Kim, 

Leica sells a spray-reagent that is supposed to disinfect the cryostat while
still cold. However, I have never seen any documentation that it works.

Documented procedures that work all involve defrosting the cryostat. 

Most of these methods are modifications of those used to disinfect
laboratory freezers and the literature is full of those methods. 

1) 95% alcohol. This was primarily shown to be effective for HIV, but is
probably effective against most other organisms. It involves wiping down the
interior of the instrument with 95% alcohol. You can take out just the knife
holder and knife and disinfect those.

Reference: "Frozen section technique for tissues infected by the AIDS
virus". Swisher, BL, and Ewing, EP., Journal of Histotechnology, Vol 9,
No.1, March 1996.

2) 100 percent alcohol is recommended by NACCLS, but they don't give any
documention to support their recommendation. This is also recommended by
Woods and Ellis in their book "Laboratory Histopathology", chap 2, pg 19.

3) Formalin vapor. This involves derfrosting the cryostat and placing a
container of 37% formalin inside overnight. In studies this effectivly kills
organisms in petri dishes. (Shandon, unpublished results. Shandon includes a
formalin method with all their cryostats). Note that this method will not
work in a cold cryostat as the formlin loses its effctiveness at freezing
temperatures.

4) To disinfect for TB you need to use a specialty TB disinfectant to
satisfy your safety officer. Check with them for what type they recommend.
Again, defrosting is necessary.

One way to avoid defrosting is to use a vacuum attachment to suck up debris
before it can conaminate the interior of the cabinet. They you only need to
clean the knife and/or knife holder. I'm sure a certain company out there in
HistoLand can tell you all about that vacuum.

Tim Morken EMT(MSA), HTL(ASCP)
Centers for Disease Control and Prevention
Infectious Disease Pathology
MS-G32 
1600 Clifton Road
Atlanta, GA 30333

PH 404-639-3964
FAX 404-639-3043
email tim9@cdc.gov 

-----Original Message-----
From: Brady, Kimberly [mailto:kbrady@eosbiotech.com]
Sent: Friday, August 03, 2001 4:00 PM
To: 'histonet@pathology.swmed.edu'
Subject: 


Does anyone know of a good disinfectant that can be used to clean a cryostat
while it is cold?  I work in a lab that uses one cryostat to cut both mouse
and human tissue (we just started cutting human tissue) and our cleaning
protocol after cutting human tissue is to turn off the cryostat and to use
commercial bleach.  Unfortunately, some parts look like they are starting to
rust, and it is very time consuming to let the cryostat warm up for
cleaning, then to cool down again for use.  I am new at hist