This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Microbiology Pa 1 (History, Microscopy, Stains and Structure and Physiology of Bacteria), Subject name: Microbiology
Kovac's reagent is used in _____ 
Select and explain. 
A. Methyl red test, B. Voges-Proskauer test, C. Indole test, D. Urease test
C: Indole test
Answer: C: Indole test 
Explanation: Kovac's reagent is used in Indole test Indole test is used to determine the ability of an organism to split amino acid tryptophan to form the compound indole. Indole production is detected by Kovac's or Ehrlich's reagent which contains 4 (p)-dimethylamino benzaldehyde, this reacts with indole to produce a red colored compound. negative indole test positive indole test