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58 Cards in this Set
- Front
- Back
What is sterilization?
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Destruction or removal of all forms of microbial life, including endospores. (p.188)
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What is commercial sterilization?
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Sufficient heat treatment to kill endospores of Clostridium botulinum in canned food.
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Define disinfection-
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Destruction of vegetative pathogens. p.188
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Define antisepsis
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Destruction of vegetative pathogens on living tissue. p.188
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Define degerming
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Removal of microbes from a limited area, such as the skin around the injection site. p.188
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Define sanitization
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Treatment intended to lower microbial counts on eating and drinking utensils to safe public health levels. p.188
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Why is sterilization so difficult to achieve?
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Because sterilization is the removal or destruction of ALL forms of microbial life. p.188
(keep in mind that a bacterial death or decline phase is logarithmic, and that survivors turn on the expression of genes whose products make them very difficult to kill.) |
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What are some enviornmental factors that will affect the rate of microbial death?
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The presence of organic matter often inhibits the action of chemical antimicrobials.
(Ex: In hospitals the presence of organic matter in blood, vomit, or feces influences the selection of disinfectants.) p.190 |
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What is biocide or germicide?
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kills microorganisms (usually with certain exceptions, such as endospores) p.189
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What does bacteriostasis mean?
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Treatment that only inhibits the growth and multiplication of bacteria. Once bacteriostatic agent is removed, growth might resume. p.189
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What does sepsis mean?
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From the Greek for decay or putrid, indicates bacterial contamination as in septic tanks for sewage treatment. p.189
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What does asepsis mean?
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the absence of significant contamination. p.189
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What are some factors that influence the effectiveness of antimicrobial treatments?
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1) The number of microbes.
2) Environmental influences. (presence of organic matter) 3) Time exposure (often req. extended amt. of exposure for more resistant microbes or endospores to be affected.) 4) Microbial characteristics p.189-190 |
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What cellular structures are the targets of various microbial control agents?
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A microorganism's plasma membrane, located just inside the cell wall.
Damage to the lipids or proteins of the plasma membrane by antimicrobial agents cause cellular contents to leak into the surrounding medium and interferes w/ the growth of the cell. p.190 |
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What are some physical methods for controlling microbial growth to preserve foods, used in the Stone Age?
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1) Desiccation (drying)
2) Osmotic pressure (salting) p.190 |
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How can heat be used to sterilize objects?
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Heat appears to kill microorganisms by denaturing their enzymes; the resultant changes to the 3-dimensional shapes of these proteins inactivate them. p.191
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What factors determine what application of heat will be used?
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1) Heat resistance. Thermal death point (TDP) is the lowest temp. at which all the microorganisms in a particular liquid suspension will be killed in 10 mins.
2) Length of time required. Thermal death time (TDT), the min. length of time for all bacteria in a particular liquid culture to be killed at a given temperature. 3) Decimal reduction time (DRT or D value): time in minutes in which 90% of population of bacteria at a given temp. will be killed. p.191 |
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Both refrigeration and pasteurization are used to control microbial growth in food. Are these strategies bacteriostatic or bacteriocidal?
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These strategies are bacteriostatic.
They lower microbial numbers which prolongs milks good quality under refrigeration. p.193 |
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How does moist heat kill microorganisms?
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Primarily by the coagulation of proteins (denaturation), which is caused by breakage of the hydrogen bonds that hold the proteins in their three-dimensional structure.
(ex: watch an egg white frying) p.191 |
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Is boiling always a reliable sterilization procedure?
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No. Some endospores and viruses are not destroyed w/in 10 mins. of boiling.
Some Hepititis viruses can survive 30 mins. of boiling, & some bacterial endospores can resist boiling for more than 20 hrs. HOWEVER, brief boiling at high altitudes, will kill most pathogens. (Ex: boiling to sanitize baby bottles) p.191 |
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What is a reliable sterilization procedure using moist heat?
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In autoclaving high temperatures above boiling temperatures are achieved by steam under pressure in an autoclave.
This method is preferred unless the material to be sterilized can be damaged by heat or moisture. p.191 |
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The higher the -----in the autoclave, the higher the----.
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pressure
temperature. p.192 |
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Autoclaving is used to sterilize...
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culture media, instruments, dressings, intravenous equipment, applicators, solutions, syringes, transfusion equipment and numerous other items that can withstand high temperatures and pressures.
p.192 |
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Heating is less efficient in foods that are more -----, and ----in food can have a protective effect on microorganisms.
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viscous
fats p.193 |
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Milk pasteurization today uses high temperatures 72 degrees celsius for only 15 seconds. This treatment is known as...
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High-temperature short-time (HTST) pasteurization, is applied as the milk flows continuously past a heat exchanger. Kills pathogens and lowers total bacterial counts, so the milk keeps well under refrigeration.
p.193 |
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What is the cellular target of Moist heat: boiling or flowing steam?
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mechanism of action:
protein denaturation Kills vegetative bacterial & fungal pathogens & almost all viruses w/in 10 mins.; less effective on endospores. p.197 |
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What is the cellular target of Moist heat: Autoclaving?
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mechanism of action:
Protein denaturation Very effective method of sterilization; at about 15psi of pressure (121 degrees Celsius), ALL vegetative cells & their endospores are killed in about 15 mins. Preferred use: Microbiological media: solutions, linens, utensils, dressings, equipment, & other items that can withstand temperature and pressure. p.197 |
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What is the cellular target of Moist heat: Pasteurization?
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mechanism of action:
Protein denaturation. Heat treatment for milk (72 degrees Celsius for about 15 secs.) that kills ALL pathogens and MOST nonpathogens. Preferred use: Milk, cream, & certain alcoholic beverages (beer and wine) |
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What is the cellular target for Dry Heat: Direct Flaming?
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mechanism of action:
Burning contaminants to ashes. Very effective method of sterilization. Preferred use: Inoculating loops. p.197 |
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What is the cellular target for Dry Heat: Incineration?
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mechanism of action:
Burning to ashes. Very effective method of sterilization. Preferred use: paper cups, contaminated dressings, animal carcasses, bags and wipes. p.197 |
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What is the cellular target for Dry Heat: Hot-air sterilization?
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mechanism of action:
oxidation. Very effective method of sterilization but reqs. temperature of 170 degrees Celsius for about 2 hrs. Preferred use: Empty glassware, instruments, needles, and glass syringes. p.197 |
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How does Filtration work?
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mechanism of action:
Separation of bacteria from suspending liquid. Removes microbes by passage of a liquid or gas through a screen like material. Most filters in use consist of cellulose acetate or nitrocellulose. Preferred use: sterilizing liquids (enzymes, vaccines) that are destroyed by heat. p.197 |
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What is the cellular target of Cold: Refrigeration?
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mechanism of action:
decreased chemical reactions & possible changes in proteins. Has BACTERIOSTATIC effect. Preferred use: food, drug, and culture preservation. p.197 |
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What is the cellular target of Cold: Deep Freezing?
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mechanism of action:
decreased chemical reactions and possible changes in proteins. An effective method for preserving microbial cultures, in which cultures are quick-frozen between -50 degrees Celsius and -95 degrees Celsius. Preferred use: Food, drug, and culture preservation. p.197 |
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What is the cellular target of Cold: Lyophilization?
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mechanism of action:
Decreased chemical reactions and possible changes in proteins. Most effective method for LONGterm Preservation of microbial cultures; water removed by high vaccum at low temperature. Preferred use: Food, drug, and culture preservation. p.197 |
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What is the cellular target of High Pressure?
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mechanism of action:
Alteration of molecular structure of proteins and carbohydrates. Preservation of colors, flavors and nutrient values. Preferred use: Fruit juices. p.197 |
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What is the cellular target of Desiccation?
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mechanism of action:
Disruption of metabolism. Involves removing water from microbes; PRIMARILY BACTERIOSTATIC. Preferred use: Food preservation. p.197 |
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What is the cellular target for Osmotic Pressure?
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mechanism of action:
Plasmolysis. Results in loss of water from microbial cells. Preferred use: Food preservation. p.197 |
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What is the cellular target of Radiation: Ionizing?
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mechanism of action:
Destruction of DNA. Not widespread in routine sterilization. Preferred use: sterilizing pharmaceuticals and medical and dental supplies. p.197 |
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What is the cellular target of Radiation: Nonionzing?
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mechanism of action:
Damage to DNA. Radiation is NOT very penetrating. (organisms to be killed must be directly exposed to rays.p.196) Preferred use: Control of closed environment w/ UV (germicidal) lamp. p.197 |
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How does filtration work? Does this method of microbial control kill microorganisms?
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Passage of a liquid or gas through a a screenlike material w/ pores small enough to retain microorganisms. A vacuum is created in the receiving flask; air pressure then forces the liquid through the filter. p.194
No. |
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Radiation that kills microorganisms (sterilizing radiation) is of two types:
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ionizing and nonionizing. p.195
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Gamma rays, X-rays or high energy beams are forms of...
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Ionizing radiation. Has a shorter wavelength than that of nonionizing radiation, less than about 1nm. Carries More energy.
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What is the cellular target of Nonionizing radiation?
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UV light damages DNA of exposed cells by causing bonds to form between adjacent pyrimidine bases, usually thymines, in DNA chains.
Thymine dimers inhibit correct replication of the DNA during reproduction of the cell. p.196 |
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What is a major disadvantage of UV light as a disinfectant?
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It is not very penetrating, so the organisms to be killed must be directly exposed to the rays.
side note: prolonged exposure can cause burns and skin cancer in humans. p.196 |
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How can the effectiveness of a disinfectant be determined?
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By the number of cultures that grow. p.198
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Lister was the first to use-----to control surgical infections in the operating room.
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phenol (carbolic acid)
Now, rarely used as an antiseptic or disinfectant b/c it irritates the skin and has a disagreeable odor. p.198 |
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Soaps and detergents are examples of--------
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surfactants: surface-active agents.
important function in the Mechanical removal of microbes through scrubbing. p.202 |
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What are quats?
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Quaternary ammonium compounds.
they are modifications of the four valence ammonium ion. Strongly Bacteriocidal against gram (+) bacteria, less active against gram (-) bacteria. Also fungicidal, amoebicidal, & virucidal against enveloped viruses. They change the cell's permeability & cause the loss of essential cytoplasmic constituents, such as potassium. p.202-203 |
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What are the major drawbacks of using ethylene oxide and beta-propiolactone?
When would they be used? |
They are suspected carcinogens. p.205
Used on medical supplies and equipment. Ex: ethylene oxide chambers, large enough to sterilize mattresses. |
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Why are antibiotics not included in this chapter?
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The compounds discussed in this chapter are NOT generally useful in the treatment of diseases.
Because antibiotics are used in chemotherapy, antibiotics and the pathogens against which they are active will be discussed in Ch. 20. p. 207 |
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What is the best method for sterilization of an enzyme solution?
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Filtration.
(Micro CD) |
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Some antimicrobial treatments kill microbes; some inhibit growth. Which term refers to an agent that inhibits bacterial growth?
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Bacteriostatic
(Micro CD) |
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Pasteurization was first used by Pasteur to control spoilage of....
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Wine.
(Micro CD) |
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Packages of milk and coffee creamers may be stored w/out refrigeration if they have been sterilized by...
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Ultra high temperature treatment (UHT)
(Micro CD) |
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The 1st disinfectant used by Lister was...
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phenol.
(Micro CD) |
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Alcohol is most effective when used as a --------- solution.
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70%
(Micro CD) |
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----------- is a compound found in antimicrobial soaps that target gram-positive bacteria.
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Triclosan.
(p.200) |