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70 Cards in this Set
- Front
- Back
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Name the 3 general methods of microbial control
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Physical
Chemical Mechanical |
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Give examples of physical microbial control
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Physical agents include heat (both dry and moist) and radiation
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List and describe the mechanisms used in regard to dry heat
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Dry oven and incineration are both used for sterilization.
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What methods are used in regard to moist heat? What type of microbial control do they promote?
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Steam under pressure (sterilization)
Boiling water, and pasturization (disinfection) |
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Name the methods of radiation and the examples for each.
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Ionizing (x-ray, cathode, gamma)
Nonionizing (UV) |
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In regard to microbial control, give two examples of chemical agents.
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Gases and liquids
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Liquid agents can further be broken down into 3 methods of microbial control. What are they?
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Antisepsis
Disinfection Sterilization |
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What is Disinfection?
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The destruction or removal of vegetative pathogens but NOT bacterial endospores. It is used on inanimate objects (door handles, countertops, etc.)
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Define Sterilization.
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Sterilization is the complete removal or destruction of ALL viable microorganisms. It is used on inanimate objects (surgical tables, surgical tools, etc)
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What is the difference between disinfection and antisepsis?
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Antisepsis is the use of chemicals on body surfaces to destroy or inhibit vegetative pathogens (betadine in surgery, for example); disinfection is chemicals used only on inanimate objects.
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Name the 3 levels of resistance and give examples of each.
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HIGHEST--Prions
MODERATE--Protozoan cysts, some fungal sexual spores, some viruses LOWEST--bacterial vegetative cells, yeasts, protozoan trophozoites |
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Name the two most prominant genera that are found to be of highest resistance to microbial control.
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Bacillus and Clostridium (spores)
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What general category do all methods of microbial control belong to?
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Decontamination
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Name two methods of filtration (mechanical removal)
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Air (disinfection)
Liquid (sterilization) |
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What does "-cide" mean in context with words like fungicide, bactericide, virucide, and sporicidal?
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"-cide" means to kill. Therefore, a fungicide is any agent that can kill fungal spores, hyphae, and yeast; a sporicidal agent can kill endospores (sterilization); a bactericide is a chemical that destroys bacteria EXCEPT endospores.
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What is the distinguising difference between a bactericidal agent and a bacteriostatic agent?
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Bactericides destroy existing bacteria; bacteriostatic agents prevent the growth of new bacteria.
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What is another name for a germicide?
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Microbicide
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What types of materials can germicides be used on?
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Living tissue or inanimate materials, but does not kill resistant microbial cells.
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What is sepsis? Asepsis?
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Sepsis is the growth of microorganisms in blood or other tissues. Therefore, asepsis is the prevention of entry of infectious agents into sterile tissues (prevents infection)
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Give an example of a method of disinfection.
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Boiling water
5% bleach water |
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What is the difference between sanitization and sterilization?
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Sanitization removes microorganisms and debis from inannimate surfaces (ie: dishwashing); sterilization is the removal or destruction of all viable microbes (ie: autoclaving)
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What is the most accepted definition of microbial death?
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The permanent loss of reproductive capability, even under optimum growth conditions.
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How do surfactants work in regard to microbial control?
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Surfactants are chemicals that work because they lower the surface tension of cell membranes, opning the once-tight surface and leaving leaky areas that allow harmful chemicals into the cell and allow helpful ions to seep out.
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How do alcohols work?
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By dissolving membrane lipids and stripping membranes away from cells.
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What are 3 ways drugs affect infections?
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1. Block protein synthesis
2. Bind to DNA interferring with transcription and translation 3. Causing mutations (radiation) that inhibit DNA function |
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How does formaldehyde work?
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It interferes with DNA and RNA function.
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What is the most reliable temperature and length of time at which heat-resisitant species are killed?
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121 degrees C for 20 minutes in moist heat.
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How are non-heat-resistant forms of microbes destroyed?
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80 degrees C for 20 minutes.
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How can viruses be destroyed using heat?
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55 degrees C for 2-5 minutes (adenovirus)
Up to 60 degrees C for 600 minutes (hep A) |
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Give the moist heat range for bacteria and list two examples.
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50 degrees C for 3 minutes (Neisseria gonorrhoeae) to 60 degrees C for 60 minutes (S. aureus)
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What is Thermal Death Time (TDT)?
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TDT is the shortest length of time required to kill all test microbes at a specified temp.
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What is Thermal Death Point (TDP)?
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TDP is the lowest teimp required to kill all test microbes in a sample within 10 minutes.
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Commercial canneries heat low-acid foods at what temperature for what amount of time to sterilize?
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121 C for 30 minutes
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List for ways that moist heat is employed in microbial control
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1. steam under pressure
2. nonpressurized steam 3. boiling water 4 pasturization |
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What is normal atmoshperic pressure at sea level? At this pressure, at what temp will water boil?
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15 psi; 100 degrees Celsius
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How does pressurized steam kill microbes?
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By raising the steam's temperature.
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What is an autoclave?
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A device that can subject pure steam to pressures greater than 1 atm.
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What is the most efficient pressure-temp combination for sterilization in an autoclave? Average time?
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15 psi above normal (2 atm or 30psi) and 121 Celcius
20 minutes |
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What is tyndallization?
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Intermittent sterilization for substances that cannot withstand high temps of autoclaves. Cycle is repeated 3 days in a row, temp never goes above 100 Celsius.
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Explain the process of tyndallization.
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Items are put into a chamber that has a reservoir for boiling water and exposed to free-flowing steam for 30-60 minutes. It is assumed surviving spores will germinate, so materials are incubated at appropriate temps for 23-24 hours and then go through the process again. Cycle happens for 3 days in a row.
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What is pasturization? Give examples of materials it is used for.
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Heat is applied to liquids to kill potential agents of infection while retaining the flavor and food value.
Used for milk, fruit juices, etc. |
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Explain the flash method.
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A pasturization technique that exposes liquid to 71.5 degrees C for 15 seconds.
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What is the batch method and what is it generally used for?
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Holds liquids at 63-66 degrees C for 30 minutes. Used for milk.
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Is the batch or flash method preferred and why?
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The flash method; because it is less likely to alter the taste and nutrient content of food and more effective against certain resistant pathogens (Coxiella and Mycobacterium).
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Pasturization kills 97-99% of bacteria and fungi. What does it NOT kill?
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Endospores and thermoduric microbes
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At what temperature has sterile milk been treated?
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134 degrees C for 2-5 seconds
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What are the primary targets of pasturization?
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Campylobacter jejuni
Salmonella Brucella Coxiella burnetti Mycobacterium bovis M. tuberculosis |
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Incineration reaches temperatures of _____________.
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800-6500 degrees Celcius
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Dry ovens range in heat and time from __________to_________.
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150-180 degrees Celcius
12 minutes to 4 hours |
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What is lyophilization?
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A treatment that combines freezing and drying--materials are frozen quickly, and exposed to a vacuum that removes all water.
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What are the two consequences of radiation?
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1. Radiation ejects orbital electrons from an atom and causes ions to form (ionizing radiation)
2. Exciting atoms by raising them to a high energy level--leads to the formation of abnormal bonds (mutation, nonionizing) |
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What is the unit measurement for ionizing radiation?
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Grays (used to be rads)
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Exposure of ionizing radiation ranges from ____ to _____ (give measurement label as well).
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5 to 50 kilograys
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List the 3 types of ionizing rays in order from most penetrating to least penetrating.
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Gamma
X-rays Cathode |
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List some desirable qualities of germicides .
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--rapid action in low concentration
--solubility and long-term stability --broad-spectrum action (nontoxic to human/animals) --penetration of inanimate surfaces --resistance of inactivation --sanitizing/deodorizing --affordability, availability --nonoffensive odor |
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What two chemicals come close to approaching the ideal requirements for microbial control?
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Hydrogen peroxide
Chlorhexidine |
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List 3 levels of chemical decontamination and give examples of what each of them kills.
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HIGH--kills endospores; if properly used they are considered sterilants (used on medical equipment.
INTERMEDIATE--kill fungal (NOT bacterial) spores, resistant pathogens, and viruses (used on respiratory equipment, thermometers--anything coming into intimate contact with mucous membranes) LOW--kill only vegetative bacteria, vegetative fungal cells, and some viruses (used on electrodes, straps, and furniture). |
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How is phenol derived?
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From the distillation of coal tar
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What is the phenol coefficient?
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The quatitative comparison of a chemical's antimicrobic properties to that of phenol.
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What is the molecular structure of phenolics?
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Phenolics have one or more aromatic carbon rings with added functional groups.
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What are the most important phenols?
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Alkylated phenols
Chlorinated phenols Bisphenols |
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What is the mechanism of action of a phenol?
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HIGH concentration--Disruption of cells walls and membrans and preciptating proteins
LOW concentration--inactivation of critical enzyme systems |
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Why are phenolics NOT used as antiseptics?
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The level of toxicity is too dangerous
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Describe Chlorhexidine and give an example.
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Complex organic base containing chlorine and 2 phonolic rings; Hibiclens and Hibitane)
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Describe alcohols as antimicrobial agents and give examples.
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Alcohols are colorless hydrobarbons with one or more -OH functional groups; (ethyl and isopropyl)
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What is the mechanism of action of alcohol?
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Depends on its concenration
50%+ dissolve membrane lipids, and compromise membrane integrity 70% (30% water) has greater microbial activity than 100% because H20 is needed for protein coagulation. 100% dehydrates cells and inhibits growth but is not a protein coagulant. |
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Of enveloped and nonenveloped viruses, which does alcohol act more efficiently on?
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Works more readily on enveloped viruses
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What factors affect the efficiency of germicides?
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Time of exposure
Concentration of chemicals |
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List in order the temperatures and exposure times for the following methods of pasturization:
1. flash method 2. batch method 3. sterile milk |
1. 71.6 degrees Celius for 15 seconds
2. 63-66 degrees Celcius for 30-60 minutes 3. 134 degrees Celcius for 2-5 seconds |
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What is the disadvantage of disinfection with boiling water?
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Materials can become recontaminated once removed from the water.
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