kovacs reagent

[michimichi]

1. what is the storage temp.for prepared Kovacs reagent
2. can i add the Kovacs reagent directly to positive Lauryl Tryptose Broth to detect e.coli or do i have to use Tryptophan broth?

[canalon]

1. We used to put it at 4°C, and never had problems
2. You have to use tryptophan broth to avoid false negative.

[michimichi]

can an indole test (kovacs) alone can prove that a water sample has e.coli ?
about the storage of kovacs - i stored it at room temp , so it isnt acceptable.?
can i use peptone water as a subtitute for tryptophan?

[canalon]

No.
Don't know, but considering the ingredients, I imagine that the problem is more the stability of the coloring agent. It might be OK.
That is what I used. Peptone broth has enough aa including tryptophane that it was considered as a good substrate for indole reaction.