I  hope it wasn't something I said that makes you feel "very ancient." 
;-)

Anyway, an additional comment on the Leptospira from dog liver. This is
a
very large spirochete, probably one of the largest. If you use this for
your control, and your patient's tissue has syphilis, one of the
smallest
spirochetes, you may end up with a false negative on your patient's
tissue.

The larger Leptospira gets developed first, due to its larger size. The
smaller Treponema (syphilis) needs a longer time in developer, before
it becomes visible. It may take as much as 30 minutes longer in
developer
from the time you first see the Leptospira until the Treponema are
visible. Think of it like an airplane in the air. What can you see
easiest - the Great Wall of China, or the people on the wall?

The same thing can happen if you are using fungus as your control
when you are looking for the much smaller Pneumocystis. Possible
false negative for the patient's P.C.

Moral of the story is . . . always use control micro-organisms that
are comparable in size when doing silver stains.

P.S. I'll be at the Florida Regional meeting this week, and will
be giving a 3 hour workshop on controls on Friday, if you want to hear 
more "exciting" tidbits like this. Hope to meet some Histonetters there!

Peggy A. Wenk, HTL(ASCP)
William Beaumont Hospital
Royal Oak, MI 48073

RSRICHMOND@aol.com wrote:
> 
> Peggy Wenk replies to a question about spirochete and lepra bacilli controls.
> The old Samurai Pathologist feels very ancient - they don't teach this stuff
> in residencies much any more.
> 
> Someone on the list recently suggested a veterinary source for a spirochete
> control - namely Leptospira, and that's what I would go looking for. Dogs die
> of leptospirosis fairly often. The organism is somewhat hazardous in the
> fresh state, not when fixed. Spirochetes in general are not easy to culture,
> and Treponema pallidum, the etiologic agent of syphilis, has never been
> cultured successfully.
> 
> Leprosy requires control tissue containing the etiologic agent of the
> disease, Mycobacterium leprae, which has also never been cultured. It is an
> acid-fast organism, but it does not have the same staining characteristics as
> Mycobacterium tuberculosis, and there is no substitute for it as a control.
> Leprosy affects armadillos, and one leprous armadillo liver would supply a
> universe of histologists with controls.
> 
> Tim Morken at CDC, do you have any leads on this stuff?
> 
> Patient advocates will note that they prefer the term "Hansen's disease" for
> the human disease traditionally called leprosy, but this usage is hard to
> maintain when talking about tissue.
> 
> Bob Richmond
> Samurai Pathologist
> on the road in a motel in Mississippi this morning