Kovac’s Indole Reagent 100 ml

Kovac’s Indole Reagent 100 ml

SKU : L-1275.0100

CAS : Not available

Formula : Not available

Grade : for microbiology

Primary Diagnostic Uses

E. coli Verification: It serves as a rapid confirmatory test for E. coli in clinical, food-safety, and water-quality testing labs.
Differentiating Proteus Species: It helps microbiologists rapidly separate Proteus vulgaris (indole-positive) from Proteus mirabilis (indole-negative), which is crucial for determining appropriate antibiotic treatment pathways for urinary tract infections.

Kovac’s Indole Reagent is a diagnostic biochemical solution used in microbiology to determine whether a bacterial species can biochemically break down the amino acid tryptophan into indole.

It is a core component of the classic IMViC series of tests (Indole, Methyl Red, Voges-Proskauer, Citrate) used by medical and laboratory teams to differentiate and identify members of the Enterobacteriaceae family—such as distinguishing pathogenic Escherichia coli (indole-positive) from Enterobacter or Klebsiella species (generally indole-negative).

The Reaction Mechanism

When bacteria are grown in a tryptophan-rich broth (like Peptone Water) and Kovac’s reagent is added:

The isoamyl alcohol extracts any free indole to the top layer of the liquid.
The indole reacts with DMABA in the presence of acid to form a cherry-red quinonoid dye complex.
Positive Result: A distinct, vibrant cherry-red ring forms at the top solvent layer (e.g., Escherichia coli).
Negative Result: The top layer remains yellow or amber-brown, indicating no indole was produced (e.g., Klebsiella pneumoniae).