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27 Cards in this Set
- Front
- Back
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BLANK media is used to select and isolate specific types of bacteria through chemical means.
It allows the BLANK of one organism and BLANK another organism. |
Selective media
Growth Inhibits |
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BLANK media contains chemical compounds that allow bacteria to be distinguished from each other.
Usually determined from a change in BLANK growth or a change in BLANK of the media |
Differential
bacterial color |
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BLANK/BLANK media is media that has ingredients to inhibit/select for certain bacteria as well allow for differentiation between bacteria.
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Selective/Differential media
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BLANK indicators are incorporated into the medium to allow changes in pH to be observed as color changes to the medium.
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pH indicators
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Why do microbiologists use special purpose media?
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They are useful in the isolation and detection of bacteria
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Name two examples of human staphylococci
They are Gram BLANK cocci arranged in BLANK-like clusters |
Staphylococcus epidermidis
Staphylococcus aureus positive; grape-like |
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Name two examples of human streptococci
They are BLANK or pairs of Gram BLANK cocci. |
Streptococcus pyogenes
Streptococcus pneumoniae chains; gram positive |
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Hemolysins are exotoxins that cause...
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cause the destruction of red blood cells by disrupting their cell membranes
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What is alpha hemolysis? What is the color change on agar and what causes it?
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Alpha hemolysis is the incomplete lysis of red blood cells.
The green color change is caused by oxidation of the heme iron. |
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What is beta hemolysis? What is the color change on agar and what causes it?
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Beta hemolysis is the complete lysis of red blood cells.
Clear halo is seen on agar because organism uses all the hemoglobin |
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Blood agar is a BLANK medium, made using 5% BLANK blood, and good for observing BLANK activity
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Differential medium
sheep hemolytic |
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Catalase is an enzyme that...
What organisms produce catalase? How do you observe catalase activity? |
converts hydrogen peroxide into water and oxygen gas
Staphylococci; bubbling |
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MSA (mannitol salt) agar is both a BLANK and BLANK medium.
Since it has 7.5% NaCl concentration, only the BLANK genus will grown on MSA agar. |
Selective and differential
Staphylococcus |
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MSA agar has phenol red pH indicator. Acid from mannitol fermentation turns colonies and media BLANK color. Name an example organism.
Non-fermenators have BLANK color. Name an example organism. |
Yellow; Staphylococcus aureus
No (no color change); Staphylococcus epidermidis |
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Family enterobacteriaceae are Gram BLANK rods referred to as BLANK.
They are found in the BLANK tract, are facultatively anaerobic, BLANK (hint: use simple media), and are harmful because they are... |
Gram negative; "enterics"
GI tract; nonfastidious; opportunistic pathogens |
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Enterics can be identified on differential and selective media using pH indicators and the fact that they must...
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ferment different types of carbs to survive
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All enterics can ferment glucose, but only bacteria with these two enzymes can ferment lactose as a sole carbon source.
How will the lactose byproducts change the surrounding media? |
B-galactosidase and lactose permease
Acidic byproducts lower pH of surrounding media |
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Organism that can ferment lactose are called BLANK while those that cannot ferment lactose are called BLANK
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coliforms
paracolons |
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What are the three types of media used with enterics? They all contain what carb/sugar?
They are selective for gram BLANK and inhibitory for gram BLANK through the use of BLANK. |
1. MacConkey agar
2. Eosin Methylene Blue Levine (EMB) agar 3. Salmonella-Shigella (SS) agar All have lactose Gram negative; gram positive; dyes |
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MacConkey agar contains bile salts and BLANK BLANK. It selects for Gram BLANK bacteria.
The pH indicator is... Organisms that can ferment lactose will appear... |
Crystal violet; gram negative
Neutral red Red |
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EMB agar is used to differentiate between enteric BLANK and BLANK fermentors
What are the two dyes and what are they used for? Coliforms will appear BLANK while paracolons will appear BLANK. |
Lactose and non-lactose
Eosin and methylene blue inhibit gram positive bacteria Purple or blue-black with metallic green sheen; colorless but can appear pink/purple |
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SS agar is used to ID BLANK and BLANK enteric species
It has lactose, and what dye to inhibit G+ and some G- bacteria? The neutral red pH indicator leads coliforms to appear BLANK and paracolons BLANK. |
Salmonella and Shigella
Brilliant green dye Red; colorless |
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SS agar contains sodium thiosulfate because some enteric bacteria can use it to...
What is the purpose of ferric citrate? What does it produce on the bacteria? |
can produce colorless hydrogen sulfide gas (H2S) gas.
It is an H2S gas indicator; produces black precipitate. |
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TSI (triple sugar iron) agar allows for differentiation between bacteria based on what three things?
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1. Based on their ability to ferment glucose, lactose, and/or sucrose
2. To produce gas from fermentation 3. Their ability to reduce sulfur to hydrogen sulfide |
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In TSI agar using phenol red pH indicator, acidic conditions are what color? Alkaline?
In TSI slant, how is CO2 or H2 gas detected? How is H2S gas detected (same stuff as in SS agar)? |
Yellow; pink
Gas bubbles or break in the butt of the slant Black precipitate |
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What type of medium can be used to select and differentiate for organisms that can use citrate as a sole carbon source?
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Citrate medium
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Organisms that contain citrase and use citrate turn the bromothymol blue pH indicator what color?
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From green to deep blue
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