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Brandy Goudreau
Professor Tiffany Martin
Medical Microbiology
M/W/F 8:05am Fall 2016
#67 – Salmonella typhimurium
Monday, November 07, 2016
Unknown #67 was identified as a gram-negative organism by completing a gram stain. The results
demonstrated pink, rod shaped cells. Because this tested negative there was no need for the catalase test.
Wednesday, November 9, 2016
Based on the gram stain observations, two tests were chosen to be inoculated.
Triple Sugar Iron slant or the TSI slant was selected to differentiate the carbohydrate fermentation.
Stab the butt and streak the slant method was also used for inoculation.
Urea Broth was selected as an enzyme test. An organism producing the enzyme urease will break down
the urea into ammonia and carbon dioxide. This gives the media an alkaline pH. This is inoculated by
the dip and swish technique.
Figure 1: Gram Stain view from
microscope #67 11-7-16

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All of the inoculated media was left to incubate for 48 hours at about 35°C.
Friday, November 11, 2016
The results are based on a 48-hour incubation period. All test results were cross-referenced against the
provided identification chart and by notes that were provided in lab.
TSI slant was selected as a differential due to carbohydrate fermentation.
The slant showed red/pink in the which was (-) for carbohydrate
fermentation. This was alkaline. There were 2 small bubbles found in the
butt of the tube, which was not what was expected. There was black in the
butt of the tube which indicated that there was H2S.
Bubble #1
Bubble #2
Figure 2: TSI slant for #67
11/11/2016

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Urea Broth was selected as an enzyme test. An organism producing the enzyme urease will break down
the urea into ammonia and carbon dioxide. This gives the media an alkaline pH. This test result was
peach which meant it was (-) for urease.
Figure 3: Urea broth for #67 11/11/2016
These two results meant the remaining bacteria possibilities to only 3. Due to these results, the next 2
media chosen to be inoculated were the Sulfide, Indole, Motility test or the SIM and the MacConkey
agar or the MAC. These were not inoculated until Monday, November 14, 2016.
Monday, November 14, 2016
Sulfide, Indole, Motility test or the SIM was chosen to see if indole, sulfide, or motility is present in
the bacteria. This is inoculated by a half stab into the gel like material. This is not a slant.

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MacConkey agar or the MAC was chosen to isolate and differentiate gram negative organisms. It will
help identify lactose fermentation. This is inoculated by a “modified” streaking for isolation technique.
The initial streak is a lawn streak.
All of the inoculated media was left to incubate for 48 hours at about 35°C.
Wednesday, November 16, 2016
SIM results indicated that there was blackening of the media. This
means that there is hydrogen sulfide production. The Kovac reagent is
added to the top layer after incubation. These results were yellow and
indicates that Indole is not present. Because the media turned black it
was difficult to tell the cloudiness away from the stab line. The results
were read as a positive for motility.
MAC results were (-) for lactose fermentation. There is
no pink anywhere in the colonies therefore these are
colorless colonies.
Figure 4: SIM for #67
11/16/2016
Figure 5: MAC for #67
11/16/2016

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Data Summary
The following is a summary of tests used to identify unknown #67:
MEDIA PURPOSE OF TEST INOCULATION
METHOD
TEST RESULTS
TSI slant
Carbohydrate fermentation Stab the butt,streak the slant (Slant- Alkaline) (Butt- Acidic) (Gas - +)
(H2S (+) )
Urea Broth Differential – Enzyme test Dip and swish Peach – (-) for urease
SIM Sulfide, Indole, Motility Half stab Black- (+) H2S, yellow later (-) indole not
present,Cloudy. (S+I-M+)
MAC Lactose fermentation “modified” streaking for
isolation
Colorless colonies – (-) for lactose
fermentation
Conclusion
Based on the above test results and the concurrence with the provided identification chart, bacteria #67
is Salmonella typhimurium..