Ehrlich reaction

Ehrlich reaction - color reaction to indole, which is formed by the decomposition by bacteria tryptophan. Reaction Ehrlich is used in differential microbiological diagnostics: forming indole (reaction Ehrlich positive) Escherichia coli, Proteus, chaeropodidae vibrios and some others; not forming indole (reaction Ehrlich negative) Salmonella (including bacteria typhoid and paratyphoid), Shigella and many others
Indole, reacting with dimethylaminobenzaldehyde, forms connection, painted in red. The reaction is carried out as follows: in broth culture of bacteria contribute 1-2 ml of ether, badly shaken and gently on the tube wall poured 2 ml № 1 (4 g R-dimethylaminobenzaldehyde + 380 ml of 96% ethanol + 80 ml of concentrated hydrochloric acid) and 2 ml № 2 (saturated solution of potassium persulfate). In case not later than 5 minutes of air layer is red, the reaction is positive.

Ehrlich reaction (P. Ehrlich) reaction determine indole. The ability of some species of microorganisms to incolourtag used for differential microbiological diagnostics. As a result of bacterial peptone nutrient medium breaks down into amino acids, of which one (tryptophan) under the influence of tryptophanase split into indole, pyruvic acid and ammonia. For detection of indole use most Ehrlich reaction in the modification Boehme (A. Bohme)to detect indole even in a dilution of 1:1 000 000. In the basis of this reaction is the ability colorless indole in the presence of oxidising agent (potassium persulfate) to form with paradimethylaminobenzaldehyde compound red. Fisher (that is, Fischer)in the reaction are two molecules of indole a single molecule of paradimethylaminobenzaldehyde and is one molecule of water. The reaction proceeds according to the formula:

The Blockers and Lebow (M. Freund, Lebach), along with the reaction can occur connection of one molecule of indole a single molecule of paradimethylaminobenzaldehyde, but only in a waterless environment. Obtained in this way a connection will have the formula:


For the reaction Ehrlich necessary solution # 1 - paradimethylaminobenzaldehyde (4 g), ethanol 96 degrees (380 ml), concentrated hydrochloric acid (80 ml) and the solution № 2 - saturated by heating a solution of potassium persulfate.
When determining indole in the daily culture broth of Hottinger or patoulidou culture by 1% peptone water, add 1-2 ml of ether, and gently shake layer on the wall of the tube first 1-2 ml №1, and then the same amount of solution № 2. In the presence of indole not later than 5 minutes painted all essential layer or the bottom of it. The coloration at a later date or redness only broth with colorless ether layer is not an indicator of the presence in the medium indole.
Forming indole these bacteria: Escherichia coli, Proteus, Vibrio comma and chaeropodidae vibrios, Klebsiella ozaenae and Shigella: Fitting-Schmitz; the large - Sachs 7, 8; Flexner; Boyd 5, 7, 9, 11, 13, 15.
Not forming indole Salmonella (including bacteria typhoid and paratyphoid), Shigella (Grigorieva-Shiga; sonnei, Newcastle; Boyd 1, 2, 3, 4, 6, 8, 10, 12, 14), Соrynebacterium diphtheriae and mn. other