IMViC Series

Purpose of IMViC tests

Differentiates Escherichia coli from the Enterobacter/Klebsiella group

Indole test

Evaluates the ability of bacteria to convert tryptophan to indole

Indole test media

Trypticase soy broth

Indole test reagent

Kovac’s reagent

Positive Indole result

Red color in the reagent layer

Negative Indole result

No color change (remains yellow/amber)

Methyl Red (MR) test

Evaluates the ability to ferment glucose to an acid

MR test indicator

Methyl red

Positive MR result

Red medium (acid present)

Negative MR result

Yellow or orange medium (acid not present)

Voges-Proskauer (VP) test

Evaluates the ability to convert glucose to non-acidic end products like acetoin

VP test reagents

Barritt’s A and Barritt’s B (added in order)

Positive VP result

Pink or rose color after 30 minutes

Relationship between MR and VP

Mutually exclusive; bacteria are typically positive for one and negative for the other

Simmons Citrate test

Evaluates the ability of bacteria to ferment citrate

Citrate test pH indicator

Bromthymol blue

Positive Citrate result

Media changes from green to royal blue

Negative Citrate result

Media remains green