IMViC Test: Differentiating *E. coli* and *Enterobacter aerogenes*

The IMViC tests (indole, methyl red, Voges-Proskauer, and citrate utilization) are a series of biochemical tests used to differentiate between different species of bacteria.

Indole test:

- E. coli: positive (produces indole)

- Enterobacter aerogenes: negative (does not produce indole)

Methyl red test:

- E. coli: negative (does not produce sufficient acid to turn the indicator red)

- Enterobacter aerogenes: positive (produces sufficient acid to turn the indicator red)

Voges-Proskauer test:

- E. coli: negative (does not produce acetoin)

- Enterobacter aerogenes: positive (produces acetoin)

Citrate utilization test:

- E. coli: positive (can utilize citrate as a sole carbon source)

- Enterobacter aerogenes: negative (cannot utilize citrate as a sole carbon source)

In summary, the IMViC tests can be used to differentiate E. coli from Enterobacter aerogenes based on their different reactions in these tests. E. coli is indole-positive, methyl red-negative, Voges-Proskauer-negative, and citrate-positive, while E. aerogenes is indole-negative, methyl red-positive, Voges-Proskauer-positive, and citrate-negative.