New Material Study Flashcards
Sam wants to differentiate streptococci based on the ability to hemolyze red blood cells. What agar will they use?
Blood agar.
Beta hemolysis does what?
Complete breakdown of RBCs resulting in clearing around the colonies.
If you want to select for only gram positive organisms and inhibit growth of gram negative organisms, what agar would you use?
PEA (Phenylethyl alcohol agar).
If you want to differentiate staph species based on whether they are pathogenic or not, what agar would you use?
MSA (Mannitol Salt agar).
Can S. aureus ferment mannitol? What color would it be in the MSA?
Yes. Yellow.
If you want to isolate gram negative coliforms by use of lactose fermentation, what agar would you use?
EMB or MA.
Sam wants to use the Phenol Red (Sugar) test to see if the organism can ferment sugar used in the broth. The liquid in the tube turns violet. Can it ferment the sugar?
No.
Sam wants to see if the organism can dissolve gelatin. The liquid in the tube remains a liquid after inoculation. Can it dissolve gelatin?
Yes.
Sam wants to see if his organism can use citrate as a carbon source. The organism turns blue in the slant. Can it use citrate?
Yes.
What color does the inoculation turn with the Methyl Red test if it cannot produce acid from glucose fermentation?
Yellow.
If the OF tubes both turn yellow, can if ferment or oxidize sugars under the OF test?
Ferment = yes Oxidize = maybe
If the inoculation turns salmon-colored, under the urease test, can it use urea as a nitrogen source?
Yes (slowly).
What color does the inoculation turn if it can convert nitrate to nitrite?
Red.
What color is the inoculation if you add zinc and it metabolizes nitrate to N2 or NO gas?
Light colored.
Sam adds Kovac’s Reagent to their inoculation and the top layer of the liquid turns pink. Under the SIM test, can it break down Tryptophan?
Yes.
The inoculation is yellow after the ‘S’ part of the SIM test. Can it produce Hydrogen Sulfide?
No.
TSI test: what color does the inoculation turn if it cannot ferment glucose?
Violet.
TSI test: what color does the inoculation turn if it can ferment lactose or sucrose?
Yellow.
What color does the inoculation turn if it can produce Hydrogen Sulfide?
Black.
MRVP test: Sam adds VP reagents A and B to their tube. The color turns a blood-orange. What does this mean?
This means that the organism can produce a neutral product from glucose fermentation.
Motility agar: if only the stab in the inoculation turns red, what does this mean?
That the organism cannot swim.
If nitrate reagents A and B are added to an inoculation and it turns red the first time, what does this mean?
That the organism changed nitrate to nitrite.
What does TSI stand for?
Triple-Sugar Iron
Sam adds peroxide to a slide with an organism and it begins to bubble. What does this mean?
This means that it can break down hydrogen peroxide.
