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104 Cards in this Set
- Front
- Back
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What are recontaminants?
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Microbes present at a give place and time that are undesirable or unwanted.
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What is the target of microbial control?
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Microorganisms capable of causing infection or spoilage that are constantly present in the external environment and the human body.
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What are the three different kinds of resistance?
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Highest, Moderate and Least resistance
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What are considered highest resistance?
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Prions: bacterial endospores, primarily bacteria in the genera Bacillus and Clostridium
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What are considered moderate resistance?
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Protozoan cyst; some fungal sexual spores (zygospores); some viruses. IN general, naked viruses are more resistant than enveloped forms.
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Give me an example of bacterias with an increased resistance of microbial control because of their vegetative cells.
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Mycobacterium - cell walls have thick, waxy layer that can block the entrance of disinfectants.
Pseudomonas, Acinobacter - outer membrane prevents penetration of chemical agents Staphylococcus species - heat resistant due to their thick, protective peptidoglycan cell walls |
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What are considered least resistant?
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Most bacterial vegetative cells; fungal spores (other than zygospores) and hyphae; enveloped viruses, yeasts; and protozoan trophozoites
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What is the goal of sterilization?
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Destroying microbial endospores
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What is disinfection?
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Destruction or removal of vegetative pathogens but not bacterial endospores, usually used only on inanimate objects.
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What is sterilization?
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complete removal or destruction of all viable microorganisms, used on inanimate objects.
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What is antisepsis?
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Chemicals applied to body surfaces to destroy or inhibit vegetative pathogens
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What is bactericide?
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chemical that destroys bacteria except for those in the endospore stage, it may or may not be effective on other microbial groups
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What is fungicide?
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chemical that can kill fungal spores, hyphae and yeast
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What is virucide?
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Any chemical know to inactivate viruses, especially on a living tissue
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What is sporicidal?
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Agent can destroy bacterial spores which makes it also a sterilizing agent
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What is microbial death?
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It is the permanet loss of reproductive capability, even under optimum grown conditions
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What are examples of mutagenic agents?
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Gamma, ultraviolet, or X radiation - causes mutations that result in permanent inactivation of DNA
Formaldehye and ethylene oxide - interfere with DNA and RNA function |
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What exhibit greatest and least resistant to both moist and dry heat?
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Bacterial endospores - greatest resistance
Vegetative states of bacteria and Fungi - least resistant |
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What is the reliable killing of most heat-resistant species of sporeformers?
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121 degrees C for 20 minutes of moist heat
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How we get Neisseria gonorrhea sensitive to heat?
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50 degrees C for 3 minutes
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How about staphylococcus aureus sensitivity to heat?
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60 degree C for 60 minutes
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What is the heat tolerance for Andenoviruses?
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55 degrees C for 2 to 5 minutes
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What is the heat tolerance for Hep A viruses?
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60 degrees C for 600 minutes
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How do we destroy all non-heat-resistant forms of bacteria, yeasts, molds, protozoa, worms and viruses?
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Exposure to 80 degrees C for 20 minutes
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What is thermal deat time (TDT)?
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The lowest temperature required to kill all microbes in a sample in 10 minutes.
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How do Clostridium botulinum for canneries get killed?
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Heat low-acid foods at 121 degrees C for 30 minutes, a treatment sterilizes these foods
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What are the common methods of Moist Heat Control
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Sterilization with Steam Under Pressure - Autoclave; Nonpressurized Steam - tyndallization; Boiling Water; Pasteurization
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What is the most efficient pressure-temperature combination for autoclave?
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15 psi, 121 degrees C
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When are nonpressurized steam used?
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Substances that cannot withstand high temperatues
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What is tyndallization?
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Intermittent sterilization. Requires a chamber to hold materials and a reservoir for boiling water. Items are exposed to free-flowing steam for 30 to 60 minutes. Items are incubated for 23 to 24 hours and is repeated 3 days in a row
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Why is it possible for a spore to germinate even after 3 days of tyndallization?
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Because temperature never gets above 100 degrees C
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What is boiling water used for ?
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Disenfection not sterilization because single processing at 100 degress C will not kill all resistant cells.
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How long do materials have to be exposed to boiling water?
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30 minutes. It will kill most non-spore forming pathogens, including resistant species such as tubercle bacillus and staphylococci
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What is pasteurization?
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Technique in which heat is applied to liquids to kill potential agents of infection and spoilage, while at the same time retaining the liquid flavor and food value.
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What is flash method?
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Pasteurization technique, exposes the liquid to heat exchangers at 71.6 degrees C for 15 seconds
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What is the greatest disadvantage of boiling water?
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Items can be recontaminated when removed from the water
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Why is flash method preferred over batch method?
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Because it less likely to change flavor and nutrient content, and it is more effective agaisnt resistant pathogens such as Coxiella and Myobacterium.
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What is batch method?
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Pasteurization technique, holds milk at 63 degrees to 66 degrees C for 30 minutes
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What is Thermoduric?
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Inactivate most virues and destroy the vegetative stages of 97% to 99% of bacteria, and fungi but do not kill endospores or microbes (mostly nonpathogenic)
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What are the nonpathogenic microbes that are not killed in pasteurization?
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Lactobacilli, micrococci, yeast
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What is the important aim of pasteurization?
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Prevent the transmission of milk-borne diseases form infected cows to milk handlers.
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How do sterile milk get processed?
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Ultrahigh temperature 134 degrees C for 2 to 5 seconds
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What are the primary target of pasteurization?
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Non-spore forming pathogens:
Salmonella species - common cause of food infection; Campylobacter jejuni - acute intestinal infection; Listerian monocytogenes - Listeriosis; Brucella species - undulant fever, Coxiella burnetii - Q fever, Mycobacterium bovis, M. tuberculosis |
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What is ionizing radiation?
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It sterilizes in the absence of heat, irradiation is a type of cold (low temperature) sterilization.
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What are different ionizing radiation penetration?
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Gamma rays - most penetrating, X-rays - intermediate; Cathod rays - least penetrating
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What are the desirable qualities of germicide?
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Rapid action in low concentration, solubility in water or alcohol and long-term stability, broad spectrum microbicidal action without being toxic to human and animal tissues; penetration of inanimate suraces to sustain a cumulative or persistent action; resistance to becoming inactivated by organic matter, noncorrosive or nonstaining properties, sanitizing and deodoring properties; affordability and ready availability; nonoffensive odor
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What are the two chemicals that fullfill the requirements for an ideal germicide?
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Chlordexidine and hydrogen peroxide
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What are three levels of chemical decontaminant procedures?
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High-level germicide, intermediate-level germicide and low levels of disinfection
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What are high-level germicide and its uses?
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Kill endospores, if properly used - sterilants. for Catheters, heart-lung equipment and implants - those are not heat sterilizable and are intended to enter the body tissues during medical procedures.
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What are intermediate-level germicide and its uses?
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Kill fungal (not bacterial) spores, resistant pathogents such as the tubercle bacillus and viruses. Disinfect items such respiratory equipment and thermometers that come in contact with mucous membrane but are noninvasive
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What are low levels of disinfection?
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Eliminate only vegetative bacteria, vegetative fungal cells, and some viruses
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What are the uses of low level disinfection?
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Used to clean materials such as electrodes, straps, and furnitures,that touch the skin surfaces but not the mucous membranes
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What is Phenol?
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Carbolic acid; is an acrid, poisonous compound derived from the distillation of coal tar.
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What is phenol coeffecient?
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Quantitatively compares a chemical's antimicrobiotic properties of those of phenol
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What are phenolics?
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Sustances chemically related to phenol
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What are the most important phenols?
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Alkylated phenols (cresols), chlorinated phenols, and bisphenols
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How do phenols work in high concentration?
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cellular poisons, rapidly disrupting cell walls and membranes and precipitating proteins
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How do phenols work in low concentration?
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Inactivate certain critical enzyme systems.
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What substances are destroyed by phenolics?
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Vegetative bacteria (including tuberculosis bacillus) fungi, and most viruses (not hepatitis B), but they are not reliably sporicidal.
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What are low levels of disinfection?
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Eliminate only vegetative bacteria, vegetative fungal cells, and some viruses
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What is a disadvantage of phenolics?
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Toxicity makes them dangerous to use as antiseptics
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What are the uses of low level disinfection?
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Used to clean materials such as electrodes, straps, and furnitures,that touch the skin surfaces but not the mucous membranes
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What is Phenol?
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Carbolic acid; is an acrid, poisonous compound derived from the distillation of coal tar.
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What is phenol coeffecient?
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Quantitatively compares a chemical's antimicrobiotic properties of those of phenol
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What are phenolics?
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Sustances chemically related to phenol
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What are the most important phenols?
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Alkylated phenols (cresols), chlorinated phenols, and bisphenols
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What are low levels of disinfection?
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Eliminate only vegetative bacteria, vegetative fungal cells, and some viruses
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How do phenols work in high concentration?
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cellular poisons, rapidly disrupting cell walls and membranes and precipitating proteins
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What are the uses of low level disinfection?
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Used to clean materials such as electrodes, straps, and furnitures,that touch the skin surfaces but not the mucous membranes
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How do phenols work in low concentration?
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Inactivate certain critical enzyme systems.
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What is Phenol?
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Carbolic acid; is an acrid, poisonous compound derived from the distillation of coal tar.
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What substances are destroyed by phenolics?
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Vegetative bacteria (including tuberculosis bacillus) fungi, and most viruses (not hepatitis B), but they are not reliably sporicidal.
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What is phenol coeffecient?
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Quantitatively compares a chemical's antimicrobiotic properties of those of phenol
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What is a disadvantage of phenolics?
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Toxicity makes them dangerous to use as antiseptics
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What are phenolics?
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Sustances chemically related to phenol
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What are the most important phenols?
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Alkylated phenols (cresols), chlorinated phenols, and bisphenols
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How do phenols work in high concentration?
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cellular poisons, rapidly disrupting cell walls and membranes and precipitating proteins
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How do phenols work in low concentration?
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Inactivate certain critical enzyme systems.
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What substances are destroyed by phenolics?
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Vegetative bacteria (including tuberculosis bacillus) fungi, and most viruses (not hepatitis B), but they are not reliably sporicidal.
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What is a disadvantage of phenolics?
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Toxicity makes them dangerous to use as antiseptics
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What are chlorhexidine?
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The compound chlorhexidine (hibiclens, hibitane) is a complex organic base containing chlorine and two phenolic rings
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What is the mode of action for chlorhexidine?
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Targets both cell membranes by lowering surface tension and protein structure by causing denaturation.
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What does chlorhexidine do in moderate and high concentrations?
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Bactericidal for both gram-positive and gram-negative bacteria but not against spores
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What are the advantages for chlorhexidine?
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Mildness, low toxicity, and rapid action, and it is not absorbed into deeper tissues to any extent.
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What is the antiseptic cleanser of choice to control Staphylococcus MRSA and Acinebacter outbreaks in hospitals?
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Chlorhexidine
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What types of alcohol are suitable for microbial control?
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Ethyl and isopropyl
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What do 50% and highger of alcohol concentration do?
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Dissolve membrane lipids, disrupt cell surface tension, and compromise membrane intergrity.
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How do alcohol denatures protoplasm?
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Through coagulation but only in alcohol-water solutions of 50 to 90 %
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Why do alcohol shows greater microbicidal activity at 70% concentration?
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because water is needed for protein to coagulate
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What happen in absolute alcohol (100%)?
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Alcohol dehydrate cells and inhibits their growth but is generally not a protein coagulant
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What is the use of alcohol?
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useful in intermediate to low-level disinfectants. Alcohol does not destroy bacterial spres at room temperature
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What do alcohol destroy provided time of exposure is adequate?
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resistant vegetative forms, including tuberculosis bacteria and fungal spores
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What do alcohol tend to inactivate?
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Enveloped viruses more readily than noneveloped viruses such as poliovirus and hepatitis A virus.
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What is hydrogen peroxide?
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Colorless caustic liquid that decomposes in the presence of light, metals or catalse into water and oxygen gas.
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What causes the germicidal effect of hydorgen peroxide?
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Direct and indirect actions of oxygen. Oxygen forms -OH free radicals, which like superoxide radical are highly toxic and reactive to cells.
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Why do microbial cells can't neutralize hydrogen peroxide even if it produces catalse to inactivate hydrogen peroxide?
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It cannot neutralize the amoutn of hydrogen peroxide entering the cell during disinfection and antisepsis.
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What are the uses of hydrogen peroxides?
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Endoscopes and dental handpieces
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What are two common aldehydes for micorbial control?
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Glutaraldehyde and formaldehyde
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What is glutaraldehyde?
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Yellow liquid with a mild odor
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What is glutaraldehyde mode of action?
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Cross-linking protein molecules on the cell surface. Amino acids are alkulated, meaning that a hydrogen atom on an amimno acid is replaced by the glutaraldehyde molecule itself. It can also irreversibly disrupt the activity of enzyme within cells.
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Why is glutaraldehyde considred as one of the few chemicals officically accepted as a sterilant and high-level disinfectant?
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Glutaraldehyde is a rapid and broad-spectrum. It kills spores in 3 hours and fungi and vegetative bacteria (even Mycobacterium and Pseudomonas) in few minutes.
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What is chemiclave?
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Similar to autoclave, vaporizes the solution under pressure to sterilize delicate instruments to heat.
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What are the disadvantages of gluataraldehyde?
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Retains potency even in the presence of organic matter, is noncorrosie, doesn't damage palstic ,and is less toxic or irritating than formaldehyde.
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What is the disadvantage of glutaraldehyde?
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Unstable especially with the increased pH and temperature.
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