Supplements and additives
Kovac's Reagent
For the detection of microbial indole.
- Cat. No.
- LC-5205
- Category
- Supplements and additives
- Format
- 100 mL flask
- Storage
- 2 to 8 °C
- Minimum guaranteed shelf life
- 15 months
Kovac's Reagent is a reagent used for the detection of microbial indole.
Key features
Applications
Confirmation of indole positive microorganisms.
Industry
Food, water.
Preparation
Add 4-5 drops to the tube after 24-48 hours of incubation at 35 °C; shake gently.
Principles and uses
Bacteria that possess the enzyme tryptophanase are capable of cleaving and deaminating tryptophan with the production of indole. The indole test is based on the formation of a dark red dye when the liberated indole reacts with 4-dimethylaminobenzaldehyde. Indole production is an important characteristic in the identification of many microorganisms, especially to differentiate E. coli (+) from other Enterobacteriaceae.
For the detection of indole, the microorganisms must be grown aerobically in a glucose-free environment with plenty of tryptophan (Urea Indole Broth (LC-1227); Peptone Water (LC-1403); SIM Medium (LC-1514); Tryptophan Culture Broth (LC-1237); MIO Medium (LC-1510); Indole Nitrate Medium (LC-1504); Lauryl Sulfate Chromogenic Broth (LC-1465), etc.). Peptone water is particularly suitable as a substrate in the study of indole production.
A positive reaction is denoted by the appearance of a pink-red color on the top of the tube. Negative reactions remain colorless or slightly yellow.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Liquid |
| Color of the dehydrated medium | N/A |
| Color of the prepared medium | N/A |
| Final pH (25 °C) | N/A |
| Storage | 2 to 8 °C |
Formula
| Ingredient | g/L |
|---|---|
| 4-Dimethylaminobenzaldehyde | 50 |
| Hydrochloric acid 37% | 250 mL |
| 1-Butanol | 750 mL |
Preparation and use
Instructions for use
- Lightly inoculate the medium substrate with the microorganism to analyze.
- Incubate 24-48 hours at 35 °C.
- Add 4-5 drops of Kovac's Reagent to the tube and shake gently.
Quality control
Microbiological test
Incubation conditions: 35 °C / 24-48 h / anaerobic atmosphere.
| Microorganism | Characteristic reaction |
|---|---|
| Salmonella typhimuriumATCC 14028 | Indole (-) |
| Escherichia coliATCC 25922 | Indole (+), pink-red color |
Bibliography
- N. Kovacs, Eine vereinfachte Methode zum Nachweis der Indolbildung durch Bakterien. Z. Immunitats. Forsch. Exp. Ther., 55, 311 (1928).
- Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.
- H.H. Gadebusch, S. Gabriels, Modified Stable Kovacs's Reagent for detection of Indol. Am. J. Cli. Pathol., 26, 1373 (1956).
What you receive
The product
Shipped under controlled temperature when the product requires it.
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