What color does a positive indole test indicate in Enterobacteriaceae?

What color does a positive indole test indicate in Enterobacteriaceae?

• A. Blue
• B. Red
• C. Green
• D. Yellow

Answer: (B)

A positive indole test in Enterobacteriaceae is indicated by the development of a red color after the addition of a specific reagent, usually Kovac's reagent. This color change occurs due to the presence of indole, which is produced from the amino acid tryptophan by certain bacteria through the action of the tryptophanase enzyme. When Kovac's reagent is added, it reacts with indole to produce a red-colored complex, confirming that the organism can metabolize tryptophan. Therefore, the development of red color signifies a positive result for the indole test, which is an important biochemical characteristic used to differentiate between different species within the Enterobacteriaceae family.

A positive indole test in Enterobacteriaceae is indicated by the development of a red color after the addition of a specific reagent, usually Kovac's reagent. This color change occurs due to the presence of indole, which is produced from the amino acid tryptophan by certain bacteria through the action of the tryptophanase enzyme. When Kovac's reagent is added, it reacts with indole to produce a red-colored complex, confirming that the organism can metabolize tryptophan. Therefore, the development of red color signifies a positive result for the indole test, which is an important biochemical characteristic used to differentiate between different species within the Enterobacteriaceae family.