Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Micro Ch.11 Control
Microbial control - ch. 11
| Question | Answer |
|---|---|
| Sterilization | destruction of all microbial life |
| Disinfection | destroys most microbial life, reducing contamination on inanimate surfaces |
| Antisepsis | same as disinfection except a living surface is involved |
| Decontamination | mechanical removal of most microbes from an animate or inanimate surface |
| Highest relative resistance of microbial forms | Highest |
| Moderate relative resistance of microbial forms | Protozoan cysts, sexual fungal spores, naked viruses, Mycobacterium |
| Least relative resistance of microbial forms | Most bacterial vegetative cells, ordinary fungal spores, enveloped viruses, yeasts, and protozoan trophozoites |
| Sterilization | process that destroys/removes all viable microorganisms, including viruses |
| Sterile | any material that has been subjected to sterilization |
| Sterilants | chemicals that can be classifired as sterilizing agents because of their ability to destroy spores. |
| Disinfection | use of a physical process or a chemical agent (disinfectant) to destroy vegetative pathogens but not bacterial endospores; normally used on inanimate objects b/c can be toxic to animal/human tissue; also remove toxins |
| Sepsis | growth of microorganisms in the blood and other tissues |
| Asepsis | any practice that prevents entry of infectious agents into sterile tissues and prevents infection. |
| Antiseptics | chemical agents directly exposed to body surfaces, wounds, surgical incisions to destroy or inhibit vegetative pathogens (ex. iodine) |
| –cide | “to kill” |
| Bactericide | chemical that destroys bacteria except for those in the endospore stage; may or may not be effective on other microbial groups |
| Germicide | kills germs |
| Fungicide | kills fungal spores, hypae, and yeasts |
| Virucide | chemical known to inactivate viruses, especially on living tissue |
| –static | “stand still;” microbes temporarily prevented from multiplying but are not killed outright. |
| Bacteristatic | prevent growth of bacteria on tissues/objects |
| Microbistatic | used to control microorganisms in the body (antiseptics and drugs); many compounds can be toxic to human cells. |
| Decontamination | reducing levels of microorganisms |
| Sanitization | any cleansing technique that mechanically removes microorganisms/other debris to reduce contamination to safe levels (ex. soap, detergent) |
| Degermation | reduce number of microbes on human skin; usually involves scrubbing, immersion in chemicals, or both. Also emulsifies oils and mechanically removes potential pathogens on the outer layers of the skin. i.e. handwashing, alchohol swabs |
| Practical concerns in microbial control | require sterilization, or disinfection adequate? spores? item to be reused/discarded? item withstand heat, pressure, radiation, chemicals? Will agent penetrate to necessary extent? Is method cost/labor efficient and safe? |
| What is microbial death? | Phenomenon that involves the permanent termination of an organism’s vital processes. Permanent loss of reproductive capability—even under optimal conditions—has become accepted microbiological definition of death. |
| Factors that affect death rate | numbers, nature of microorganism, temperature, pH, concentration of agent, MOA of agent, Presence of solvents, organic matter, and inhibitors (i.e. saliva, blood, feces) |
| How antimicrobial agents work | Their modes of action. Agents affect one or more cellular targets, inflicting damage progressively until the cell is no longer able to survive. |
| The effects of agents on the cell wall | Cells deprived of functional cell wall lyse easily |
| How agents affect the cell membrane | if disrupted, loses selective permeability, leading to cell death |
| Surfactants (detergents) | lower surface tension of cell membranes; physically bind to lipid layer of membrane and penetrate internal hydrophobic region. Opens up usually tight interface, making leaky spots that lead to bad chemicals seeping in and good chemicals seeping out. |
| Agents that affect protein and nucleic acid synthesis | microbial life depends on orderly and continuous supply of proteins to function as enzymes and structural molecules. |
| Ribosome function | antibiotic can stop peptide formation, preventing ribosome from synthesizing proteins required in growth/metabolism |
| DNA and RNA function | preventional of transcription/translation |
| Methods of Physical Control | heat, |
| Moist heat | occurs in form of hot water, boiling water, or steam. Temp of moist heat usually ranges from 60oC to 135°C. Operates at lower temperatures and shorter exposure times to achieve the same effectiveness as dry heat. |
| Dry heat | denotes air with a low moisture content that has been heated by a flame or electric heating coil; ranges from 60°C to several thousand degrees Celsius. |
| MOA of heat | Most microbicidal effect is coagulation and denaturation of proteins, which quickly and permanently halts cellular metabolism |
| MOA of heat | Dehydrates the cell—removes water necessary for metabolic reactions; Denatures proteins; Some proteins prefer dehydrated conditions, so high heat is necessary for microbial control—burning to ashes |
| Heat resistance | Endospores have greatest resistance; Vegetative states of bacteria/fungi are least resistant to both moist and dry heat |
| Practical concerns in the use of heat | Thermal death measurements—as a general rule, higher temperatures allow shorter exposure times and lower temperatures require longer exposure times. |
| Thermal death time | TDT—defined as the shortest length of time required to kill all test microbes at a specified temperature |
| Thermal death point | TDP—defined as the lowest temperature required to kill all microbes in a sample in 10 minutes |
| Common methods of moist heat control | steam under pressure, autoclave, tyndallization, pasteurization |
| Steam under pressure | to raise temperature of steam, pressure under which it is generated is increased. Increase in pressure = temperature at which water boils and steam produced rise. |
| Autoclave | chamber with airtight door, Sterilization is achieved when the steam condenses against the objects in the chamber and gradually raises their temperature. Ineffective for sterilizing substances that repel moisture (oils, waxes, powders) |
| Nonpressurized steam | for substances that cannot withstand high temperature of autoclave. |
| Tyndallization | (intermittent sterilization) Items exposed to free-flowing steam intermittenly; temp not sufficient to kill spores, so Cycle repeated for 3 days in a row. B/c temperature does not exceed 100°C, highly resistant spores that do not germinate may survive. |
| Pasteurization | Disinfection of beverages; technique in which heat is applied to liquids to kill potential agents of infection/spoilage, while retaining liquid’s flavor and food value. |
| Boiling water | Disinfection; boiling water bath/chamber can quickly decontaminate items; can be relied on only for disinfection—not sterilization; boiling for 30min will kill most non-sporeforming pathogens. Disadvantage—items easily recontaminated. |
| Dry heat | Hot air and incineration |
| Cold decontamination | retards activities of microbes; only slows down growth, does not stop it. |
| Dessication | vegetative cells directly exposed to normal room air gradually become dehydrated or dessicated |
| Lyophilization | combination of freezing and drying; common method of preserving microorganisms and other cells in a viable state for many years. |
| Radiation | energy emitted form atomic activities and dispersed at high velocity through matter or space; gamma rays, X rays, ultraviolet radiation |
| Effects of radiation on microbes | irradiation, or bombardment with radiation at the cellular level. a cell bombarded w/ certain waves or particles, its molecules absorb some of the available energy leading to one of two consequences |
| Non-ionizing radiation | excites atoms by raising them to a higher energy state, but does not ionize them. Low energy. |
| Ionizing radiation | Gamma rays, X rays, and cathode rays; radiation ejects orbital electrons from atom, causes ions to form. Seen in gamma rays, xrays, high-speed electrons. High energy; penetrates liquids and solids effectively |
| Ionizing radiation | highly effective alternative for sterilizing materials that are sensitive to heat/chemicals; Considered a cold sterilization |
| Applications of ionizing radiation | items placed in machines and irradiated for a short time with a carefully chosen dosage; gamma rays are most penetrating, x rays are intermediate, and cathode rays are least penetrating. |
| Non-ionizing radiation | Source of UV radiation is germicidal lamp; Lower energy so not as penetrating as ionizing radiation; Causes specific molecular damage to pyrimidine bases, which form abnormal linkages with each other called pyrimidine dimers. |
| Applications of ultraviolet radiation | powerful took for destroying fungal cells/spores, bacterial vegetative cells, protozoa, and viruses; Directed at disinfection rather than sterilization |
| Disadvantages of UV radiation | poor power of penetration through solid materials (glass, metal, cloth, plastic, paper); damaging effect of UV overexposure on human tissues, including sunburn, retinal damage, cancer, skin wrinkling. |
| Decontamination by filtration | An effective method to remove microbes from air and liquids. |
| Applications of filtration | to prepare liquids that cannot withstand heat (serum, blood products, vaccines, drugs, IV fluids, enzymes, media). Alternative method for decontamination of milk and beer, water purification. Efficiently removes airborne contaminates (HEPA filters) |
| Disadvantage of Decontamination by filtration | does not remove soluble molecules (toxins) that can cause disease |
| Antimicrobial elements | can occur in liquid, gaseous, or solid state and they range from disinfectants, antibiotics, sterilants, preservatives. |
| Antimicrobial elements | Many are dissolved into water, alcohol, or mixture of both into a liquid solution (convenience) |
| Aqueous antimicrobial solutions | Solutions with pure water as solvent |
| Tinctures | antimicrobial Solutions with solvent of pure alcohol/water-alcohol mixture |
| Germicide desireable qualities | Rapid action, Solubitily in water/alcohol; Broad-spectrum micrbidical action without being toxic to human/animal tissues; Penetration of inanimate surfaces to sustain cumulative/persistant action; Affordability, ready availability |
| High-level germicides | kill endospores and are sterilants if used correctly; used on medical devices that are not heat-sterilizable |
| Intermediate-level germicides | kill fungal (but not bacterial) spores, resistant pathogens, and viruses. Used to disinfect items that come into intimate contact w/ mucous membranes but are noninvasive. |
| Low-level germicides | eliminate only vegetative bacteria, vegetative fungal cells, some viruses. Used to clean electrodes, straps, pieces of furniture that touch skin but not mucous membrane. |
| Factors that affect the germicidal activity of chemicals | Nature of microorganism, Nature of material being treated, Degree of contamination, Time of exposure, Strength and chemical action of germicide |
| The halogen antimicrobial chemicals | fluorine, bromine, chlorine, iodine (nonmetallic elements). Highly effective components of disinfectants and antiseptics because they are microbicidal and not just micrbistatic, plus sporicidal with longer exposure. |
| Chlorine | Disrupt sulfhydryl groups in amino acids; Major forms used in microbial control are liquid and gaseous chlorine, hypochlorites, chloramines |
| Chlorine compounds in disinfection and antisepsis | gaseous/liquid chlorine used almost exclusively for large-scale disinfection of drinking water, sewage, wastewater |
| Hypochlorites | most extensively used; used for sanitization/disinfection of food equipment, treatment of swimming pools, to treat wounds/disinfect equipment/bedding/instruments. |
| Chloramines | alternative to pure chlorine in treating water supplies |
| Iodine and its compounds | Iodine rapidly penetrates cells, disturbs variety of metabolic functions by interfereing w/ hydrogen and disulfide bonding of proteins. Will kills all classes of microorganisms if used properly. |
| Free iodine | iodine preparation; in solution. |
| Iodophors (alcohol and iodine complex) | allows slow release of free iodine, increases degree of penetration. Less prone to irritate tissue |
| Applications of iodine solutions | topical antiseptic before surgery; treatment for burned/infected skin; stronger solution can be disinfectant for plastic/rubber items, blades, thermometers. |
| Iodine tincture | used in skin antisepsis; not routine since can be harsh |
| Phenol and its derivatives | phenol (carbolic acid) |
| Phenol coefficient | compares a chemical’s antimicrobic properties to those of phenol. |
| Phenolics | substances chemically related to phenol; consist of one or more carbon rings with added functional groups. Strongly microbicidal, Toxic, |
| Applications of phenolics | general disinfection of drains, cesspools, animal quarters; seldom used as medical germicide. |
| Triclosan | antibacterial compound added to products like soaps, kitty litter; broad-spectrum in its effects. |
| Chlorhexidine | MOA targets both cell membranes—lowering surface tension until selective permeability is lost—and protein structure, causing denaturation. Surgical hand scrub, Obstetric antiseptic |
| Alcohols as antimicrobial agents | Ethyl alcohol, isopropyl (rubber alcohol) |
| Alcohol antimicrobial MOA | 70% concentration dissolve membrane lipids, disrupt cell surface tension, denatures proteins |
| Applications of alcohols | Germicidal and skin degerming; nonirritating, inexpensive |
| Hydrogen peroxide and related germicides | Colorless and caustic liquid; Form hydroxyl free radicals; Effective against anaerobes; Skin and wound cleaner; Quick method for sterilizing medical equipment |
| Chemicals with surface action | Detergents |
| Quaternary ammonium (quats) | Cationic, Bind and disrupt cell membrane, Low-level disinfectant in the clinical setting |
| Anionic detergents (negatively charged) | limited microbicidal power |
| Cationic detergents (positively charged) | much more effective |
| Heavy metal compounds | Mercury, silver; Inactivate proteins |
| Oligodynamic action | property of having antimicrobial effects in exceedingly small amounts. |
| Heavy metal compounds Drawbacks | Toxic to humans; Allergic reactions; Neutralized by biological fluids and wastes; Resistance can develop in treated microbes; Applications of heavy metals; Preservatives in cosmetics and ophthalmic solutions |
| Aldehydes as germicides | Organic substances bearing a –CHO functional group on the terminal carbon; Two most commonly used |
| Glutaraldehyde | MOA involves cross-linking protein molecules on the cell surface; amino acids are alkylated, meaning that a hydrogen atom on an amino acid is replaced by the glutaraldehyde molecule itself. Also irreversibly disrupts enzyme activity in the cell. |
| Applications of the aldehydes | disinfectant of surgical instruments; milder chemical for sterilizing materials damaged by heat; preservation of vaccines, degerm cow teats. |
| Gaseous sterilants and disinfectants | versatile alternative to heat or liquid chemicals |
| Ethylene oxide | colorless, exists as gas at room temperature. Very explosive in air, so mixed with CO2 or fluorocarbon; Reacts with functional groups of DNA and proteins |
| Applications of gases and aerosols | Sterilizes and disinfects plastic materials |
| Dyes as antimicrobial agents | Crystal violet and malachite green; very active against gram-positive species of bacteria and various fungi, so incorporated into solutions and ointments to treat skin infections (i.e. ringworm). |
| Acridine dyes | yellow; used for antisepsis and wound treatment |
| Acids and alkalis | acetic acid; Ammonium hydroxide; Prevents spore germination and vegetative growth. Food preservative |
| Germicidal | agent lethal to non-endospore-forming pathogens; Root cide—to kill |
| Bacteriostatic | agent/process that prevents growth of bacteria on tissues/objects. Root static—stand still |
| Antiseptic | chemical agents directly exposed to body surfaces, wounds, and surgical incisions to destroy or inhibit vegetative pathogens (ex. iodine). Root septic—infection |
| Thermal death time | TDT—defined as the shortest length of time required to kill all test microbes at a specified temperature |
| Thermal death point | TDP—defined as the lowest temperature required to kill all microbes in a sample in 10 minutes |
| You are working in primitive conditions and have only a campfire and pot. You have water and a watch but no thermometer. How would you make the water safe to drink? | Boiling the water for at least 30 minutes will kill most non-sporeforming pathogens. |
| Using the same equipment how would you sterilize tools for an emergency field surgery? | By “flaming” the tools with the fire (akin to flaming our loops in lab) |
| You must kill bacterial spores. How could you do so? List all methods. | Sterilization via Tendyllization, autoclave, incineration, ethylene oxide, gluteraldehyde |
| I have been making beer at home. How can I stop the fermentation process? List 2 methods. | Expose it to oxygen; lower the temperature |
| How is milk made safe to drink? | Pasteurization |
| I have a bag of medical waste. Provide some recommendations on getting rid of it in a safe way. | Incineration |
| Describe the effects of ionizing radiation on DNA. Why is this an effective means of sterilization? | Ionizing radiation causes molecules to become excited—ejects orbital electrons from an atom and causes ions to form. This means it could break bonds—like the bonds found in DNA which, if broken, would affect cellular processes. |
| How are heavy metals used in the pharmaceutical industry? | They are used as preservatives in cosmetics and ophthalmic solutions. |
| How are iodophors used? | As antiseptic and disinfectant to prepare skin/equipment for surgery/injections, surgical hand scrubbing, burn treatment |
| Describe the uses of phenolics. List a common phenolic that is no longer used and tell me why not? | Phenolics are found in products used for general disinfection of drains, cesspools, animal quarters, and in kitty litter and soaps. Phenol was the major antimicrobial chemical until less harmful/toxic phenolics were developed. |
| What is a “quat”? How might it be used? | Quaternary ammonium; is considered a detergent and is used as a low-level disinfectant in the clinical setting. |
| What disinfectant do we use in the lab? Why is a good or bad choice? | We use Lysol in the lab to clean our workspace. It is a phenolic disinfectant and is a good choice since phenols are strongly microbicidal and will destroy vegetative bacteria, fungi, and most viruses. |
Created by:
mbtrimm
Popular Biology sets