Chapter 7 – Microbiology Test Questions – Flashcards
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Noscominal Infection |
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A disorder acquired during an individual’s stay at a hospital or chronic care facility |
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Sterilization |
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the removal of all life forms, including bacterial species -includes spores and viruses |
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Microbicidal |
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referring to any agent that kills microbes |
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Bactericidal |
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referring to any agent that kills bacterial cells |
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Fungicidal |
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referring to any agent that kills fungi |
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Contaminated |
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in microbiology, a once sterile object that is again harboring microorganisms and/or viruses |
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Sanitization |
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to remove microbes or reduce their populations to a safe level as determined by public health standards |
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Microbiostatic |
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referring to any agent that inhibits growth of microbes |
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Bacteriostatic |
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referring to any substance that prevents the growth of bacteria |
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Fungistatic |
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referring to any substance that inhibits the growth of fungi |
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Heat |
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fast, reliable, and relatively inexpensive. Above the growth range temperature for a microbe, enzymes and other proteins as well as nucleic acids are denatured. It also drives off water, and since all organisms depends on water it can be fatal |
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Killing Rate of Heat |
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expressed as a function of time and temperature i.e. bacilli of Mycobacterium tuberculosis 30 mins at 58oC, 2 mins at 65oC, and few seconds at 72oC |
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Thermal Death TIme (TDT) |
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the length of time required to kill a bacterial population at a give temperature |
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Thermal Death Point (TDP) |
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the temperature required to kill a bacterial population at a given temperature |
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Incineration |
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Using a direct flame can destroy microbes very rapidly i.e. flame of the Bunsen burner is employed for a few seconds to sterilize the bacteriological loop before removing a sample from a culture tube > disposable hospital gowns and certain plastic apparatus can use this method |
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Foot Mouth Disease |
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A highly contagious viral disease affecting cattle, sheep, and pigs, in which the animal develops ulcers, in the food and near the hooves |
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Dry Heat |
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uses radiating dry heat for sterilization, the type of energy does not penetrate materials easily, therefore it requires long periods of exposure to high temperatures i.e. at a temperature of 160OC (320OF) a period of two hours is required for the destruction of bacterial spores > recommended for sterilizing dry powders and water-free oily substances, many types of glassware (pipettes, flasks, and syringes) it does not corrode sharp instruments or erode glass surfaces > this method is like baking the microbes, the heat changes the microbial proteins by oxidation reactions and creates an arid internal environment that burns them, but they must be free of oil or grease films otherwise it wont work |
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Moist Heat |
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penetrates material much more rapidly than dry heat because water molecules conduct heat better than air, and it can be used at a lower temperature and shorter exposure times than dry heat; it kills microbes by denaturation i.e. Boiling water (but it is not a sterilizing agent because the destruction of bacterial spores and the inactivation of viruses cannot be assured) (Bacterial spores require 2+ hours, many require just 30 mins) |
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Denaturation |
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A process caused by heat or pH in which proteins lose their function due to changes in their 3D structure; they revert to their 2D structure, they coagulate and become nonfunctional, which requires less energy than oxidation and less heat needs to applied |
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Pressurized Steam |
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most dependable method for sterilization including the destruction bacterial spores; moist heat is the sterilizing agent not the pressure |
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Autoclave |
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An instrument used to sterilize microbiological material by means of high temperatures using steam under pressure > when pressure of a gas increases, the temperature of the gas increases proportionally because it is a closed system > As water molecules in steam become more energized, their penetration increases substantially > contains a sterilizing chamber into which articles are placed and a steam jacket where steam is maintained, where steam flows and values increase the pressure to above normal, and the temperature rises to 121OC and the superheated steam rapidly conducts heat into microorganisms > for most resistant bacterial species 15 mins is needed for destruction; for denser or larger objects more than 30 mins is needed > used in hospitals and labs to control microorganisms; in hospitals, blankets, intravenous solutions, bedding, utensils, instruments, and more are put in this; labs use it to sterilize bacteriological media and destroy pathogenic cultures > it is safe for glassware and metalware but not for plasticware since it melts, and sharp instruments since they will dull, and oily substances since they don’t mix with water |
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Prevacuum Autoclave |
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An instrument that uses saturated steam at high temperature and pressure for short time periods to sterilize materials; reaches temperatures of 132-134OC and a pressure of 28-30 lb/in2 so the time is reduced to mins > needs less time to sterilize and complete the cycle |
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Tyndallization/Fractional Sterilization |
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A sterilization method in which materials are heated in free flowing steam for 30 mins on each of three successive days; a fraction of the sterilization process was completed in a day; requires that spores be in a suitable medium, like broth to germinate; sterilizes high tech instruments and new chemical substances |
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Day 1 |
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steam kills virtually all organisms except bacterial spores |
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Day 2 |
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Overnight incubation, the spores germinate and the viable cells multiply only to be killed on the second day at 100OC exposure |
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Day 3 |
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materials are cooled and any remaining spores germinate, and then are killed on third day |
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Pasteurization |
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A heating process that destroys pathogenic bacteria in a fluid such as milk and lowers the overall umber of bacterial cells in the fluid (spores are not affected) |
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Holding (Hatch) Method |
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A pasteurization process that exposes a liquid to 62.9OC for 30 min. > used to eliminate Mycobacterium tuberculosis, Coxiella burnetii (Q fever), Salmonella, and Escherichia coli from milk, fruit juices, and other > thermophilic bacteria thrive at this temperature but they cannot grow in body temperatures |
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Flash Pasteurization Method (HTST) |
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A treatment in which milk is heated at 71.6OC for 15 sec. and then cooled rapidly to eliminate harmful bacteria |
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Ultra High Temperature (UHT) Method |
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A treatment in which milk is heated at 82OC for 3 seconds to destroy pathogens |
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Filtration |
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A mechanical method to remove microorganisms by passing a liquid or air through a filter |
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Membrane Filter |
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A pad of cellulose acetate or polycarbonate > As fluid passes through the filter, organisms are trapped in the pores of the filtering material. The solution dripping through the filter into the receiving container is decontaminated or in some cases sterilized, >used to purify such heat-sensitive liquids as beverages, some bacteriological media, toxoids, may pharmaceuticals, and blood solutions > valuable because bacterial cells trapped on the filter multiply and form colonies on the filter pad when the pad is placed on a plate of culture medium, then the colonies can be counted to determine the number of originally present |
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High Efficiency Particulate Air (HEPA) Filter |
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consists of a mat of randomly arranged fibers that trap particles, microorganisms, and spores, trap 99% of all particles, including microorganisms, spores with a diameter larger than 0.3 µ > used in hospital wards, like burn unit, to filter microorganism, > in some hospital wards like respiratory diseases and in pharmaceutical filling rooms, the air is recirculated to ensure purity |
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High Efficiency Particulate Air (HEPA) Filter |
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consists of a mat of randomly arranged fibers that trap particles, microorganisms, and spores, trap 99% of all particles, including microorganisms, spores with a diameter larger than 0.3 µ > used in hospital wards, like burn unit, to filter microorganism, > in some hospital wards like respiratory diseases and in pharmaceutical filling rooms, the air is recirculated to ensure purity |
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Biological Safety Cabinet |
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A cabinet or hood used to prevent contamination of biological materials |
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Ultra Violet (UV) light |
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A type of electromagnetic radiation of short wavelengths that damages DNA; wavelength 100-400 nm, with energy at about 265 nm most destructive to bacterial cells > when microorganisms are exposed, cellular DNA absorbs the energy, and adjacent thymine molecules (in the same strand) link together, kinking the double helix and disrupting DNA replication, so the organism is damaged so that they can no longer produce critical proteins or reproduce, and it dies > reduces microbial populations when in direct exposure, it limits airborne or surface contamination in hospital rooms, morgue, pharmacy, toilet facility, or food operation |
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X-Ray |
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An ionizing radiation that can be used to sterilize objects; wavelengths shorter than UV light, force electrons out of their shells creating ions |
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Gamma Rays |
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an ionizing radiation that can be used to sterilize objects; wavelengths shorter than UV light, force electrons out of their shells creating ions |
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Ionizing Radiations |
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A type of radiation such a gamma rays and X rays that causes the separation of atoms or a molecule into ions > ions quickly combine, mainly with cellular water, and the free radicals generated affect cell metabolism and physiology > used to sterilize pharmaceuticals (vitamins, hormones, and antibiotics) and plastics and suture materials; it is also used to preserve food |
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Pasteurizing Dose |
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the amount of irradiation used to eliminate pathogens > to eliminate the pathogens used on meats, poultry, and other foods |
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Microwaves |
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wavelengths longer than UV and visible light, they are absorbed by water molecules, and the heat of friction from these excited molecules is transferred from foods |
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Drying |
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has been a way to preserve various meats, fish, cereals, and other foods, without water there is no life, making it nonperishable, this is achieved by salt |
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Salting |
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has been a way to preserve and its based on osmotic pressure, when food is salted usually sodium chloride water diffuses out of microorganisms to the higher salt concentration and lower water concentration in the surrounding environment, leaving the microorganisms dehydrated and die [Same thing occurs to sugared foods (usually sucrose) like syrups, jams, and jellies] |
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Osmotic Pressure |
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the pressure applied to a solution to stop the inward diffusion (osmosis) of a solvent through a semi-permeable membrane |
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Low Temperatures |
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found in the refrigerator and freezer retard spoilage by lowering the metabolic rate of microorganisms and their rate of growth |
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Tincture |
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A substance dissolved in alcohol > during the civil war, a tincture of iodine was used as an antiseptic for soldiers and Joseph Lister established the principles of aseptic surgery using carbolic acid for treating wounds |
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Disinfection |
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the process of killing or inhibiting the growth of pathogens |
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Disinfectant |
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A chemical used to kill or inhibit pathogenic microorganisms on a lifeless object such as a tabletop |
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Antiseptic |
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A chemical used to reduce or kill pathogenic microorganisms on a living organism, like the surface of the human body |
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Antiseptics and Disinfectants |
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inactivate the major enzymes of an organism and interfere with its metabolism so that it dies, A chemical also may be microbiostatic, disrupting minor chemical reactions and slowing the metabolism, results in a longer time between cell divisions |
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Sepsis |
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The growth and spreading of bacteria or their toxins in the blood and tissues |
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Septicemia |
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A growth and spreading of bacterial cells in the blood stream |
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Asepsis |
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The process or method of bringing about a condition in which no unwanted microbes are present |
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Sanitize |
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referring to the reduction of a microbial population to a safe level i.e. in dairy and food processing plants, the equipment usually is sanitized through the process of sanitization |
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Degerm |
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To mechanically remove organisms from a surface |
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1.) Able to kill or slow the growth of a microorganims 2.) Nontoxic to animals or humans, especially if it is used as an antiseptic 3.) Soluble in water and have a substantial shelf life during which its activity is retained 4.) Useful in much diluted form and able to perform its job in a relatively short time |
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Useful Properties of Disinfectants or Antiseptics (4) |
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1.) Temperature: it is important to know at what temperature the disinfection is to take place because a chemical reaction occurring at 37OC (body temperature) may not occur at 25OC (room temperature) 2.) pH: A particular chemical may be effective a certain pH but not another 3.) Stability: the chemical reaction may be very rapid with one agent and slower with another. Thus, if long term disinfection is desired, the second agent may be preferable |
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Chemical Parameters for Disinfectants and Antiseptics |
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Phenol Coefficient (PC) |
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A number that indicates the effectiveness of an antiseptic or disinfectant compared to phenol > higher than 1 is more effective than phenol > lower than 1 is less effective than phenol > determined by a laboratory procedure in which dilutions of phenol and the test chemical are mixed with standardized bacterial species like Staphylococcus aureus, Salmonella typhi; laboratory tech then determines which dilutions have killed the organisms after a 10-min exposure but not after a 5 min. exposure > Cons: performed in lab rather than real life situation, does not take account factors cited above, like tissue toxicity, activity in the presence of organic matter, or temperature variations |
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In Use Test |
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A procedure used to determine the value of a disinfectant or antiseptic i.e. swab samples from a floor are taken before and after the application of a disinfectant to determine the level of disinfection |
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Halogens |
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A chemical element whose atoms have seven electrons in their outer shell; ie iodine and chlorine; believed to cause the release of atomic oxygen, which tehn combines with and inactivates certain cytoplasmic proteins like enzymes, killing occurs within 30 mins |
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Chlorine |
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available in a gaseous form and as both organic and inorganic compounds, used in municipal water supplies and swimming pool, keeping microbial populations low; |
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sodium hypochlorite (Na+[OCl]-) or calcium hypochlorite (Ca2+ [OCl]-) (chlorinated lime) Hypochlorite Compounds |
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cause cellular proteins to clump together, destroying their function, used to disinfect clear water for drinking, very dilute solutions for sanitizing commercial and factory equipment |
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Chloramines |
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like Chloramine-T are organic compounds used as bactericides and for disinfecting drinking water |
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Iodine (I) |
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slightly larger than chlorine atom and is more reactive and more germicidal, A tincture of it is antiseptic for wounds, 2% of it, it can disinfect water, sanitizes restaurant equipment and eating utensils |
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Iodophors |
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A complex of iodine and detergents that is used as an antiseptic and disinfectant > these water-soluble complexes release iodine over a long period of time and have the added advantage of not staining fabrics or tissues; the solubilizing agent loosens the organisms from the surface and diatomic iodine (I2) irreversibly damages the microbe by reacting with enzymes in the respiratory chain and with proteins in the cell membranes and cell wall > i.e. Wescodyne (preoperative skin preparations) Betadine (local wounds) Povidone, stabilizes the iodine and releases slowly > can combined with nondetergent carrier molecules |
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Phenol |
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A chemical compounds that has one or more hydroxyl groups attached to a benzene ring and derivatives are used as an antiseptic or disinfectant (carbolic acid) > played a key role in Lister’s disinfection practices and remains a standard against which other antisepsis and disinfectants are evaluated using the phenol coefficient test >it is active against gram-positive bacteria, but its activity is reduced in the presence of organic matter > it and its derivatives act by denaturing proteins, especially in the cell membrane > it is expensive, has a pungent ordor, caustic to the skin, so it is not used as much as its derivatives greater germicidal activity and lower toxicity than parent |
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Hexylresorcinol |
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used for mouthwashes, topical antiseptics, and throat lozenges, it reduces tension, by loosening bacterial cells from tissues and allowing greater penetration of the germicidal agent |
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Biphenols |
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A combination of two phenol molecules used in disinfectants I.e. orthophenylphenol used in Lysol and amphyl and hexachlorophene used in toothpastes, underarm deordorants, and bath soaps |
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Chlorhexidine |
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an important bisphenol, used as a surgical scrub, hand wash, and superficial skin would cleaner |
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Triclosan |
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A phenol derivative incorporated as an antimicrobial agent into a wide variety of household products; fairly mild and nontoxic and is effective against pathogenic bacteria it is included in antibacterial soaps, lotions, mouthwashes, toothpastes, toys, food trays, underwear, kitchen sponges, utensils, and cutting boards > con: developing resistance to the chemical |
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Heavy Metals |
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A chemical element often toxic to microorganisms (i.e. mercury, copper, silver) • Large weights and complex electron configurations, they are reactive with proteins, particularly at the protein’s sulfhydral groups (-SH) and they are believed to bind protein molecules together by forming bridges between the groups, proteins involved are enzymes, cellular metabolism is disrupted and the microorganisms die. But they are NOT sporicidals |
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Mercury (Hg) |
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very toxic to host, and the antimicrobial activity of mercury is reduced when other organic matter is present, in such products, merbromin (Mercurochrome) and thimerosal (Methiolate), combined with carrier compounds and is less toxic when applied to the skin, especially after surgical incisions, Thimersol can be used as a preservative in vaccines |
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Copper (Cu) |
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Active agent against chlorophyll containing organisms and is a potent inhibitory of algae, Copper Sulfate (CuCO4) it is incorporated into algicides and is used in swimming pools and municipal water supplies |
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Ethyl Alcohol (Ethanol) |
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active against vegetative bacterial cells, including the tubercle bacillus, but it has no effect on spores, it denatures proteins and dissolves lipids, an action leading to cell membrane disintegration, it is a strong dehydrating agent • reacts readily with organic matter, medical instruments, and thermometers must be thoroughly cleaned before exposure > usually 10 min immersion in 50-80% alcohol solution prevents rapid evaporation • It is a popular hand sanitizer |
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Ventipuncture |
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the piercing of a vein to take blood, to feed somebody intravenously or to administer a drug Alcohol is used for this injection, it mechanically removes bacterial cells from the skin and dissolves lipids, isopropyl or rubbing alcohol has high bactericidal activity in concentration as high as 99% |
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Soaps |
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chemical compounds of fatty acids combined with potassium or sodium hydroxide usually has a pH of 8.0 and some microbial destruction is due to the alkaline conditions they establish on the skin, they are degerming agents for the mechanical removal of microorganisms from the skin surface |
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Surfactant |
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A synthetic chemical, such as a detergent, that emulsifies and solubilizes particles attached to surfaces by reducing the surface tension > remove skin oils, further reducing the surface tension, and increasing the cleaning action |
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Detergent |
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A synthetic cleansing substance that dissolves dirt and oil > cellular membrane, they also alter the membranes and encourage leakage from the cytoplasm (used to clean cutting boards to reduce the possibility of transmitting contaminants) > control microorganisms are cationic (positively charged0 derivatives of ammonium chloride; four organic radicals replace the four hydrogens and at least one radical is long hydrocarbon chain |
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Quaternary Ammonium Compounds/ Quat |
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A positively charged detergent with four organic groups attached to a central nitrogen atom used as a disinfectant (i.e. Zephiran, Ceepryn,) they are relatively stable with little odor, used as sanitizing agents for industrial equipment and food utensil, as skin antiseptics as disinfectants in mouthwashes and contact lens cleansers, and disinfectants for use in hospital walls and floor and for food preparation surfaces |
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Peroxide |
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A compound containing an oxygen-oxygen single bond |
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Hydrogen Peroxide |
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An unstable lipid that readily decomposes in water and oxygen gas (O2) > used for scrapes, wounds, and abrasions > it foams and effervesces as catalase in the tissue breaks it down, which is seen by the bubbling that loosens dirt, debris, and dead tissue and it is effective against anaerobic bacterial species more stable forms do not decompose spontaneously, and can be used topically such as inanimate material (soft contact lenses), utensils, heat-sensitive plastics, and food processing equipment within 30 mins) |
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Benzoyl Peroxide |
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at low concentrations can treat acne and an active ingredient in teeth whitening products |
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Aldehydes |
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• Agents that react with amino and hydroxyl groups of nucleic acids and proteins, which cross linking inactivates the proteins and nucleic acids |
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Formaldehyde |
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a gas at high temperatures and solid at room temperature called formalin, used as embalming fluid, but it is used for inactivating viruses in certain vaccines and producing toxoids from toxins • Cons: leaves a residue and instruments must be rinsed before use, and can cause dermatitis when contacted |
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Formalin |
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A solution of formaldehyde used as embalming fluid in the inactivation of viruses, and as a disinfectant |
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Glutaraldehyde |
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A liquid chemical used for sterilization; small organic molecule that destroys bacterial cells within 10-30 min and spores in 10 hours > materials must be precleaned, then immersed for 10 hours, rinsed thoroughly with sterile water, dried in a special cabinet with sterile air and stored in a sterile container to ensure that the material remains sterile > PROS:Does not damage delicate objects so it can disinfect or sterilize optical equipment like fiber optic endoscopes > CONS: gives off irritating fumes, and instruments must be rinse thoroughly in sterile water |
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Ethylene Oxide |
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A chemical gas that is used to sterilize many objects and instruments; a small molecule with excellent penetration capacity, microbicidal, sporicidal, used to sterilize paper, leather, wood, metal, plastics, and rubber products [catheters, artificial heart valves, heart-lung machine components, and optical equipment] used in “gas autoclaves” > CON: carcinogenic and highly explosive, cold burns on skin |
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Chlorine Dioxide |
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A gas used to sterilize objects or instruments; produces nontoxic byproducts, noncarcinogen, can be used as gas or liquid, used to decontaminate anthrax-contaminated mail and office buildings |
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Sterilization |
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involves destruction of all living microbes, spores, and viruses, objects that undergoes this process can become contaminated when exposed to air and surroundings |
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Sanitization |
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reduces the number of pathogens or discourages their growth |
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Heat |
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is one of the most common physical control methods, at temperatures above the growth range: proteins and nucleic acids are destroyed and water is removed |
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Thermal Death Time |
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The time it takes for a microbial species to die at a given temperature |
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Thermal Death Point |
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The minimum temperature at which a microbial species dies in a give time period |
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Incineration |
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uses direct flame to kill microbes |
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Dry heat |
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requres long periods of exposure to high tempeartures |
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Dry Heat |
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the heat changes microbial proteins, and removes water, slowly burning the microbes |
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Moist Heat |
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e.g. boiling water it is faster and effective at a lwoer temperature than dry heat |
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Moist Heat |
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it kills microbes by denaturing their protein |
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Boiling Water |
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may not kill all spores or inactivate all viruses |
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Pressurized Steam |
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is used in an autoclave as a more dependable way to sterilize a variety of objects |
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Prevacuum Autoclave |
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decreases cycle time and exposes of sensitive materials to steam |
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Fractional Sterilization |
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on 3 consecutive days is used for sterilization if materials are not suited to the autoclave |
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Pasteurization |
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reduces bacterial population in food and drink, reduces the chances of spoilage and disease, but bacterial spores are not affected by this process |
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Filtration |
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traps microorganisms, as fluids passes through filter organisms above certain size threshold are trapped in the pores |
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HEPA filter |
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air can be filtered using a high efficiency particular air |
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Ultra Violet Light |
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can be used to control microbial growth, causes thymine molecules to link together in DNA, errors in protein synthesis and impairment of chromosome replication occur |
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X Ray and Gamma Rays (ionizing radiation) |
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force electrons out of microbial molecules, affecting cell metabolism and physiology |
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Drying |
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removes the water necessary for microbes to live as a means to preserve and retard spoilage by microorganisms in food |
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Salting |
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causes water to diffuse out of organisms by osmosis, causing dehydration and death as a means of preserving and retarding spoilage by microorganisms in foods |
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Low Temperatures |
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lower microbial metabolic and growth rates, retarding spoilage and preserving food |
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Chemical agents |
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rarely achieve sterilization but they do disinfect (destroying pathogens) |
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Antiseptics |
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ussed to destroy pathogens on living tissues |
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Sepsis |
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contamination by microorganisms |
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Santizing |
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reducing microbial population to a safe level |
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De-Germing |
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removing organisms from an object's surface |
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1.) Able to kill or slow growth of microbes 2.) nontoxic to humans and animals 3.) soluble in water, 4.) storable, 5.) effective quickly and at low concentration |
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Antiseptics and Disinfectants should be able to do these things: (5) |
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Temperature pH Duration of disinfection |
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3 important properties to choose an agent |
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Antiseptics and Disinfectants |
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they can be evaluated for their effectiveness using Phenol Coefficient (PC) and in use test |
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Phenol Coefficient (PC) |
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indicates disinfecting ability compared to that of phenol |
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In Use Test |
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compares samples of substrate before and after disinfection |
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Halogens |
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oxidize proteins and inhibits growth (chlorine, iodine) |
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Chlorine |
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keeps bacterial populations low in municipal water supplies and swimming pools |
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Iodine |
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used to disinfect wounds, water, and restaurant equipment |
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Iodophors |
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release iodine over a long period of time |
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Phenol and phenolic compounds |
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This chemical substance and its derivatives denature proteins |
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Phenol Cons |
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it is expensive, caustic, and has a pungent odor |
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Phenol Derivatives |
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have greater germicidial activity and lower toxicity than phenol |
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Bisphenol |
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combinations of two phenol molecules, are commonly used in disinfection and antisepsis |
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Heavy Metals |
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They interfere with microbial metabolism, disrupting cellular metabolism, killing microbes; mercury, copper, and silver are reactive with proteins |
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Alcohol and Ethanol |
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it denatures proteins and disrupts membranes by causing lipid dissolution; ethanol is effective against vegetative cells but NOT SPORES, alcohol is used in many hand sanitizers |
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Soaps |
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acts as a surface active agents; remove microbes by emulsifying and solubilizing particles on the skin; disrupts membrane of microbes |
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Detergent |
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acts as surface active agents, they are surfactants, they cause cytoplasm leakage from microbial membranes (e.g. QUAT) |
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Quaternary ammonium Compounds |
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reacts with cell membranes and destroys some bacteria and virsues (because of their charge) (cationic) |
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Hydrogen Peroxide |
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damages cellular components when catalase in wounded tissues transforms it to oxygen and water, and oxygen is effective against anaerobic bacteria |
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Aldehydes |
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cause cross linking that inactivates proteins and nucleic acids; sterilization agent |
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Ethylene Oxide |
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effective sterilization agent but carcinogenic and explosive gas |
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Chlorine Dioxide |
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a non-toxic and non-carcinogenic agent that is effect for sterilization |