RE: HIV + frozen sections
|From:||"Monson, Frederick C." |
The CDC has passed on the notion that 1% HCHO is equivalent to 1%
paraformaldehyde in its capacity to decontaminate a laboratory surface
(floor) after it has been exposed to HIV. My practice before sectioning
unfixed clinical specimens is to oil the microtome to insure that all the
oil compartments are full of oil with no room for anything else. My
practice when routinely decontaminating following cryosectioning of unfixed
clinical specimens has been to do any of the following.
1. (Draconian Method) Entire MT2 ultramicrotome (plus what
ever else) in a bag (in the fume hood) with 100ml of 20% Formalin in 100%
ethanol (i.e. 8% HCHO in 80% ethanol = final concentrations of effective
agents)(an on-the-fly concoction). Tightly seal the bag, go to Happy Hour
and rest, return in am and remove and dispose of HCHO waste, permit
equipment to dissipate enclosed HCHO until after lunch, then reset equipment
in normal habitat.
2. Just decontaminate the components of cryo system (plus
whatever else) that were exposed in a smaller bag.
3. Wipe with qualified disinfectant. BUT won't get inside
of instruments that may have been contaminated.
I know that HIV probably "dies" when dried, but there are worse
little things that can contaminate your work area and survive 'til you touch
with hand and scratch your nose. PLEASE Note that when paranoid or
justifiably concerned about little bugs, I use Formalin as the source of
HCHO rather than paraformaldehyde. The reason is quite simple. None of us
assays the HCHO we generate from paraformaldehyde (though I shall hear from
her now!) and indeed only assay it by smell in almost every case. Formalin,
on the other hand, is usually a saturated solution of HCHO and is purchased
in a container on which is printed the information concerning concentration,
components and constituents. In decontaminating, I would rather be
absolutely certain about the materials I use. In fixation, 1% HCHO is
probably sufficient to fix most things just fine, and our while assumptions
about the concentration of paraformaldehyde in a 4% suspension of the stuff
may be correct, our assumption about the effective/resultant concentration
of HCHO generated FROM 4% paraformaldehyde is just that, an assumption.
I have taken an entire IEC Minotome from an IEC cryostat, gassed the
chamber and immersed the microtome (20min) in 1% HCHO from Formalin (40%
HCHO = 40g/100ml HOH, thus, 2ml Formalin contains 8g HCHO) (1% HCHO = 0.25ml
Formalin in 50ml ethanol to which is added 49.75 ml of water). While other
rotary microtomes can rust if permitted, the IEC Minotome is better made.
After treatment, I rinse with HOT tap water, turn out the disassembled
microtome on a bench for the night, reassemble and oil in the morning and am
ready to section some 'safe' rodent tissue.
Hope this helps.
Frederick C. Monson, PhD
Center for Advanced Scientific Imaging
Schmucker II Science Center
West Chester University
South Church Street
West Chester, Pennsylvania, USA, 19383
CASI URL: http://darwin/wcupa.edu/casi/
WCUPA URL: http://www.wcupa.edu/
Visitors URL: http://www.wcupa.edu/_visitors/
> From: firstname.lastname@example.org
> Sent: Monday, April 22, 2002 3:33 PM
> To: email@example.com
> Subject: HIV + frozen sections
> Martha Ward writes:
> This question is for folks who are doing direct immunofluorescence on
> renal biopsies. How do you handle decontamintion of the cryostat after
> cutting a known HIV + patient? Our current procedure is to break down
> the cryostat, wipe down with alcohol, emerse the microtome in 100%
> alcohol, soak for 1 hour, allow it to dry overnight in a 40 C incubator
> and put everything back to together the next day. Is there a better way
> of doing this, or is this the way most people handle this? This
> question would also be for routine maintenance of the cryostat, not just
> when we get known infectious sample.
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