Chapter 11 Physical and Chemical Agents for Microbial Control PDF

Chapter 11 Physical and Chemical Agents for Microbial Control Lecture Outline See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. © McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduc...

Chapter 11 Physical and Chemical Agents for Microbial Control Lecture Outline See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. © McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. Controlling Microorganisms (1 of 2) Controlling exposure to potentially harmful microbes is essential to our lives, and it has been a concern also in the past Early protection attempts laid the foundation for microbial control methods today: – Burning wood releases formaldehyde – Herbs, perfume, and vinegar contain mild antimicrobial substances 11-2 © McGraw-Hill Education.  General Considerations in Microbial Control Physical, chemical, and mechanical methods to destroy or reduce undesirable microbes in a given area (decontamination) Primary targets are microorganisms capable of causing infection or spoilage: – Vegetative bacterial cells and endospores – Fungal hyphae and spores, yeast – Protozoan trophozoites and cysts – Worms – Viruses – Prions 11-3 © McGraw-Hill Education.  Microbial Control Methods (1 of 5) Physical agents – Heat  Dry o Incineration  Sterilization o Dry oven  Sterilization – Moist  Steam under pressure o Sterilization  Boiling water, hot water, pasteurization o Disinfection 11-4 © McGraw-Hill Education. Microbial Control Methods (2 of 5) – Radiation  Ionizing o X-ray, cathode, gamma  Sterilization  Nonionizing o UV  Disinfection 11-5 © McGraw-Hill Education. Microbial Control Methods (3 of 5) – Mechanical removal methods  Filtration o Air  Disinfection o Liquids  Sterilization – Chemical agents  Gases o Sterilization o Disinfection 11-6 © McGraw-Hill Education.  Microbial Control Methods (4 of 5)  Liquids o (Animate)  Antisepsis o (Inanimate)  Disinfection  Sterilization Disinfection: The destruction or removal of vegetative pathogens but not bacterial endospores. Usually used only on inanimate objects. Sterilization: The complete removal or destruction of all viable microorganisms. Used on inanimate objects. 11-7 © McGraw-Hill Education.  Microbial Control Methods (5 of 5) Antisepsis: Chemicals applied to body surfaces to destroy or inhibit vegetative pathogens. 11-8 © McGraw-Hill Education.  Relative Resistance of Microbes (1 of 2) Highest resistance – Prions, bacterial endospores (Bacillus, Clostridium) Moderate resistance – Protozoan cysts; naked viruses – Bacteria with no endospores but resistant walls: – Mycobacterium, Pseudomonas, Acinetobacter, other gram(-) – Staphylococcus (most heat- and chemical- resistant bacteria) 11-9 © McGraw-Hill Education.  Relative Resistance of Microbes (2 of 2) Least resistance – Most bacterial vegetative cells – Fungal spores and hyphae – Yeasts – Enveloped viruses – Protozoan trophozoites 11-10 © McGraw-Hill Education.  The Resistance of Endospores (1 of 2) TABLE 11.1 Relative Resistance of Bacterial Endospores and Vegetative Cells to Control Agents Vegetative Relative Method Endospores* Forms* Resistance** Heat (moist) 120°C 80°C 1.5x Radiation (X-ray) dosage 4,000 grays 1,000 grays 4x Sterilizing gas (ethylene oxide) 1,200 mg/l 700 mg/l 1.7x Sporicidal liquid (2% glutaraldehyde) 3 hours 10 min 18x * Values are based on methods (concentration, exposure time, intensity) that are required to destroy the most resistant pathogens in each group. This number is a comparison of the conditions required to kill ** endospores versus vegetative cells and is an average of the most resistant pathogens in each group. 11-11 © McGraw-Hill Education. Terminology and Methods of Control (1 of 2) Sterilization –process to destroy all viable microbes Microbicidal agents (germicides) – antimicrobial agent aimed at destroying a certain group of microorganisms (bactericide, fungicide, virucide, sporicidal) – Disinfection – use of a physical process or a chemical agent (disinfectant) to destroy vegetative pathogens but not bacterial endospores – Antisepsis – application of chemical agents (antiseptics) directly to exposed body surfaces, wounds, and surgical incisions to destroy or inhibit vegetative pathogens 11-12 © McGraw-Hill Education. Terminology and Methods of Control (2 of 2) Agents that cause microbistasis – antimicrobial agent aimed at temporarily prevent microbes from multiplying Methods that reduce the numbers of microorganisms – Sanitation – any cleansing technique that removes microorganisms from inanimate surfaces to reduce the potential for infection and spoilage – Degermation – reduction of microbial load from living tissue by mechanical means 11-13 © McGraw-Hill Education.  TABLE 11.2 Microbial Control Terminology Term Definition Example The destruction, removal, or reduction in Asepsis, disinfection, sanitization, Decontamination number of undesirable microbes degermation, sterilization The presence of infected wounds, blood Sepsis The growth of microorganisms in the tissues infection Techniques that prevent the entry of Cleansing the skin with iodine prior to Asepsis microorganisms into sterile tissues surgery, using sterile needles Chemicals applied to body surfaces to lodophors, antibacterial soap, Antiseptic destroy or inhibit vegetative pathogens chlorhexidine Destruction of vegetative pathogens on Disinfection 5% bleach, boiling water inanimate objects Cleansing technique that removes Sanitization microorganisms and debris from Dishwashing, laundering clothes inanimate surfaces Cleansing technique that removes Degermation microorganisms and debris from living Surgical handscrub, alcohol wipes tissue The removal or destruction of all viable Autoclaving, ionizing radiation (correctly Sterilization microbes applied) 11-14 © McGraw-Hill Education.  Microbial Death Hard to detect, microbes often reveal no conspicuous vital signs to begin with Permanent loss of reproductive capability, even under optimum growth conditions Factors that affect microbial death: – Number of microbes – Nature of microbes in the population – Temperature and pH of environment – Concentration or dosage of agent – Mode of action of the agent – Presence of solvents, organic matter, or inhibitors 11-15 © McGraw-Hill Education. Factors That Affect Death Rate 11-16 © McGraw-Hill Education.  Practical Concerns in Microbial Control Selection of method of control depends on circumstances: Does the application require sterilization? Is the item to be reused? Can the item withstand heat, pressure, radiation, or chemicals? Is the method suitable? Will the agent penetrate to the necessary extent? Is the method cost- and labor-efficient and is it safe? 11-17 © McGraw-Hill Education.  Antimicrobial Agents’ Modes of Action (1 of 4) Cellular targets of physical and chemical agents: Cell wall –becomes fragile and cell lyses (some antimicrobial drugs, detergents, and alcohol) Cell membrane – loses integrity (surfactants) 11-18 © McGraw-Hill Education. Antimicrobial Agents’ Modes of Action (2 of 4) 11-19 © McGraw-Hill Education.  Antimicrobial Agents’ Modes of Action (3 of 4) Cellular targets of physical and chemical agents: Protein and nucleic acid synthesis – prevention of replication, transcription, translation, peptide bond formation, protein synthesis (chloramphenicol, ultraviolet radiation, formaldehyde) Protein function – disrupt or denature proteins (alcohols, phenols, acids, heat) 11-20 © McGraw-Hill Education.  Concepts Check: (1) If you wipe your hands with an antimicrobial cleaner, you are accomplishing A. Sterilization B. Disinfection C. Antisepsis D. Sanitization 11-21 © McGraw-Hill Education.  Concepts Check: (2) If you wipe your hands with an antimicrobial cleaner, you are accomplishing A. Sterilization B. Disinfection C. Antisepsis D. Sanitization Answer: C 11-22 © McGraw-Hill Education.  Physical Methods of Control The vast majority of microbes are readily controlled by abrupt changes in their environment Some physical methods are: – Heat (moist and dry) – Cold temperatures – Desiccation – Radiation – Filtration 11-23 © McGraw-Hill Education.  Mode of Action and Relative Effectiveness of Heat (1 of 2) Moist heat – lower temperatures and shorter exposure time; coagulation and denaturation of proteins, which halts cellular metabolism Dry heat – moderate to high temperatures; dehydration, alters protein structure; incineration 11-24 © McGraw-Hill Education.  Mode of Action and Relative Effectiveness of Heat (2 of 2) TABLE 11.3 Comparison of Times and Temperatures to Achieve Sterilization with Moist and Dry Heat Temperature Time to Sterilize Moist Heat 121°C 15 min 125°C 10 min 134°C 3 min Dry Heat 121°C 600 min 140°C 180 min 160°C 120 min 170°C 60 min 11-25 © McGraw-Hill Education.  Thermal Death Measurements Bacterial endospores are most resistant, while vegetative states of bacteria the least Thermal death time (TDT) – shortest length of time required to kill all test microbes at a specified temperature Thermal death point (TDP) – lowest temperature required to kill all microbes in a sample in 10 minutes 11-26 © McGraw-Hill Education. Methods of Moist Heat Control (1 of 5) 1. Sterilization with Steam Under Pressure Autoclave (15 psi/121oC/10-40min) Pressure increases steam temperature Steam must reach surface of item being sterilized Item must not be heat or moisture sensitive Produces denaturation of proteins, destruction of membranes and DNA 11-27 © McGraw-Hill Education. Methods of Moist Heat Control (3 of 5) 2. Nonpressurized Steam Tyndallization – intermittent sterilization for substances that cannot withstand autoclaving Items exposed to free-flowing steam for 30–60 minutes, incubated for 23–24 hours and then subjected to steam again Repeat cycle for 3 days Used for some canned foods and laboratory media 3. Boiling Water: Disinfection Boiling at 100°C for 30 minutes to destroy non- spore-forming pathogens 11-28 © McGraw-Hill Education. Methods of Moist Heat Control (4 of 5) 4. Pasteurization Heat is applied to kill potential agents of infection and spoilage without destroying the food flavor or value – Flash method: 71.6°C, 15 sec Not sterilization – kills non-spore-forming pathogens and lowers overall microbe count; does not kill endospores or many nonpathogenic microbes – Ultrapasteurized (sterile) milk is processed (UHT) — 134°C, 2-5 sec 11-29 © McGraw-Hill Education. Methods of Moist Heat Control (5 of 5) A small flash pasteurizer used by dairies for calves’ milk. (a): Ganay Mutlu/Getty Images 11-30 © McGraw-Hill Education. Dry Heat: Hot Air and Incineration (1 of 2) Dry heat uses higher temperatures than moist heat Incineration – flame, electric heating coil, infrared incinerators – Ignites and reduces microbes and other substances – Very common practice in the microbiology lab Hot air (Dry) ovens – heated, circulated air (150oC-180oC, 12min-4h) – Coagulate proteins 11-31 © McGraw-Hill Education. Dry Heat: Hot Air and Incineration (2 of 2) © Kathy Park Talaro Dry heat incineration. Infrared incinerator with shield to prevent spattering of microbial samples during flaming. 11-32 © McGraw-Hill Education.  Using Heat for Sterilization and Disinfection (1 of 3) TABLE 11.4 Applications Using Heat for Sterilization and Disinfection Medical and Commercial Uses and Form of Heat Equipment Temperature/Time Limitations Moist heat: Employs steam, boiling, or hot water; mode of action coagulates proteins Sterilization of heat-resistant materials Autoclave, pressure cooker; made of glass, cloth, rubber, metal; 121°C, pressure of 15 psi for media; a few plastics; canned food, Steam under pressure 10 to 40 minutes, depending spices. Decontamination of cultures. on load size; kills endospores. Not appropriate for moisture- repellent oil or powder. Arnold's Sterilizer—100°C for 30 Limited uses in sterilizing some media minutes on 3 days; items are and foods that cannot be Unpressurized steam incubated between autoclaved; can be used to disinfect (tyndallization) treatments to allow but not sterilize some medical endospores to germinate. supplies 11-33 © McGraw-Hill Education.  Using Heat for Sterilization and Disinfection (2 of 3) The “TABLE 11.4” continues on this slide. Equipment Medical and Commercial Uses Form of Heat Temperature/Time and Limitations Disinfection of milk and dairy products to destroy milk-borne Pasteurizer; flash method pathogens; UHT can sterilize for works at 71.6°C for 15 longer shelf life. Fruit juices, Pasteurization seconds; ultrahigh beer, and wine may be temperature (UHT) uses pasteurized to destroy 134°C for a few seconds. contaminants and preserve the products. Limited to disinfection and Water bath or pan heated to sanitization of heat-resistant 100°C; items are placed household objects such as eating Boiling water in water for 30 minutes utensils, clothing, sick room to kill vegetative supplies, baby supplies, bedding, pathogens. and water in emergencies; problem with recontamination 11-34 © McGraw-Hill Education.  Using Heat for Sterilization and Disinfection (3 of 3) The “TABLE 11.4” continues on this slide. Equipment Medical and Commercial Uses and Form of Heat Temperature/Time Limitations Dry heat: Employs dried hot air, flame, or heat coil; works by dehydration or combustion Materials that can withstand hot Electric or gas chamber temperatures and dehydration; Dry oven heated to 150°C to 180°C glassware, metals, powders, oils. Poor for 2 to 4 hours choice for liquids, rubber, plastics; time- consuming. Furnaces, incinerators up to 6,500°C For sterilizing tips of inoculation instruments; Bunsen burner flame up to limited to high-temperature metals. Incineration 1,800°C; small infrared Permanent disposal of waste material incinerators to 800°C from laboratories; burning reduces bulky packages and garbage to ashes. For permanent disposal only. 11-35 © McGraw-Hill Education.  Effects of Cold and Desiccation Cold – Microbiostatic – slows the growth of microbes – Refrigeration 0–15oC and freezing < 0oC – Used to preserve food, media, and cultures Desiccation – Gradual removal of water from cells, leads to metabolic inhibition – Not effective microbial control – many cells retain ability to grow when water is reintroduced – Lyophilization – freeze drying; preservation 11-36 © McGraw-Hill Education.  Concepts Check: (3) Which of the following accomplishes microbiocidal effects? A. Boiling B. Pasteurization C. Incineration D. Freezing E. Desiccation 11-37 © McGraw-Hill Education.  Concepts Check: (4) Which of the following accomplishes microbiocidal effects? A. Boiling B. Pasteurization C. Incineration D. Freezing E. Desiccation Answer: A, B, and C 11-38 © McGraw-Hill Education.  Physical Methods of Control: Radiation (1 of 2) Radiation: Energy emitted from atomic activities and dispersed at high velocity through matter or space Types of radiation suitable for microbial control: 1. Ionizing radiation  Gamma rays  X rays  Cathode rays 2. Noniodizing radiation  Ultraviolet (UV) radiation 11-39 © McGraw-Hill Education. Cellular Effects of Irradiation (1 of 4) 1. Ionizing radiation – deep penetrating power sufficient energy to cause electrons to leave their orbit – Gamma rays, X rays, cathode rays – Breaks DNA 2. Nonionizing radiation – little penetrating power – UV light creates pyrimidine dimers – Interferes with replication 11-40 © McGraw-Hill Education.  Radiation Use for Sterilization and Disinfection (1 of 4) TABLE 11.5 Applications Using Radiation for Sterilization and Disinfection Form of Equipment/Mode of Action Medical and Commercial Uses and Limitations Radiation Ionizing Cobalt radiation gives off Cold sterilization of packaged products such as radiation gamma rays; others are X medical supplies and instruments that cannot be rays, cathode rays. Rays heat sterilized Sporicidal and fragment DNA and create penetrating Sterilization of foods, including fruits, lettuce and ionized bases; highly spinach, grains, spices, meats, and packaged mutagenic. meals Sterilization of drugs and vaccines Rapid and penetrating, prevents infection and spoilage 11-41 © McGraw-Hill Education.  Radiation Use for Sterilization and Disinfection (2 of 4) The “TABLE 11.5” continues on this slide. Form of Equipment/Mode of Action Medical and Commercial Uses and Limitations Radiation Nonionizing Germicidal lamps or Mostly disinfection of air, some liquids, a few solids; ultraviolet generators set to deliver reduces airborne pathogens in medical and (UV) UV rays from 240 to 280 dental offices, hospital rooms, and operating radiation nm in wavelength; action rooms creates abnormal bonds Sporicidal and Commercial use for clean rooms, food processing between adjacent nonpenetratin areas thymines and cytosines g and produces deletion Works on liquids such as water, milk, drugs, mutations on DNA. vaccines if exposed to UV in thin layers Solid materials such as room surfaces, foods, tissue grafts, drugs, and instruments Lack of penetration through solids limits applications; direct exposure can be dangerous to eyes and skin. 11-42 © McGraw-Hill Education. Radiation Use for Sterilization and Disinfection (3 of 4) The “TABLE 11.5” continues on this slide. Source: Pacific Northwest National Laboratory Pallets of apples are being irradiated with a cobalt 60 machine that emits gamma rays. 11-43 © McGraw-Hill Education. Radiation Use for Sterilization and Disinfection (4 of 4) The “TABLE 11.5” continues on this slide. Courtesy of Violight Tabletop chamber generates ultraviolet rays to disinfect a toothbrush. 11-44 © McGraw-Hill Education. Physical Methods of Control: Filtration (1 of 2) 11-45 © McGraw-Hill Education.  Physical Methods of Control: Filtration (2 of 2) Filtration: Physical removal of microbes by passing a gas or liquid through filter Used to sterilize heat sensitive liquids and air in hospital isolation units and industrial clean rooms Source: Janice Haney Carr/CDC 11-46 © McGraw-Hill Education. Chemical Agents in Microbial Control Disinfectants, antiseptics, sterilants, degermers, and preservatives Some desirable qualities of germicides: – Rapid action in low concentration – Solubility in water or alcohol, stable – Broad spectrum, low toxicity – Penetrating – Noncorrosive and nonstaining – Affordable and readily available 11-47 © McGraw-Hill Education. Levels of Chemical Decontamination High-level germicides – kill endospores; may be sterilants – Devices that are not heat-sterilizable and intended to be used in sterile environments (body tissue) Intermediate-level – kill fungal spores (not endospores), tubercle bacillus, and viruses – Used to disinfect devices that will come in contact with mucous membranes but are not invasive Low-level – eliminate only vegetative bacteria, vegetative fungal cells, and some viruses – Clean surfaces that touch skin but not mucous membranes 11-48 © McGraw-Hill Education.  Factors that Affect Germicidal Activity of Chemicals Nature of the material being treated Degree of contamination Time of exposure required Concentration of the chemical agent. Strength and chemical action of the germicide expressed in various ways (dilution factor (ppm), dilution percentage) 11-49 © McGraw-Hill Education.  Chemical Agents Used in Health Care (1 of 4) TABLE 11.6 Qualities of Chemical Agents Used in Health Care Level of Target Agent Germicidal Toxicity Comments Microbes Activity Gas is highly Sporicidal toxic; Inactivated by organics; Chlorine Intermediate (slowly) solution unstable in sunlight irritates skin Can irritate Sporicidal Iodine Intermediate tissue; toxic Iodophors* are milder forms (slowly) if ingested Can be absorbed by Some bacteria, Low to Phenolics skin; can Poor solubility; expensive viruses, fungi intermediate cause CNS damage Most bacteria, Low to Fast-acting, mild, has Chlorhexidine* some Low toxicity intermediate residual effects viruses, fungi 11-50 © McGraw-Hill Education.  Chemical Agents Used in Health Care (2 of 4) The “TABLE 11.6” continues on this slide. Level of Target Agent Germicidal Toxicity Comments Microbes Activity Most bacteria, Toxic if ingested; a Flammable, fast- Alcohols viruses, Intermediate mild irritant; dries acting fungi skin Hydrogen Improved stability; High Toxic to eyes; toxic if peroxide,* Sporicidal works well in (sterilant) ingested stabilized organic matter Some Weak solutions Irritating to mucous Quaternary bactericidal, Low to can support membranes; ammonium virucidal, intermedi microbial poisonous if taken compounds fungicidal ate growth; easily internally activity inactivated Certain very Nontoxic; few if any Used for removing Soaps sensitive Very low toxic effects soil, oils, debris species Highly toxic if Weakly Mercurials Low ingested, inhaled, Easily inactivated microbistatic absorbed 11-51 © McGraw-Hill Education.  Chemical Agents Used in Health Care (3 of 4) The “TABLE 11.6” continues on this slide. Level of Target Agent Germicidal Toxicity Comments Microbes Activity Silver nitrate Bactericidal Low Toxic, irritating Discolors skin Can irritate skin; Not inactivated by High Glutaraldehyde* Sporicidal toxic if organic matter; (sterilant) absorbed unstable less toxic than Ortho- Sporicidal, with Intermediate glutaraldehyde, Mild, no odor phthaldehyde* time to high highly stable, stains skin Explosive in pure Very dangerous state; good Ethylene oxide High Sporicidal to eyes, lungs; penetration; gas* (sterilant) carcinogenic materials must be aerated Weakly Stains materials, Dyes bactericidal, Low Low toxicity skin fungicidal 11-52 © McGraw-Hill Education.  Chemical Agents Used in Health Care (4 of 4) The “TABLE 11.6” continues on this slide. * These chemicals approach the ideal by having many of the following characteristics: broad spectrum, low toxicity, fast action, penetrating abilities, residual effects, stability, potency in organic matter, and solubility. 11-53 © McGraw-Hill Education.  Germicidal Categories Halogens Phenolics Chlorhexidine Alcohols Hydrogen peroxide Aldehydes Gases Detergents & soaps Heavy metals Dyes Acids and Alkalis 11-54 © McGraw-Hill Education.  Halogens (1 of 2) The halogens used in germicidal preparations are: Chlorine – Cl2, hypochlorites (chlorine bleach), chloramines – Denaturate proteins by disrupting disulfide bonds – Intermediate level – Unstable in sunlight, inactivated by organic matter – Water, sewage, wastewater, inanimate objects 11-55 © McGraw-Hill Education.  Halogens (2 of 2) Iodine - I2, iodophors (betadine) – Interferes with disulfide bonds of proteins – Intermediate level – Milder medical and dental degerming agents, disinfectants, ointments 11-56 © McGraw-Hill Education.  Applications of Halogens (1 of 4) TABLE 11.7 Applications of Halogen Compounds Form of Chlorine Primary Applications How Delivered/Concerns Chlorination to a concentration of 0.6 Large-scale disinfection of drinking to 1.0 parts of chlorine per million Chlorine Gas (Cl2) water, sewage, and wastewater. parts of water destroys most vegetative pathogens.* Used extensively in sanitization and disinfection of food equipment, Common household bleach is a 5% treatment of swimming pools, spas, Hypochlorites (HClO) solution of sodium hypochlorite; drinking water, and fresh foods; for Bleach dilutions of 1:10-1:1,000 are highly wound antisepsis and routine effective germicides. medical and household disinfection, deodorizing, and stain removal. Because standard gas chlorination of An alternative to pure chlorine in water is now believed to produce Chloramines treating water supplies; also as unsafe levels of trihalomethanes, (Dichloramine, sanitizers and disinfectants; for some water districts are required Halazone) treating wounds and skin surfaces. to use chloramine treatment of water supplies. 11-57 © McGraw-Hill Education.  Applications of Halogens (2 of 4) The “TABLE 11.7” continues on this slide. Form of Iodine Primary Applications How Delivered/Concerns A complex of iodine and a Most common iodine for skin and neutral protein polymer mucous membranes; antiseptic provides slow release and prep for surgery and injections; reduced toxicity or irritation for surgical handscrubs; to lodophors of tissues; less prone to disinfect equipment and staining. Common products surfaces; possibly for burns; and are povidone-iodine (PVI; may be an alternative preventive Betadine), which contain 2% for eye infections in newborns. to 10% available iodine. Topical antiseptic prior to surgery; Weak solutions of 1% to 3% in sometimes for burned or injured water or in alcohol tinctures. Elemental Iodine: skin. Medium–level disinfection Aqueous solutions or tinctures of Aqueous or for plastic instruments, 5% to 10%; somewhat limited Tinctures thermometers; tablet form by their toxicity and tendency available for disinfection of to stain. contaminated water. Some cyst-forming protozoans such as Giardia and * Cryptosporidium can survive this level of chlorination. 11-58 © McGraw-Hill Education.  Applications of Halogens (3 of 4) The “TABLE 11.7” continues on this slide. Source: Paul Pierlott, USDA-ERRC/VGT Cantaloupes are disinfected with chlorine treated water to kill Salmonella carried on their surfaces. 11-59 © McGraw-Hill Education.  Applications of Halogens (4 of 4) The “TABLE 11.7” continues on this slide. BSIP/Universal Images Group/Getty Images Patient has been treated with a povidone-iodine solution in preparation for surgery. 11-60 © McGraw-Hill Education.  Phenols and Its Derivatives (1 of 2) Phenol (carbolic acid) is an acrid, poisonous compound Disrupt cell walls and membranes and precipitate proteins Low to intermediate level Bactericidal, fungicidal, virucidal (not sporicidal) – Lysol and Triclosan – antibacterial additive to soaps Toxicity of phenolics makes them a questionable choice as antiseptics 11-61 © McGraw-Hill Education.  Chlorhexidine A surfactant and protein denaturant with broad microbicidal properties Low to intermediate level Hibiclens, Hibitane Used as skin degerming agents for preoperative scrubs, skin cleaning, and burns 11-62 © McGraw-Hill Education. TABLE 11.8 Applications of Phenolics and Chlorhexidine (1 of 2) Form of Phenolic Primary Applications How Delivered/Concerns 1% to 3% emulsions that are Common household version of combined with soap; can be too phenol; for low or intermediate Creolin toxic for antisepsis: tend to be levels of disinfection in rooms, absorbed by membranes into the floors, and veterinary clinics. blood. Orthophenyl phenol is a major ingredient in fungicides. This same Widely employed commercially, Bisphenols phenolic is also found in some clinically, and in the home. disinfectants used in the hospital and laboratory. Formerly a widespread additive of When hexachlorophene was found to Hexachlorophene cleansing soaps (pHisoHex) for be absorbed through the skin and hospital and home use; may be a cause of neurological damage, it used to control outbreaks of was no longer available without a skin infections. prescription. It acts as both disinfectant and Widely used antibacterial antiseptic and is broad-spectrum in Triclosan compound added to soaps, its effects. New uses include (Dichlorophenoxyphenol) cosmetics, and many other surgical preps, handwashing, and household products. bathing patients. 11-63 © McGraw-Hill Education. TABLE 11.8 Applications of Phenolics and Chlorhexidine (2 of 2) Form of Primary Applications How Delivered/Concerns Chlorhexidine Alcoholic or aqueous solutions Complex base containing chlorine are now commonly used for and two phenolic rings; mode of hand scrubbing, preparing action targets cell membranes skin sites for surgical and protein structure. At incisions and injections, and moderate to high Chlorhexidine patient cleansing. concentrations, destroys both (Hibiclens, Solutions also serve as an gram-positive and gram- Hibitane) obstetric and neonatal wash, negative bacteria but not a wound degermer, a mucous spores. It may be fungicidal and membrane irrigant, and a virucidal. It is milder and less preservative for eye toxic than phenolics and is not solutions. absorbed into the skin. 11-64 © McGraw-Hill Education.  Concepts Check: (5) Which of the following is NOT true about hypochlorites (chlorine)? A. Kills by denaturing proteins B. It is light sensitive C. It is often used for disinfecting water D. It slows the release of iodine 11-65 © McGraw-Hill Education.  Concepts Check: (6) Which of the following is NOT true about hypochlorites (chlorine)? A. Kills by denaturing proteins B. It is light sensitive C. It is often used for disinfecting water D. It slows the release of iodine Answer: D 11-66 © McGraw-Hill Education.  Alcohols (1 of 2) Only ethyl and isopropyl are suitable for microbial control Intermediate level – Concentrations of 50% and higher dissolve membrane lipids and coagulate proteins of vegetative bacterial cells and fungi – Water is needed for proteins to coagulate, thus alcohol shows a greater microbicidal activity at 70% concentration than at 100% 11-67 © McGraw-Hill Education.  Alcohols (2 of 2) BELMONTE/BSIP SA/Alamy Stock Photo A nurse takes advantage of an alcohol gel hand cleansing station. These are very common in hospitals and clinics to encourage hand antisepsis. 11-68 © McGraw-Hill Education.  Hydrogen Peroxide (1 of 2) Produce highly reactive hydroxyl-free radicals that damage protein and DNA while also decomposing to O2 gas – toxic to anaerobes Antiseptic at low concentrations; strong solutions are sporicidal 11-69 © McGraw-Hill Education.  Hydrogen Peroxide (2 of 2) © Kathy Park Talaro Disinfection of contact lenses with peroxide-based cleaner. Note the bubbles produced, indicating the release of oxygen gas. 11-70 © McGraw-Hill Education.  Applications of Alcohols and Peroxides (1 of 2) TABLE 11.9 Applications of Alcohols and Peroxides (and Other Oxidizing Agents) 11-71 © McGraw-Hill Education.  Applications of Alcohols and Peroxides (2 of 2) The “TABLE 11.9” continues on this slide. Form of Primary Applications How Delivered/Concerns Aldehyde* Ethyl Alcohol Skin degerming agent and Solutions of 70% to 95% are (Ethanol, Grain antiseptic; surfactant action germicidal, inexpensive, Alcohol) removes skin oil, soil, and some nonirritating; limited by its microbes sheltered in deeper skin rate of evaporation. Items layers; occasionally used to need to be first cleaned and disinfect electrodes and face then soaked in alcohol for masks. 15 to 20 minutes. Isopropyl Alcohol Some disinfection of objects, More microbicidal and less (Rubbing surfaces; limited skin cleansing. expensive than ethanol, but Alcohol) these benefits must be weighed against its toxicity; inhaling its vapors can adversely affect the nervous system. 11-72 © McGraw-Hill Education.  Aldehydes (1 of 2) Kill by alkylating protein and DNA – Glutaraldehyde  In 2% solution (Cidex)  High level  Used as sterilant for heat sensitive instruments – Formaldehyde  Formalin – 37% aqueous solution  Intermediate to high level  Disinfectant, preservative, toxicity limits use 11-73 © McGraw-Hill Education.  Aldehydes (2 of 2) Jennifer Santolla/Alamy Stock Photo Technician treats surgical instruments with glutaraldehyde prior to heat sterilization. 11-74 © McGraw-Hill Education.  Gases and Aerosols (1 of 3) Strong alkylating agents: Ethylene oxide (ETO), propylene oxide (PO), and chlorine dioxide High level Sterilize and disinfect plastics and prepackaged devices, foods 11-75 © McGraw-Hill Education. Gases and Aerosols (2 of 3) 11-76 © McGraw-Hill Education.  Gases and Aerosols (3 of 3) Courtesy of Printpack, Inc. Examples of prepackaged medical supplies sterilized in an ethylene oxide sterilizer 11-77 © McGraw-Hill Education.  TABLE 11.10 Applications of Aldehydes and Sterilant Gases (1 of 2) Form of Aldehyde Primary Applications How Delivered/Concerns A sterilant for materials usually damaged by heat. Solutions diluted to 2% are relatively Examples include mild but require 2 to 4 hours' respiratory therapy soaking. Usual commercial equipment, hemostats, products are Cidex, Sporocidin. Glutaraldehyde fiberoptic endoscopes, Instrument sterilization involves kidney dialysis equipment, precleaning along with and dental instruments; an autoclaving to inactivate hepatitis alternate vaccine B and other blood-borne viruses. preservative, and sanitizer for poultry carcasses. Ortho- High-level disinfectant similar Faster acting and more stable than phthalaldehyde in uses and effects to glutaraldehyde but less sporicidal. (OPA) glutaraldehyde. 11-78 © McGraw-Hill Education.  TABLE 11.10 Applications of Aldehydes and Sterilant Gases (2 of 2) Form of Gas Primary Applications How Delivered/Concerns An official sterilant for heat-sensitive Carboxide and cryoxide are commercial plastics and delicate instruments in products; gas is explosive and must be used Ethylene hospitals and industries— with a stabilizer; ETO is rather toxic to Oxide prepackaged medical supplies and humans; penetrating but slow, requiring 1 (ETO) disposable Petri dishes; used to 3 hours of exposure inside a special extensively to disinfect foods, chamber. spices, dried fruits, and drugs. Physical properties and mode of action similar Propylene Sterilization of foods such as nuts, to ETO but safer because it breaks down Oxide powders, starches, and spices. into a relatively harmless substance. Air and surface sterilant; for treatment of water, food- Similar in action to ETO but does not require a Chlorine processing equipment, and chamber; thus, effective for large spaces or Dioxide medical waste; decontamination of objects. whole rooms and space probes. 11-79 © McGraw-Hill Education.  Detergents and Soaps (1 of 2) Detergents: Polar molecules, surfactant – Quaternary ammonia compounds (quats) act as surfactants that alter membrane permeability of some bacteria and fungi – Very low level Soaps: alkaline compounds – Mechanically remove soil and grease containing microbes – Weak microbicides, destroy only highly sensitive forms (gonorrhea, meningitis, and syphilis) 11-80 © McGraw-Hill Education.  TABLE 11.11 Applications of Detergents and Soaps (1 of 3) Form of Detergents or Primary Applications How Delivered/Concerns Soaps Names include benzalkonium chloride Mixed with cleaning agents to Quaternary (Zephiran), the active ingredient in disinfect and sanitize floors, Ammonium Lysol spray, and cetylpyridinium equipment surfaces, and Compounds chloride (Ceepryn); in dilutions restrooms; for sanitizing restaurant (Quats) ranging from 1:100 to 1:1,000; the utensils, food-processing level of disinfection is too low for Benzalkonium equipment, and clothing; common disinfecting medical instruments. chloride preservatives in ophthalmic Quats are active ingredients in many solutions and cosmetics. household disinfectant sprays. Alkaline salts of fatty acids; weak Cleansing agents and sanitizers in germicides with superior sudsing and industry and the home; preparing wetting properties; can remove large instruments for heat sterilization; amounts of surface soil, grease, and degerming patients' skin, routine other debris; antimicrobial chemicals hand washing by medical and added to make germicidal soaps with Soaps dental personnel, surgical and greater disinfection power. preoperative hand scrubbing. Quick Search: Go to CDC TV and watch Proper hand washing with soap is one the video “Put Your Hands Together” of the most important control about the importance of hand methods for health care and washing. personal hygiene. 11-81 © McGraw-Hill Education.  Concepts Check: (7) Which of the following kills by producing oxygen radicals? A. Alcohol B. Hydrogen Peroxide C. Aldehydes D. Gases E. Soaps 11-82 © McGraw-Hill Education.  Concepts Check: (8) Which of the following kills by producing oxygen radicals? A. Alcohol B. Hydrogen Peroxide C. Aldehydes D. Gases E. Soaps Answer: B 11-83 © McGraw-Hill Education.  Heavy Metals (1 of 2) Solutions of silver and mercury kill vegetative cells in low concentrations by inactivating proteins Oligodynamic action (having antimicrobial effects in exceedingly small amounts) Low level Merthiolate, silver nitrate, silver 11-84 © McGraw-Hill Education. Heavy Metals (2 of 2) © Kathy Park Talaro 11-85 © McGraw-Hill Education.  TABLE 11.12 Applications of Heavy Metals Form of Metal Primary Applications How Delivered/Concerns Tinctures (0.001% to 0.2%) are fairly Thimerosal (Merthiolate) and effective but a poor choice for nitromersol (Metaphen) are weak broken skin because they are toxic Organic Mercury antiseptics and infection and can delay healing. preventives; can be preservatives in Mercurochrome is now considered cosmetics and ophthalmic solutions. one of the poorest of antiseptics. Added to dressings, it effectively Silver Sulfadiazine A yellow ointment containing silver prevents infection in second- and Ointment salts and a sulfa drug. third-degree burn patients. 1% to 2% solutions have been used as Primarily as a topical germicide for antiseptics, but they discolor skin Sliver Nitrate (AgNO3) mouth ulcers and occasionally root and other tissues. canals. Incorporated into catheters to prevent urinary tract infections in the hospital; added to paint, plastics, Metallic Silver and steel as a way to control microbial survival on items such as toilet seats, stethoscopes, and even walls and floors in homes. Mild germicidal ointments or rinses for Colloidal Silver the mouth, nose, eyes, and vagina. 11-86 © McGraw-Hill Education.  Dyes as Antimicrobial Agents Aniline dyes are very active against gram- positive species of bacteria and various fungi Sometimes used for antisepsis and wound treatment Low level, narrow spectrum of activity 11-87 © McGraw-Hill Education.  Acids and Alkalis Low level of activity – Organic acids prevent spore germination and bacterial and fungal growth – Acetic acid inhibits bacterial growth – Propionic acid retards molds – Lactic acid prevents anaerobic bacterial growth – Benzoic and sorbic acid inhibit yeast 11-88 © McGraw-Hill Education.  TABLE 11.13 Active Ingredients of Various Commercial Antimicrobial Products Product Specific Chemical Agent Antimicrobial Category Lysol and Clorox Sanitizing Wipes Dimethyl benzyl ammonium chloride Detergent (quat) Tilex and Lysol Mildew Remover Sodium hypochlorites Halogen Ajax and Dial Antibacterial Hand Triclosan Phenolic Soap Alkyl dimethyl benzyl Lysol Disinfecting Spray Detergent (quat)/alcohol ammonium/ethanol ReNu Contact Lens Solution Polyaminopropyl biguanide Chlorhexidine Wet Ones Antibacterial Moist Benzethonium chloride Detergent (quat) Towelettes Noxzema Triple Clean Triclosan Phenolic Scope Mouthwash Ethanol Alcohol Purell Instant Hand Sanitizer Ethanol Alcohol Pine-Sol Pine oil and surfactant Aldehydes, alcohols Allergan Eye Drops Sodium chlorite Halogen 11-89 © McGraw-Hill Education.