1. Microbiology Quiz Basic Lab Tests
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Microbiology Quiz Basic Lab Tests
FYI, in this quiz there may be words used such as slant, but the photo doesn’t show the media as a slant. Therefore, just think about what you use in your lab, and relate that to what you are seeing here.
Photos have been “borrowed” from the internet. If they are yours, please your URL so that I can give you credit.
Also, most information was taken from Alfred E. Benson’s Microbiology Applications, Short Version, 9th Edition

2. In a Gram stain, what are the positive and negative results?
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In a Gram stain, what are the positive and negative results?

3. In a Gram stain, what are the positive and negative results?
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In a Gram stain, what are the positive and negative results?
Positive: Purple
Negative: Pink

4. In a spore stain, what are the positive and negative results?
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In a spore stain, what are the positive and negative results?

5. In a spore stain,what are the positive and negative results?
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In a spore stain,what are the positive and negative results?
Positive: Green spores
Negative: No spores (pink)

6. In a acid-fast stain,what are the positive and negative results?
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In a acid-fast stain,what are the positive and negative results?

7. In a acid-fast stain,what are the positive and negative results?
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In a acid-fast stain,what are the positive and negative results?
Positive: Pink
Negative: Blue

8. What is this? What do the results reveal?
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What is this? What do the results reveal?

9. Motility Test Media - MTM
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What is this? What do the results reveal?
Motility Test Media - MTM
Negative for Motility Growth is confined to the stab area.
Positive for Motility Growth is radiating from the stab area, cloudiness is present
To test if the organism is motile, stab a depth of 75% of the media and incubate hours at the best growth temperature already decided.

10. What is this? What do the results reveal?
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What is this? What do the results reveal?

11. What is this? What do the results reveal?
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What is this? What do the results reveal?
Gelatin Liquefaction - Nutrient Gelatin
Negative result:-Solid in ice bath or refrigerator after 5 minutes.
Positive result: Liquid in ice bath or refrigerator after 5 minutes.
Stab straight to bottom with an inoculating needle. Put in ice bath or refrigerator for 5 minutes, read results. If negative, reincubate up to 30 days.

12. What is this? What do the results reveal?
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What is this? What do the results reveal?

13. What is this? What do the results reveal?
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What is this? What do the results reveal?
Phenylalanine Deaminase - Phenylalanine agar slant (PA)
Positive result Green slant in minutes
Streak slant with inoculator, After incubation time, use 5 drops of phenalalanine reagent.
Negative result Yellow slant after 5-10 minutes

14. What is this? What do the results reveal?
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What is this? What do the results reveal?

15. What is this? What do the results reveal?
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What is this? What do the results reveal?
Glucose, Lactose or Mannitol Fermentation Phenol Red, Glucose, Lactose Mannitol Broth
Negative Result:
Red-pink (negative for acid)
No bubbles (negative for gas)
Positive Result:
Yellow (positive for acid)
Bubbles (positive for gas)
Use Durham tube to test for gas, incubate hrs. Reincubate negative results up to 30 days.

16. What is this? What do the results reveal?
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What is this? What do the results reveal?

17. What is this? What do the results reveal?
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What is this? What do the results reveal?
Methyl Red Test
Positive Result
Negative Result
After incubating for 2-5 days, add 3-4 drops of Methyl Red reagent.

18. What is this? What do the results reveal?
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What is this? What do the results reveal?

19. What is this? What do the results reveal?
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What is this? What do the results reveal?
Urea hydrolysis - Urea broth
Positive Result
Negative Result
After heavy inoculation, incubate up to 30 days.

20. What is this? What do the results reveal?
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What is this? What do the results reveal?

21. What is this? What do the results reveal?
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What is this? What do the results reveal?
Starch hydrolysis - Starch agar plate (SA)
Positive Result
Clear zone
Negative Result
Dark zone
After incubating hrs, add grams iodine over growth.

22. What is this? What do the results reveal?
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What is this? What do the results reveal?

23. What is this? What do the results reveal?
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What is this? What do the results reveal?
Citrate utilization - Simmon’s citrate agar slant (S/C)
Negative Result
Positive Result
Uses citrate as sole carbon source
Streak slant and stab butt, Incubate up to 30 days.

24. What is this? What do the results reveal?
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What is this? What do the results reveal?

25. What is this? What do the results reveal?
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What is this? What do the results reveal?
Tryptophan hydrolysis (indole) - Tryptone broth
Positive Result Red ring
Negative Result Yellow ring
10 drops of Kovac’s reagent are added after a hour incubation.

26. What is this? What do the results reveal?
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What is this? What do the results reveal?

27. What is this? What do the results reveal?
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What is this? What do the results reveal?
Casein hydrolysis - Skim milk agar plate (SMA)
Positive Result Clear zone
Negative Result no zone
Incubate for hours

28. What is this? What do the results reveal?
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What is this? What do the results reveal?

29. What is this? What do the results reveal?
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What is this? What do the results reveal?
Litmus reactions - Litmus milk
A = Alkaline
C = Acid
D = Litmus Reduction
E = Peptonization
(Another result may be coagulation, but is hard too distinguish in a photo.)
1-5 days incubation time

30. What is this? What do the results reveal?
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What is this? What do the results reveal?

31. What is this? What do the results reveal?
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What is this? What do the results reveal?
Hydrogen Sulfide Production - Kliger’s iron agar slant (KIA)
Lactose Negative
Red Slant
Glucose Positive Yellow butt
Hydrogen Sulfide Positive Black butt
Streak slant for lactose, stab butt for glucose. Incubate hours. Save in refrigerator for new working stock. Lactose positive would be a yellow slant, and Glucose negative would be a red butt. If it is H2S+ negative, there will not be any black visible.

32. What is this? What do the results reveal?
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What is this? What do the results reveal?

33. What is this? What do the results reveal?
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What is this? What do the results reveal?
Voges-Proskauer Test, aka Acetoin - 1/2 MR-VP media
Voges-Proskauer Negative
Brown color
Voges-Proskauer Positive
Red color
Add a dropperful of Barritt’s reagent A&B, after incubating for 5 days, and shake well for 2 hours.

34. What is this? What do the results reveal?
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What is this? What do the results reveal?

35. What is this? What do the results reveal?
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What is this? What do the results reveal?
Oxidase Production - Nutrient agar plate (NA)
Oxidase Negative
No black colonies
Oxidase Positive
Black colonies within 30 minutes
After incubation, tamp one oxidase disk on first quadrant

36. What is this? What do the results reveal?
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What is this? What do the results reveal?

37. What is this? What do the results reveal?
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What is this? What do the results reveal?
Catalase Production - Nutrient agar slant (NA)
Catalase Production Negative
No bubbles
Catalase Production Positive
Bubbles
After a working stock has been incubated for 3-5 days, add 3 drops of hydrogen peroxide. Make sure to use an OLD working stock for this test!

38. What is this? What do the results reveal?
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What is this? What do the results reveal?

39. What is this? What do the results reveal?
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What is this? What do the results reveal?
Nitrate Reduction - Nitrate agar slant
Postive for Niatrate Reduction
Red color
Negative for Nitrate Reduction
Clear color
Incubate, and then add 3 drops of Nitrate reagents A & B. If a negative result occurs, confirm the result with zinc dust. Opposite color results will occur: Clear positive, red negative for nitrate reduction.

40. What is this? What do the results reveal?
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What is this? What do the results reveal?

41. What is this? What do the results reveal?
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What is this? What do the results reveal?
Fat Hydrolysis - Spirit Blue agar plate (SBA)
Postive for Fat Hydrolysis
Blue precipitate
Negative for Fat Hyrolysis
No precipitate
Incubate for hours.

42. Calculate the following dilution:
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Calculate the following dilution:

43. Calculate the following dilution:
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Calculate the following dilution:
The correct answer is: C. (Remember to round the numbers.)

44. Calculate the following dilution:
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Calculate the following dilution:

45. Calculate the following dilution:
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Calculate the following dilution:
The answer is 10-6, or

46. Calculate the following dilution:
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Calculate the following dilution:

47. Calculate the following dilution:
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Calculate the following dilution:
The answer is 10-3, or .001

48. Microbiology Quiz Basic Lab Tests
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Microbiology Quiz Basic Lab Tests
Congratulations!! That’s all for this Microbiology quiz!
Please remember, your instructor may require you to learn more, or less, of what is on this PowerPoint.
It’s your responsibility to learn what you will be tested on!! (Including knowing if any errors were made.) Please report any errors to