Question

The results of IMViC test to differentiate E. coli and Enterobacter aerogenes is as follows
i) E. coli is positive for Indole and Methyl red tests
ii) Enterobacter aerogenes is positive for Indole and Methyl red tests
iii) E. coli is positive for Voges Proskauer’s and Citrate utilization tests
iv) Enterobacter aerogenes is positive for Voges Proskauer’s and Citrate utilization tests
Choose the correct answer from the options given below:

• A. Both (i) and (iv) are correct
• B. Both (i) and (ii) are correct
• C. Both (iii) and (iv) are correct
• D. Both (ii) and (iii) are correct

Hint:

Memorize the classic IMViC patterns: E. coli is positive-positive-negative-negative (++--), while Enterobacter aerogenes is negative-negative-positive-positive (--++).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The IMViC series (Indole, Methyl Red, Voges-Proskauer, and Citrate) is a set of biochemical tests used to differentiate members of the family Enterobacteriaceae, particularly coliform bacteria.

Step 2: Detailed Explanation:
Let us analyze the biochemical profiles:
{Escherichia coli has a typical IMViC reaction pattern of ++--.
Indole positive: Produces tryptophanase to convert tryptophan to indole.
Methyl Red positive: Performs mixed-acid fermentation, lowering the pH below
Voges-Proskauer negative: Does not perform butanediol fermentation to produce acetoin.
Citrate negative: Lacks citrate permease to use citrate as a sole carbon source.
This matches statement (i).
{Enterobacter aerogenes has the inverse IMViC pattern of --++.
Indole negative and Methyl Red negative.
Voges-Proskauer positive (produces acetoin).
Citrate positive (utilizes sodium citrate).
This matches statement (iv).
Therefore, statements (i) and (iv) are correct.

Step 3: Final Answer:
Both statement (i) and statement (iv) are correct.