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73 Cards in this Set
- Front
- Back
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What is the selective agent in mannitol salts agar?
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carbohydrate mannitol
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What genus does MSA select for?
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Staphlococci
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What is the pH indicator in MSA
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Phenol red
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What does a yellow color change around a colony signify
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Pathogenic Staph
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What do the sugars in EMB encourage?
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growth of fecal coliforms
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what group of bacteria does EMB agar inhibit
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Gram-positive organisms
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What does a green metallic sheen indicate about a colony
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vigorous lactose or sucrose fermentation
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What does a pink-colored colony indicate
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small amounts of acid production; slow lactose fermentation
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What colored colonies do non-fermenters have on EMB agar?
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the coloration of the medium or their normal color
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what is the inhibitory agent in EMB agar?
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Eosin-y and methylene blue dyes
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what are the two primary reasons for using Blood Agar
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isolation and cultivation of fastidious bacteria
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what is beta hemolysis
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complete destruction of RBCs and hemoglobin
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what is alpha hemolysis
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partial destruction of RBCs and hemoglobin
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what is gamma hemolysis
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non-hemolysis
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what are the hemolysins produced by streptococci called?
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streptolysins (O & S); O- labile, minimal activity in anaerobic conditions; S is stable with optimal activity in anaerobic conditions
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what is the snyder test used for?
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measure dental carries susceptibility
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what two groups of oral bacteria does the snyder medium select for?
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lactobacilli and oral strptococci
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what does a positive snyder test look like?
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yellow color
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what is the selective property of the snyder medium
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acidic pH of 4.8
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how is total magnification calculated
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objective X occular
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in bright field microscopy what is used to improve the contrast between the specimen and the background?
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application of stains
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what is numerical aperture
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measure of lens ability to capture light coming from he specimen and use it to make the image
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what objective lens should be used when observing bacterial smears
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100x
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what term refers to clarity of image
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resolution
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what is the limit of resolution
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distance two points must be apart in order to be viewed as separate
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why did we preform a wet mount
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to see the differences in the magnifications and to identify yeast and determine motility
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what organism did we observe on the wet mount
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yeast- saccharonyces cerevisiae
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is the specimen used to prepare a wet mount alive or dead
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alive
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what is the sequence of steps in preparing a wet mount
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place specimen in a drop of water and lower coverslip onto it. Observe using 40, 100, and 400 total mag
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what are the two components of a stain
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solvent and colored molecule
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what is an auxochrome
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charged portion of a chromogen that allows it to act as a dye through ionic or covalent bonds between chromogen and cell
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basic stains are attracted to what type of charge on bacterial cell surfaces
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negative charges
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what are some examples of common basic stains?
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safrin dye bacillus, crystal violet bacillus
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what are the purposes for heat-fixing bacterial smears
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kills bacteria and makes it adhere to glass; coagulates cytoplasmic protein to make them more visible
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what cell characteristics can be identified with a simple stain
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morphology, size and arrangement
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what is meant by ab aseptic transfer
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transfer of microbes from on culture to another without contaminating the original
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after performing a transfer why do we begin sterilization of the loop in the flames inner core
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it heats up the loop gradually drying any culture material to prevent aerosol formation
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why should you allow a flamed loop to cool before touching it on or in a culture
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so that it doesnt burn the culture
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why do we hold the culture tube at an angle
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to prevent contaminents from entering
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what is the purpose of performing a streak plate
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to produce isolated colonies
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what typer of streak patter is used with high cell densities
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quadrant method
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what does the acronym CFU stand for
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colony forming unit
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what is the difference between mixed culture and pure culture
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pure culture is only one type of bacteria and mixed culture is more than one
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what is the prime indication you have a successful streak plate
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when isolation is obtained
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Gram stain is what kind of stain
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differential
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correct sequence of reagent appication in the gram stain
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primary stain-> iodine -> decoloization -> safranin
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color of gram positive stains
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purple
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color of gram negative stains
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pink
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in the gram stain which is the primary stain
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the crystal violet
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in the gram stain which is the mordent
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the iodine
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in the gram stain which is the counterstain
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the safranin
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what characteristics can be determined using the gram stain
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morphology, size and arrangement
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a gram positive stain indicates what cell wall characteristic
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thick peptidoglycan layer and greater degree of cross linking
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what cell wall characteristic is indicative of a gram negative stain
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higher lipid content and thinner peptidoglycan layer
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if a gram positive bacterium is over decolorized what color will the cell be
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reddish
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if the gram negative is undercolorized what color will the cell be?
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purple
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why are gram stains helpful in the medical field?
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can provide rapid ID and data to treat infection
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What type of stain is an acid fast stain?
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differential stain
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what is the correct sequence of reagent application in the Ziehl-Neelson stain?
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1)carbofuchsion 2) decolorization 3) counterstain
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In the ZN stain which reagent is the primary stain?
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Carbofuchsion
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why do we need to use a steam bath in the ZN procedure?
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steam heat drives stain into cell if is not acid fast
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In the ZN stain which is the counter stain?
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Methylene blue
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At the end of the acid fast stainng process, acid fast organisms stain what color
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reddish purple
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At the end of the acid fast stain, non acid fast organisms stain what color
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blue
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a positive acid fast reaction correleates with what cell wall characteristic
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high concentration of wax like lipids
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why are acid fast stains useful in the medical practice
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they detect mycobacterium like tuberculousis
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what does the phrase "ubiquitous in nature" mean
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they are found everywhere
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what is the microbiologists typical first step toward ID of an organism
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visual exam of growth
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why can we determine a significant amount of ID related information from colonies when they are grown under controlled conditions
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they display distinct morphological color and texture
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In a colony counter, colony details are best seen with what kind of light
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transmitted light
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In a colony counter, colony color is best seen with which kind of light
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reflected
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what is a colony counters grid used for
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a counting grid
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what are the basic categories of colonies
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shape, margin, color & texture
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