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76 Cards in this Set
- Front
- Back
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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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stains
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what is numerical aperture
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the measure of lens ability to "capture" light from coming from the specimen and use it to make the image ex. oil immersion
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what objective lens should be used when observing bacterial smears?
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oil immersion 1000x
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term used for clarity of image
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resolution
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what is the limit of resolution
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an actual measurement of how far apart 2 points must be in order for the microscope to view them as being separate
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why we perform a wet mount
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to observe living cells to determine motility, cell size, arrangement, shape, and to identify a microbe
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organisms observed on wet mount
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yeast
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specimen used to prepare a wet mount dead or alive?
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alive
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what is the sequence of steps in preparing a wet mount
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1-using loop place drop of water in center of slide
2-flame loop, allow to cool 3-obtain a loopful of yeast specimen and add to drop of water 4-observe yeast |
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what are the 2 components of a stain?
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a solvent (usually water or ethonol) and colored, chromogen
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what is an auxochrome
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the charged part of chromagen and helps die stick to cells and work as die
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basic stains are attracted to what type of charge on bacterial cell surfaces?
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negative
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what are some examples of common basic stains?
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methylene blue, crystal violet, and safranan
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what are the purposes for heat fixing bacterial smears? (3)
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1-it kills the bacteria,
2-makes them adhere to the slide 3-coagulate cytoplasmic proteins to make them more visabile |
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what cell characteristics can be determined with a simple stain?
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the cell size, shape, and morphological arrangement
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what is meant by an aseptic transfer
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transfer microbes without containmination
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what are the 2 stages in an aseptic transfer?
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aseptically obtaining a sample from the medium with growth and aseptically transferring that growth to uninoculated medium
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after performing a transfer why do we begin sterilization of the loop in the flame's inner cone?
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to prevent aerosol formation (so we don't inhale the specimen)
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why should you allow a flamed loop to cool before touching it on or in teh culture
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could kill/destroy the culture
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why do we hold culture tube at an angle
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to prevent contamination from entering
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3 reasons culture tubes should never be layed down on the bench
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1. to avoid spills
2. avoid rolling off bench 3. clogging tube vents |
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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 type of streak pattern is used with high cell densities
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quadrant method
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what type of streak pattern is used with low cell densities?
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loose or fishtail
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what does CFU stand for?
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colony forming units
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the difference between mixed culture and pure culture
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pure=1colony mixed=many organisms placed together
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what is the prime indication you have a successful streak plate
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individual colonies form on the streak line
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the gram stain is classified as what type of stain?
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differential stain
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what is the correct sequence of reagent application in the gram stain?
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1-primary=crystal violet
2-mordont=iodine 3-decolorizaion=ethonol 4-counterstain=safranin |
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at the end of the gram stain process, gram positive organisms stain what color?
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purple
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at end of gram stain process, gram negative organisms stain what color?
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redish pink
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in gram stain what reagent is the primary stain
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crystal
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in gram stain which reagent is mordent?
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iodine
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in gram stain which reagent in the counterstain?
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safranin
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besides the gram rxn, what characteristics of the stained organism can be determined using the gram stain?
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cell morphology, size, arrangement
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gram positive rxn correlates with what cell wall characteristics?
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thicker peptidoglycan
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gram negative rxn correlates with what cell wall characteristics
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higher lipid content due to outer membrane and thiner peptidoglycan
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if gram positive bacterium is over decolorized what color will the cells be?
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redish
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if gram negative bacterium is under decolorized what color will the cells be?
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purple
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why are gram stains useful in medical practice?
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rapid, presumption identification of the organism of elimination of a particular organism is possible
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acid fast stains are classified as what type of stain?
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differential
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what is the correct sequence of reagent application in the Ziehl-Neelsen stain?
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1-carbofusionisn
2-decolorization with acid alcohol 3-meth blue |
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in the ziehl-neelsen stain, which reagent is the primary stain?
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carbolfuchsin
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why do we need to use a steam bath in the Ziehl-neelsen procedure?
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-to enhance the carbolfuchisn stain by driving stain into cell
-to make stain more lipid soluble and penetrated cell wall |
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in the ziehl-neelsen stain which reagent is the counter stain?
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methylene blue
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at the end of the acid fast staining process, acid fast organisms stain what color?
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red
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at the end of the acid fast staining process, non-acid fast organisms stain what color?
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blue
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a positive acid fast rxn coorelates 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 medical practice
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-useful in identifying bacilli
-rapid -preliminary diagnosis of TB -can be used to track the progress of antiobiotic therapy -determine their degree of contagiousness |
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What does the phrase "ubiquitous in nature" mean?
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everywhere
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what does "free living mean"?
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can survive anywhere on its own and doesnt need a host organism
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what is the microbiologist's typical 1st step towards identification of an organism?
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visual examination of its growth
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why can we determine a significant amount of identification-related information from colonies when they are grown under controlled conditions?
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they produce a great variety of cultured characteristics
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in colony counter, colony details are best seen with what kind of light?
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transmitted
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in colony counter, colony color is best seen with what kind of light?
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reflective
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what is a colony counter's grid used for
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counting aid
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what are the basic categories (characteristics) of colonies?
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colony shape, margine,elevation, color, and texture
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what are the selective agent in mannitol salts agar?(MSA)
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sodium chloride
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what genus does MSA select for?
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stapholococci
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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 in MSA?
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pH less than 6.8 and staphloyocci (usually S or aureus)
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what do the sugars in encourage (EMB)?
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growth or fecal coliforms
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what group of bacteria does EMB agar inhibit?
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gram positive organism
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what does a green metallic sheen indicate about a cology (EMB)?
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-acidic conditions
-indicator of lactose or sucrose fermentation typical or fecal coliforms |
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what does a pink-colored colony indicate?(EMB)
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small amount of acid
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what colored colonies do non-fermenters have on EMB agar?
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remain their normal color or take on the color of the medium
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what in the inhibitory agent in EMB agar?
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the dyes eosin y and methylene blue
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what are the 2 primary reasons for using BA
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-isolation and culturation of many types of fastidious bacteria
-to differentiate on hemalysis characteristics |
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what is beta hemolysis?
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complete destruction
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what is alpha hemolysis
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partial destruction of rbc's and produces a greenish discolor of the agar around the colonies
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what is gamma hemolysis
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non-hemolysis and appears as simple grown with no chance to the medium
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what are the hemolysins produced by streptococci called?
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streptolycine
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what is the snyder test used for?
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measure of dental carries seseptibility
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what 2 groups of oral bacteria does the snyder medium select for
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lactobacilli and oral streptoccoci
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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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low ph 4.8 + glucose
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