Diagnostic device > Diagnostic discs
DIAGNOSTIC DISCS 50 discs Code: DD 509
ITEST INDOL
for the rapid detection of tryptophanase
Purpose and usage:
INDOL diagnostic discs are designed for detection of tryptophanase. The test enables a rapid presumptive differentiation of some Enterobacteriaceae, for inst. E.coli and Y. pseudotuberculosis, or E. coli and Sh. sonnei.
Principle:
The test is based on the detection of indol which develops at the enzymatic cleavage of tryptophan. The presence of indol is demonstrated by adding the solution of para-dimethylaminobenzaldehyde (Ehrlich reagens).
Technique:
Prepare a dense suspension (degree No.3 of McFarland turbidity scale) from the examined strain in a test tube with 0.4 ml sterile distilled water. Put INDOL disc to the test tube with the suspension and incubate for 3 hours at 37oC. Add a drop of Ehrlich reagent after the incubation and observe the changes of colour.
Evaluation:
A red ring develops on the surface of the suspension if the reaction is positive (INDOL +). The ring is yellow if the reaction is negative (INDOL -).
Warning:
1. INDOL discs are designed for laboratory use only.
2. Discs should be stored in a dark place at +4oC and should not be used beyond the expiration date shown on the packing.
