Nancy, there are two articles in the literature that I know about that seem
to document TB infection from using a "compressed gas" freezing spray in the
cryostat.

1) "Tuberculosis Infection Associated with Tissue Processing - California"
in: Morbidity and Mortality Weekly Report, Centers for Disease Control and
Prevention, US Public Health Service. Vol 30, No. 6 p.73(Feb 20,
1981)(unfortunately this issue is not available on the CDC web site).
Reported by T. Barret, RN Berkeley and HA Rentein, MD, California State Dept
of Health Services, in the California Morbidity Weekly Report, No. 30, Aug
1, 1980. This report describes a scenario in which two pathologists were
documented to seroconvert against TB antigen three months after doing a
frozen section on a TB-positive patient (baselines on both were negative at
the time the patient was diagnosed). Although 17 employees were in contact
with the patient, only the pathologists seroconverted. And, while only one
of the pathologists was actually present at the autopsy, both were present
at the cryostat when a freezing spray was used to freeze the specimen.
Neither was wearing a mask. It is thought (though not definitively proved)
that the spray action led to the aerosolization of the TB organism and to
infection of the pathologists.

2) "TB Infection from preparation of frozen sections." (Correspondence
Setion) in New England Journal of Medicine, V.305(3)p167, Duray, PH, 1981
(July 16). This is a short letter about a histotech at Norwood Hospital,
Norwood, MA, who seroconverted to TB two months after doing a frozen section
on a TB-positive patient (All employees have annual TB skin tests and this
technologist had been negative). The histotech used a freezing spray to
freeze the specimen. Again, the proof is not definitive, but is suggestive.

Hope this helps!

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: NLOUISEA@aol.com [mailto:NLOUISEA@aol.com]
Sent: Saturday, April 27, 2002 7:18 AM
To: histonet@pathology.swmed.edu
Subject: freezing AFB tissue


Hi all
I understand why NOT to use an aerosol when freezing AFB tissue.  Does
anyone 
know where I can find documentation to support this?  I need to include it
in 
a lab wide safety manual.
Thanks
Nancy