[Histonet] mycobacterium tuberculosis and fixation

Wed Sep 26 16:16:25 CDT 2007

Liz,

Funny you should ask this question. I authored an article in the Dec
2002 HistoLogic entitled "Does Formaldehyde Kill Mycobacterium
tuberculosis?" The article was to some extent a review of the scant body
of literature on this topic. I wrote it because we had a pathologist on
staff who insisted that TB could survive processing and I didn't believe
it. You should be able to find the article at Sakura's website but if
you cannot I may have a pdf of that issue that I can send you or I can
fax it if you send me your fax number. 

The anecdotal reports of TB surviving fixation were typically in autopsy
or embalmed remains. As you can imagine, the first question to consider
is whether the tissue was thoroughly and completely fixed. With autopsy
tissues, organs are often breadloafed and immersed in fixative but if
great care is not exercised, it is not uncommon to see red, apparently
unfixed areas when cutting down organs or viscera if breadloafing was
not adequately done. Embalming is even more tenuous because a number of
factors can affect whether embalming fluid successfully reaches all
tissues of the body.

I don't believe anyone can definitively tell you that TB cannot survive
processing but I am doubtful that there is any reason to be concerned.
I'm aware of no regulatory requirements for the clinical lab pertaining
to the preparation of paraffin sections of TB positive cases. The
presumption is that exposure to formalin and alcohol will neutralize the
organism during the processing cycle. If you are looking for a guarantee
however I'm doubtful anyone can offer you one. 

Conversely we have stringent requirements for the handling of fresh
tissues and frozen sections of unfixed samples when TB is expected.

Histonet is a fairly large community. It will be interesting to see if
anyone can report knowledge of a colleague contracting TB specifically
from exposure to fixed, paraffin processed tissue. I think if there was
any substantial risk we would all be aware of it but I could be wrong.

Vinnie Della Speranza

Manager for Anatomic Pathology Services

165 Ashley Avenue  Suite 309

Charleston, South Carolina 29425

Tel: (843) 792-6353

Fax: (843) 792-8974

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Liz
Chlipala
Sent: Wednesday, September 26, 2007 12:11 PM
To: histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] mycobacterium tuberculosis and fixation

I'm posting this question since I need to research the viability of
mycobaterium tuberculosis in fixed tissue samples.  We quite freqently
handle paraformaldehye fixed samples from guinea pigs and mice that have
been that infected with MTB, after fixation they are stored in 70%
alchol for weeks before I get them.  I have culture data that shows that
these samples that I am receiving have no viable TB present.  I'm
wondering if there is anyone out there that handles fixed TB samples
differently or are they considered non-infectious.  There has been one
published study that did find viable bacteria in autopsy samples that
had been stored in 10% NBF so there is conflicting data.  

Our policy on these type of samples is that we only accept fixed tissue
samples, we do not work with any unfixed tissue samples.  We do make
available for individuals that are grossing in the samples a 3M N95
particulate respirator, wearing the respirator is not manditory and we
have run this procedure past our local OSHA person and they are fine
with it.  

The one concern I have is that we use a shop vac to suck up the paraffin
debris from the microtome and is this causing aerosolization.  Any
comments are appreciated and thanks in advance.

Liz

Elizabeth A. Chlipala, BS, HTL(ASCP)QIHC

Manager

Premier Laboratory, LLC

P.O. Box 18592

Boulder, CO 80308

phone (303) 735-5001

fax (303) 735-3540

HYPERLINK "mailto:liz <@t> premierlab.com"liz <@t> premierlab.com

HYPERLINK "http://www.premierlab.com/"www.premierlab.com

Ship to Address:

Premier Laboratory, LLC

University of Colorado at Boulder

MCDB, Room A3B40

Boulder, CO 80309

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