DIAGNOSTIC DISCS 50 discs Code: DD 509
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.
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).
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.
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 -).
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.