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133 Cards in this Set
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standard plate count
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one method that is commonly used to determine the number of bacteria in milk, various foods and water.
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the safety of a food product
the course of infection the effectiveness of an antibiotic or disinfectant deciding whether a beach should be closed or not due to fecal contamination |
What are some ways that being able to enumerate (count) the number of bacteria in a sample can be crucial to help in determination?
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Because the numbers in original bacteria sample are too high to count, so they must be diluted to put in the formula to get the orginal sample number.
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Why are samples of bacteria diluted?
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colony forming units (CFU)
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btwn 30-300 growing in or on the plate.
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The # of CFU (30-300) X the dilution factor (the reciprocal of the dilution) = # CFU/g of soil.
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What is the formula used to estimate the number of bacteria in the original sample?
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aerobic and facultative bacteria
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What types of bacteria can grow under these diluted conditions?
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Dilution
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1/5 or 1:5 means 1 part in 5 parts total. To make a 1:30 dilution add 1mL sample to 29 mL diluent.
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titer
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the highest dilution showing a + reaction
sero + = A + rxn |
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blanks
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sterile tubes or bottles containing measured amounts of sterile water.
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bacteriostatic
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Substances or conditions that kill bacteria without killing them
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bactericidal
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Substances or conditions that kill bacteria
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fungicide
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lethal to fungi
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virucide
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kill inactive viruses
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sporicidal agent
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kill spores
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germicide
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activity against a wide range of microorganisms.
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Sterilization
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destruction of all life forms of life. There is no life present in it or on it.
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disinfection
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The destruction of vegetative pathogens. Substance still contain living microbes.
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antibiotic
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Controlling microbial growth doesn't just involve killing or inhibiting them, it involves using microbes to produce an _________, growing genetically engineered microbes to produce a pharmaceutical product, or using them for food production, controlling microbial growth involves keeping them alive and even enhancing their growth.
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sepsis
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presence of microbes in the blood.
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binary fission
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bacterial cells reproduce by an asexual process called _________ _________.
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binary fission
daughter cell |
the cell replicates its chromosomes (DNA) and them forms a septum that divides the cell into two _________ _____ each containing a complete chromosome.
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generation time
doubling time |
The amount of time it takes for a cell to replicate itself is termed the ___________ _____ or ___________ _____.
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Direct flame
Incineration Hot air sterilization |
What are the 3 dry heat methods of killing microorganisms?
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Direct flame
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100% sterilization
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Incineration
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burning to ashes
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Hot air sterilization
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Drying oven (glass ware & instrument needles)
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Moist heat method
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kills by denaturing proteins.
Boiling in water (e.g.) |
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Boiling in water
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15-30
kills most vegetative cells, but not endospores. |
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growth curve
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When bacteria are introduced into a new environment they tend to follow a typical pattern called the ________ ________.
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Lag phase
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At this stage there is little or no replication. Bacteria at this stage are adjusting to their new environment and synthesizing enzymes to utilize nutrients in the environment.
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Logarithmic or exponential growth phase (log for short)
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At this stage the bacteria have adapted to the new environment and are metabolically active, reproducing exponentially.
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Stationary phase
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Due to the depletion of nutrient and the accumulation of waste products the death rate equals the reate of cell replication.
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Decline or phase death phase
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As nutrient becomes less available and the accumulation of waste products becomes more toxic the death rate exceeds the rate of replication.
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logarithmic growth phase
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What phase are bacteria more easily killed or inhibited?
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log phase
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Many antimicrobial substances act by disrupting metabolism and metabolism is maximal during the ______ ______.
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log phase
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In what phase are the cells dividing so rapidly they don't form thick cell walls, well developed capsules or endospores.
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stationary phase
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Bacterial cells are harder to destroy in the __________ _______ because they tend to have a lower metabolic rate, thick cell walls, and well developed capsules and endospores.
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Tyndallization/Intermittent sterilization
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110'C steam or boiling
30 mins for 3 successive days. |
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Autoclaving
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Steam heat under pressure.
15 PSI, 121'C, for 15 mins. Results in sterilization. |
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Osmosis
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the movement of water across a semipermeable membrane. Water will move from an area of low solute concentration to an area of higher solute concentration.
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Osmotic pressure
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the force with which water moves across a membrane due to a concentration gradient. The amount of solute in the environment surrounding a cell can have a profound effect on the growth of a cell.
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hypertonic
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If the surrounding environment contains a high solute concentration, relative to the interior of the cell, the environment is termed ___________ and there will a net movement of water out of the cell.
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plasmolysis
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The loss of water from the cell will cause the cytoplasm to shrink away from the cell wall and this is called ______________. The loss of water will inhibit the growth of the cells because so many of the cell's metabolic reactions require water.
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halophiles
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Some bacteria called __________ (salt loving) can continue to grow in high salt concentrations.
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hypotonic
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If the surrounding environment has a low solute concentration, the environment is termed __________ and there will be a net movement of water into the cell.
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isotonic
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If the solute concentration is the same inside and outside the cell, the environment is termed __________ and water will move in and out of the cell equally.
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gradient plates
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A double-layered agar plate with a concentration gradient in the upper layer of the agar.
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temperature
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Enzyme activity will increase as the ___________ increases up to a point at which heat will denature the 3-dimensional structure of the enzyme rendering it inactive.
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Enzymes slows down and metabolic activity and growth slow down too.
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What happens to enzymes when temperature is lowered?
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temperature range
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Different bacterial species have different optimal, maximum and minimum growth temps and most grow in a ____________ ______ varying from min to max growth temperature by approximately 20-30'C.
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psychrophiles or psychrophilic
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Bacteria that grow within a temperature range of 0' to 20' C are termed _____________ or ____________.
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mesophiles
mesophilic |
Bacteria the grow optimally in a range of 20-45'C are termed _________ or _________. Normal human body pathogens temperature is 37'C.
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psychrotolerant
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Some organisms that grow optimally in the mesophilic range can also grow, very slowly, at refrigeration temperature and are termed _____________, and some of them produce toxins capable causing food poisoning (food intoxication).
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thermophiles
thermophilic |
Bacteria which grow in a temperature range from approximately 40-70'C are termed ___________ or _____________.
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Hyperthermophiles
Extreme thermophiles |
These have an optimal growth temp of 80'C or higher and are capable of growing in hot springs and geysers.
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dry heat
moist heat |
Heat is the most common and economical means of controlling microbial growth. There are two basic types of heat used, ______ ______ and _______ ______.
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Dry heat methods
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kill microorganisms by denaturing proteins and oxidation (burning) of vital structural and metabolic chemicals.
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Direct flaming
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Every time you flame the lip of a test tube or flame your loop in lab your are using dry heat method of sterization.
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Drying ovens
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This circulates hot air, 171'C for 1 hour, or 160'C for 2 hours, are commonly used to sterilize glassware and metal instruments, oils and powders.
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Incineration
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used to dispose of contaminated materials in health care facilities, and to stop the spread of infectious disease in cattle or poultry by the ___________ the carcasses of infected animals.
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Moist heat methods
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kill microbes primarily by denaturing proteins, but they can also damage cell membranes, and nucleic acids.
more penetration than dry heat and consequently can be effective at a lower temp or in less time. |
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Tyndallization
Intermittent Fractional Sterilization |
can be used to sterilize materials using 100'C steam for 30 mins but requires heating the material to be sterilized on 3 successive days and incubation of the material @ 37'C btwn heat treatments.
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Autoclaving
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uses steam heat under pressure and is one of the most reliable means of sterilization. 15 PSI at 121'C for 15 minutes.
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Pasteurization
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Used in processing milk products, fruit juices, beer and wine.
Doesn't result in sterilization, but kills vegetative pathogens and some microorganisms involved in food spoilage. |
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low-temperature holding
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LTH
pasteurization 63'C for 30 mins |
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high-temperature short time
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HTST
AKA flash method |
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HTST
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pasteurization
72'C for 15 secs |
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Ultra-high-temperature
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UHT
pasteurization raises the temp from 74' to 140'C and rapidly, in less than 5 seconds, lowers the temp back to 74'C. |
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Ionizing radiation
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X rays and gamma rays which are short wavelength, high energy, and very penetrating
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Ionizing radiation
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Because they are of sufficient energy to knock electrons free of atoms, particularly water molecules, forming ions (free radicals).
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Free radicals
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_____ _______ formed in this way can cause lethal damage to cells.
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Ionizing radiation
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also directly impact DNA causing lethal damage.
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ionizing radiation
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Because no is involved, __________ __________ is also used to sterilize heat-labile products such as plastic syringes and surgical gloves.
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Nonionizing radiation
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UV light is of longer wavelength than ionizing radiation.
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Nonionizing radiation
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Wavelengths below 200nm are absorbed by the air and are ineffective in controlling microbial growth except in a vacuum.
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UV light
(nonionizing radiation) |
___ _______ is most lethal at a wavelength of 260-265nm which corresponds to the wavelength that is absorbed optimally by DNA.
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thymine dimers
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As energy from UV light is absorbed, adjacent thymine molecules covalently bond to one another. The resulting _________ _______ disrupt both DNA replication and transcription.
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damages human tissues causing burns
premature aging of the skin skin cancer cause damage to the cornea of the eyes. |
Why is UV light in ionizing radiation of limited use?
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no
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Does UV light penetrate through most materials?
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yes
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Do x-rays and gamma rays penetrate through most materials?
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UVlight
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used to reduce the number of microbes on surfaces and is used to reduce the concentration of airborne microbes in operating rooms, isolation wards, and areas of food preparation
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UV light
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Sewage plants are now using this in the treatment of sewage. It significantly reduces the number of microbes in the water.
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UV light
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Some bacterial cells possess enzymes that allow them to repair the damage done to thier DNA by exposure to ___ _______.
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dark repair
light repair (photorepair) |
What are the names of the enzymes that are involved in repairing damaged DNA by exposure to UV light?
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dark repair
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involves an endonuclease that can function without visible light and is able to remove pyrimidine dimers
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light repair (photorepair)
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involves a pyrimidine dimerase called photoreactivating enzyme which is activated by visible light in the blue and green spectrum.
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photoreactivating enzyme
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Light repair or photorepair involves a pyrimidine dimerase called _______________ _______ which is activated by visible light in the blue and green spectrum.
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Disinfectants
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substances used on inanimate/nonliving objects to kill or inhibit growth of microorganisms.
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Antiseptics
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antimicrobial substances used on living tissue.
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Soaps and Detergents
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surfactants (surface active) and act as wetting agents. They decrease surface tension btwn molecules and emulisify (break up) fats and oils.
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Soaps and Detergents
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poor antimicrobial agents (unless they have an antimicrobial agent added) they work by suspending microorganisms and debris allowing them to be mechanically removed through scrubbing and rinsing.
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Quaternary Ammonium Compounds
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used as both disinfectant and antiseptics.
common ingredient in mouthwash, contact lens solutions and lab bench disinfection solutions. |
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tend to be neutralized by soaps and detergents
inactivated by organic matter readily absorbed by cotton and gauze support growth of pseudomonas. |
What are some disadvantages of Quaternary Ammonium Compounds?
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Organic Acids
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weak acids are used in eyewash solutions, and used to prevent fungal growth in food and soft drinks.
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Heavy metals
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The antimicrobial effect of certain metals in very small amounts is termed oligodynamic action.
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oligodynamic action
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The antimicrobial effect of certain metals in very small amounts is termed _____________ ________.
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vaccines
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Thimerosal, a mercury compound, is used to preserve ________.
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copper sulfate
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_______ _______ is used to control the growth of algae.
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Halogens
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Chlorine and iodine
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(halogen)
Chlorine bleach |
_______ _______ is one of the best cost effective disinfectants available.
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(halogens)
Iodine |
________ in the form of iodophores (iodine + detergent) are used as antiseptics and surgical scrubs.
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tincture
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A ________ (an antimicrobial substance combined with alcohol) of iodine is commonly used as a skin antiseptic.
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Alcohol
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Ethyl and Isoprophyl
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Alcohol
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denature proteins and act as lipid solvents dissolving cell membranes. This does NOT sterilize.
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Isoprophyl
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__________ alcohol acts as a surfactant and is used on the skin to mechanically remove microorganisms from the skin prior to injection or venipuncture.
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Phenols
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Carbolic acid
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Phenols
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Are not activated by organic matter and can be used effectively on vomits, urine, blood, and fecal matter.
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Lysol and Amphyl
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What are some phenolic compounds?
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Chlorinated phenol
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What phenol is used in surgical instruments?
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Gaseous Chemosterilizers
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Ethylene oxide is used to sterilize: rubber gloves, mattresses, plastics and other heat labile materials.
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Oxidizing agents
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Hydrogen peroxide disrupts protein structure and is converted to water and oxygen.
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Phenols
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Carbolic acid
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Phenols
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Are not activated by organic matter and can be used effectively on vomits, urine, blood, and fecal matter.
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Lysol and Amphyl
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What are some phenolic compounds?
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Chlorinated phenol
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What phenol is used in surgical instruments?
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Gaseous Chemosterilizers
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Ethylene oxide is used to sterilize: rubber gloves, mattresses, plastics and other heat labile materials.
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Oxidizing agents
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Hydrogen peroxide disrupts protein structure and is converted to water and oxygen.
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antimicrobial chemotherapy
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the use of chemicals to control infection
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antimicrobial agents
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Microorganisms are becoming increasingly resistant to our first line __________ ______ and some strains are even considered untreatable.
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"magic bullet"
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something that will specifically target and inhibit or destroy a microbe without harming the host.
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antibiotics
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True _________ are antimicrobial substances produced by microorganism.
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Semisynthetic
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___________ antimicrobial agents are naturally produced molecules that have been chemically modified to make them more effective.
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Synthetic
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_________ antimicrobial agents are purely manmade. The term _____ is often used of synthetic agents to distinguish them from true antibiotics.
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antimicrobial agent
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When attempting to treat a patient with an infectious disease a physician needs to make an informed decision concerning which _________ ______ to prescribe.
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resistant
intermediate susceptible |
This susceptibility pattern shows the physician whether the isolate is ________, show __________ resistance, or is __________ (sensitive), to several antimicrobial agents.
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patient allergies
toxicity (side effects) possible interactions with other medications in making a final decision. |
After determining which antimicrobial agents the isolate is suseptible to, what other factors will the physician consider?
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Kirby-Bauer method
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A commonly used, FDA approved, method of determining susceptibility is the _______ _______ _______.
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disk diffusion test
Mueller Hinton |
The Kirby-Bauer method is a standardized _____ _________ _____. A petri dish containing ________ ________ agar, poured to a uniform thickness of 4mm, is covered with a lawn of the organism to be tested.
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antimicrobial agents
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Paper disks impregnated with standardized concentrations of various __________ _____ are placed on the agar surface.
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zone of inhibition
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The plates are incubated and the _____ ___ __________ around each disk is measured and compared to a chart to determine if the organism is resistant, intermediate, or susceptible.
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because different antimicrobial agents diffuse through the agar at different rates. One might have a larger zone of inhibition, but less effective. Different diffusion rates for different antimicrobial agents.
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Why must we measure the zone of inhibition and compare the outcome to the charts?
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Minimum inhibitory concentration
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What does MIC stand for?
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PA
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In the Kirby-bauer method, which organism was the most resistant overall?
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