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Brandy GoudreauProfessor Tiffany MartinMedical MicrobiologyM/W/F 8:05am Fall 2016

UNKNOWN LAB REPORT#67 – Salmonella typhimurium

Mon day, November 07 , 20 16

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 , Nov ember 9, 20 16

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 , 20 16

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.

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.

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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.

Data Summary

The following is a summary of tests used to identify unknown #67:

Figure 4: SIM for #67 11/16/2016

Figure 5: MAC for #67 11/16/2016

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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 ureaseSIM Sulfide, Indole, Motility Half stab Black- (+) H2S, yellow later (-) indole not

present, Cloudy. (S+I-M+)MAC Lactose fermentation “modified” streaking for

isolationColorless colonies – (-) for lactose fermentation

Conclusion

Based on the above test results and the concurrence with the provided identification chart, bacteria #67 is Salmonella typhimurium..