Triple Sugar Iron Agar A close-up of the TSIA tube is provided with fields for y
ID: 69135 • Letter: T
Question
Triple Sugar Iron Agar
A close-up of the TSIA tube is provided with fields for you to input results for (1) hydrogen sulfide production, (2) gas from glucose, and (3) acid from glucose. Why does it make sense that no fields are provided for recording whether lactose and/or sucrose are also used?
The image shows the red medium has been changed to uniformly yellow, and cracks have formed as the agar has been pushed up from the butt of the tube. Interpret these observations and note the results in the software. Record the results observed in the software and in the table below.
Organism
Acid from glucose (+/-)
Gas from Glucose (+/-)
H2S production (+/-)
MT1-Escherichia coli
MT2-Enterobacter aerogenes
MT3-Salmonella typhii
MT4-Proteus vulgaris
Which of the four microbes is/are not likely to be positive for lactose or sucrose use? Explain your reasoning.
Which of the microbes (if any) produce H2S (hydrogen sulfide)?
Organism
Acid from glucose (+/-)
Gas from Glucose (+/-)
H2S production (+/-)
MT1-Escherichia coli
MT2-Enterobacter aerogenes
MT3-Salmonella typhii
MT4-Proteus vulgaris
Explanation / Answer
Sucrose, lactose and glucose are the sugars present in Triple sugar Iron. If red slant/yellow butt means only fermentation of glucose has occurred; yellow slant/yellow butt means lactose and/or sucrose fermentation has occurred. So there is no need of separate column showing the fermentation of sucrose and/ lactose. By simply seeing the color change in butt or slant one can identify which sugar fermented.
Organism
Acid from glucose (+/-)
Gas from Glucose (+/-)
H2S production (+/-)
MT1-Escherichia coli
-
+
-
MT2-Enterobacter aerogenes
+
+
-
MT3-Salmonella typhii
+
-
+
MT4-Proteus vulgaris
+
-
+
Which of the four microbes is/are not likely to be positive for lactose or sucrose use? Explain your reasoning.
Salmonella typhi is not positive for lactose or sucrose. Here only the slant will become red because of glucose fermentation where as the butt remains in yellow color showing the bacteria is not able to ferment lactose or sucrose. Through this characteristic we can differentiate salmonella from other enterobacteria.
Which of the microbes (if any) produce H2S (hydrogen sulfide)?
Salmonella typhii and Proteus vulgaris produces H2S causes darkening in the media due to the precipitate formation.
Organism
Acid from glucose (+/-)
Gas from Glucose (+/-)
H2S production (+/-)
MT1-Escherichia coli
-
+
-
MT2-Enterobacter aerogenes
+
+
-
MT3-Salmonella typhii
+
-
+
MT4-Proteus vulgaris
+
-
+
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