Laura,

We use 0.5% TTC in our lab to help us differentiate colonies from particles.
We run our test with media that does not contain the TTC and at the end of
the incubation period, we flood the plate with the TTC and allow it to stand
for about one hour to allow it to soak into the media and reach the
subsurface colonies.  We then subculture the colonies immediately and have
not yet had any problems with recovery.  This method has worked quite nicely
for us.  We have no experience with adding the TTC to the media prior to
pouring the individual plates, so I cannot comment on the inhibitory effects
of the TTC when used in that manner.

Karen Lynch
Parke-Davis Research



 -----Original Message-----
From: Laura Acevedo [mailto:[log in to unmask]]
Sent: Thursday, October 14, 1999 6:33 PM
To: [log in to unmask]
Subject: [PMFLIST] Inhibitory effect of TTC.



Dear colleagues,

I perform microbial limit tests using poured plates . With some products
(lactose, starch) it is difficult to distinguish the colonies. I know
there`s the recomedation of using MPN in this cases, but I wonder if it is
possible to use poured plates adding  TTC to the culture medium to stain the
colonies and differentiate them from the product being tested. Has anybody
validated this method? I`ve heard about possible inhibitory effect of TTC.
Could someone refer me any paper on this topic?
Any help would be appreciated, thanks in advance,

Laura Acevedo
Microbiological Quality Control Manager
Laboratorio LIBRA
Montevideo-Uruguay
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