testresults.ppt

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 e-mail your URL so
that I can give you credit.
Fun2Care@yahoo.com
Also, most information was taken from Alfred E. Benson’s Microbiology Applications, Short
Version, 9th Edition

In a Gram stain, what are
the positive and negative results?
© NursingJourney.com

In a Gram stain, what are
Positive: Purple
Negative: Pink

In a spore stain, what are

In a spore stain,what are
Positive: Green spores
Negative: No spores (pink)

In a acid-fast stain,what are

In a acid-fast stain,what are
Positive: Pink
Negative: Blue

http://faculty.southwest.tn.edu/bdrake/Microbiology%20Pictures.htm
What is this? What do the results reveal?

To test if the organism is motile, stab a
depth of 75% of the media and incubate
24-48 hours at the best growth
temperature already decided.
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

Negative result:-
Solid in ice bath or
refrigerator after 5
minutes.
Gelatin Liquefaction - Nutrient Gelatin
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.

Positive result
Green slant in
0-10 minutes
Phenylalanine Deaminase - Phenylalanine agar slant (PA)
Streak slant with inoculator,
After incubation time, use 5
drops of phenalalanine reagent.
Negative result
Yellow slant after
5-10 minutes

Positive Result:
Yellow
(positive for acid)
Bubbles
(positive for gas)
Negative Result:
Red-pink
(negative for acid)
No bubbles
(negative for gas)
Use Durham tube to test for gas, incubate 24-48
hrs. Reincubate negative results up to 30 days.
Glucose, Lactose or Mannitol Fermentation -
Phenol Red, Glucose, Lactose Mannitol Broth

Negative Result
Positive Result
Methyl Red Test
After incubating for 2-5 days, add 3-4
drops of Methyl Red reagent.

Positive Result
Negative Result
Urea hydrolysis - Urea broth
After heavy inoculation,
incubate up to 30 days.

Positive Result
Clear zone
Negative Result
Dark zone
Starch hydrolysis - Starch agar plate (SA)
After incubating 24-48 hrs, add
grams iodine over growth.

Negative Result
Positive Result
Uses citrate as
sole carbon
source
Citrate utilization - Simmon’s citrate agar slant (S/C)
Streak slant and stab butt, Incubate
up to 30 days.

Positive Result
Red ring
Negative Result
Yellow ring
10 drops of Kovac’s reagent are added
after a 24-48 hour incubation.
Tryptophan hydrolysis (indole) - Tryptone broth

Casein hydrolysis - Skim milk agar plate (SMA)
Positive Result
Clear zone
Negative Result
no zone
Incubate for 24-48 hours

http://smccd.net/accounts/case/biol240/vlab.html

http://smccd.net/accounts/case/biol240/vlab.html
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
Litmus reactions - Litmus milk

http://biology.uwsp.edu/faculty/TBarta/

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 24-48 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.

http://people.uleth.ca/~selibl/Biol3200/BiochTests/

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.
Voges-Proskauer Test, aka Acetoin - 1/2 MR-VP media
http://people.uleth.ca/~selibl/Biol3200/BiochTests/

Oxidase Positive
Black colonies
within 30 minutes
Oxidase Negative
No black colonies
After incubation, tamp one oxidase
disk on first quadrant
Oxidase Production - Nutrient agar plate (NA)

Catalase
Production
Positive
Bubbles
Catalase
Production
Negative
No bubbles
Catalase Production - Nutrient agar slant (NA)
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!

http://academic.mwsc.edu/jcbaker/images/nitrate%20reduction.jpg

http://academic.mwsc.edu/jcbaker/images/nitrate%20reduction.jpg
Negative for
Nitrate
Reduction
Clear color
Postive for
Niatrate
Reduction
Red color
Nitrate Reduction - Nitrate agar slant
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.

http://academic.pg.cc.md.us/~kroberts/lecture/web/exoenzymes/lipase.jpg

http://academic.pg.cc.md.us/~kroberts/lecture/web/exoenzymes/lipase.jpg
Negative for
Fat Hyrolysis
No precipitate
Postive for
Fat Hydrolysis
Blue precipitate
Fat Hydrolysis - Spirit Blue agar plate (SBA)
Incubate for 24-48 hours.

Calculate the following dilution:
Using the picture, calculate the
number of cells per milliliter in the
original broth culture if 128 colonies
were counted on plate C1.
A) 128,000,000
B) 130,000,000
C) 1,300,000,000
D) 1,280,000
E) 13,000,000
F) 12,800,000
G) 1,280,000,000
H) 1,300,000
Quoted from a practice practical from
Brookhaven College of DCCCD.

Using the picture, calculate the
number of cells per milliliter in the
original broth culture if 128 colonies
were counted on plate C1.
A) 128,000,000
B) 130,000,000
C) 1,300,000,000
D) 1,280,000
E) 13,000,000
F) 12,800,000
G) 1,280,000,000
H) 1,300,000
Quoted from a practice practical from
Brookhaven College of DCCCD.
The correct answer is: C.
(Remember to round the numbers.)

http://smccd.net/accounts/case/biol230/dilutions2.html#

10-2 10-4 10-5 10-6
The answer is 10-6, or .000001

10-1 10-2 10-3
The answer is 10-3, or .001

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
Fun2Care@Yahoo.com.

testresults.ppt

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