays, X-rays, cosmic rays) are high-energy rays with good penetrative power. Since radiation does not generate heat, it is termed "cold sterilization".
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    6. SONIC AND ULTRSONIC VIBRATIONS Sound waves of frequency cycle/second kills bacteria and some viruses on exposing for one hour. High frequency sound waves disrupt cells. They are used to clean and disinfect instruments as well as to reduce microbial load. This method is not reliable since many viruses and phages are not affected by these waves.
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    CHEMICAL AGENTS: l. ALCOHOLS Mode of action: Alcohols dehydrate cells, disrupt membranes and cause coagulation of protein. Examples: Ethyl alcohol, isopropyl alcohol and methyl alcohol Application: A 70% aqueous solution is more effective at killing microbes than absolute alcohols. 70% ethyl alcohol (spirit) is used as antiseptic on skin. Isopropyl alcohol is preferred to ethanol. It can also be used to disinfect surfaces. It is used to disinfect clinical thermometers. Methyl alcohol kills fungal spores, hence is useful in disinfecting inoculation hoods. Disadvantaqes: Skin irritant, volatile (evaporates rapidly), inflammable
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    2. ALDEHYDES Mode of action: Acts through alkylation of amino-, carboxyl- or hydroxyl group, and probably damages nucleic acids. It kills all microorganisms, including spores. Examples: Formaldehyde, Gluteraldehyde Application: 40% Formaldehyde (formalin) is used for surface disinfection and fumigation of rooms, chambers operation theatres, biological safety cabinets, wards, sick rooms etc. -2% gluteraldehyde is used to sterilize thermometers, cystoscopes, bronchoscopes, centrifuges, anasethetic equipments etc. Disadvantages: Vapors are irritating (must be neutralized by ammonia), has poor penetration, leaves non-volatile residue, activity is reduced in the presence of protein. -Gluteraldehyde requires alkaline pH and only those articles that are wettable can be sterilized.
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    3. DYES Mode of action: Acridine dyes are bactericidal because of their interaction with bacterial nucleic acids. Examples: Aniline dyes such as crystal violet, malachite green and brilliant green. Acridine dyes such as acriflavin and aminacrine. Applications: They may be used topically as antiseptics to treat mild burns. They are used as paint on the skin to treat bacterial skin infections. The dyes are used as selective agents in certain selective media.
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    4. HALOGENS Mode of action: They are oxidizing agents and cause damage by oxidation of essential sulfydryl groups of enzymes. Examples: Chlorine compounds (chlorine, bleach, hypochlorite) and iodine compounds (tincture iodine, iodophores). Applications: Tincture of iodine (2% iodine in 70% alcohol) is an antiseptic. For hand washing iodophores are diluted in 50% alcohol. - 10% Povidone Iodine is used undiluted in pre and postoperative skin disinfection. Disadvantaqes: They are rapidly inactivated in the presence of organic matter. - Iodine is corrosive and staining.- - Bleach solution is corrosive and will corrode stainless steel surfaces.
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    5. PHENOLS Mode of action: Act by disruption of membranes, precipitation of proteins and inactivation of enzymes. Examples: 5% phenol, 1-5% Cresol, 5% Lysol (a saponified cresol), hexachlorophene, chlorhexidine, chloroxylenol (Dettol). Applications: Chlorhexidine can be used in an isopropanol solution for skin disinfection, or as an aqueous solution for wound irrigation. It is often used as an antiseptic hand wash. - 20% Chlorhexidine gluconate solution is used for pre-operative hand and skin preparation and for general skin disinfection. Disadvantages: It is toxic, corrosive and skin irritant. - Chlorhexidine is inactivated by anionic soaps. - Chloroxylenol is inactivated by hard water.
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    6. SURFACE ACTIVE AGENTS Mode of action: They have the property of concentrating at interfaces between lipid containing membrane of bacterial cell and surrounding aqueous medium. They disrupt membrane resulting in leakage of cell constituents. Examples: These are soaps or detergents. Detergents can be anionic or cationic. - Anionic detergents include soaps and bile salts. - Cetrimide and benzalkonium chloride act as cationic detergents. Application: They are widely used as disinfectants at dilution of 1-2% for domestic use and in hospitals. Disadvantages: Their activity is reduced by hard water, anionic detergents and organic matter.
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    7. METALLIC SALTS Mode of action: Act by precipitation of proteins and oxidation of sulfydryl groups. They are bacteriostatic. Examples: Mercuric chloride, silver nitrate, copper sulfate, organic mercury salts (e.g., mercurochrome, merthiolate) Applications: Mercurials are active against viruses at dilution of 1 :500 to 1 : 1000. Merthiolate at a concentration of 1 :1 0000 is used in preservation of serum. Copper salts are used as a fungicide. Disadvantaqes: Mercuric chloride is highly toxic, are readily inactivated by organic matter.
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    8. i. ii. iii. GASES Formldehyde gas Ethylene oxide Beta-propiolactone
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    TESTING OF DISINFECTANTS A disinfectant must be tested to know the required effective dilution, the time taken to effect disinfection and to periodically monitor its activity. As disinfectants are known to lose their activity on standing as well as in the presence of organic matter, their activity must be periodically tested. Different methods: 1. Koch's method 2. Rideal Walker Method 3. Chick Martin test 4. Capacity use dilution test (Kelsey-Sykes test) 5. In-use test
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    BARRIER METHODS USED IN DAILY CLINICAL PRACTICE 1. 2. 3. 4. 5. 6. 7. Gloves Gowns Mouth masks Head caps Face shields Protective eye wear Patients' drapes
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    l. GLOVES Examination and treatment wherein contact with skin, mucosa or body fluids is encountered . Gloves should be changed between patients or when they are torn or punctured.
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    2. GOWNS Gowns, aprons, or lab coats are required when splashes on the skin or clothing with body fluids are likely to occur. Protect all areas of exposed skin of the operator and the patient.
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    3. MOUTH MASKS Simple surgical masks protect wearers from being splashed in the mouth with body fluids and to prevent transmission of body fluids from the medical professional to the patient. They can also reduce the spread of infectious liquid droplets (carrying bacteria or viruses) that are created when the wearer coughs or sneezes. Surgical masks become soaked with moisture after about 2 to 3 hours, which causes them to lose their efficacy.
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    4. HEAD CAPS Hair should be properly and neatly tied. To avoid hair contamination, hair cover/caps must be used.
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    5. FACE SHIELDS A face shield is a device used to protect wearer's entire face. Used when splattering of fluids is expected.
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    6. PROTECTIVE EYEWEAR To prevent trauma to the eye tissue from flying droplets or aerosols containing infectious microbe debris.
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    7. PATIENT DRAPE Isolate the field of surgery from other parts of the body, that have not prepared for surgery and also from non sterile equipments.
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    HANDWASHING Hand hygiene is regarded as one of the most important element of infection control activities. If properly implemented, hand hygiene alone can significantly reduce the risk of cross-transmission of infection in healthcare facilities.
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    STEPS OF HANDWASHING (a) Wet hands under running water (e) Grip the fingers on each hand (b) Apply soap and rub palms together to ensure complete coverage (f) Pay particular attention to the thumbs (c) Spread the lather over the backs of the hands (g) Press fingertips into the palm of each hand (d) Make sure the soap gets in between the fingers (h) Dry thoroughly with a clean towel
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    CONCLUSION We must remember that there is a standard of care that everyone has a right to expect from their dental treatment. Proper sterilisation, cleanliness and the use of barrier methods should be at the top of the agenda in a dental set-up. Infection control is the discipline concerned with preventing nosocomial or healthcare-associated infection.
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    ΤΙ-ΙΑΝΚ γου


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