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Blasto. hominis - question for Judy D.

JEDilworth bactitech at nospamhortonsbay.com
Wed Jul 3 09:40:38 EST 2002

I am crossposting your excellent information to bionet.parasitology.
This is the newsgroup where the question regarding B. hominis

Judy Dilworth, M.T. (ASCP)

Michael Corriss wrote:
> Delurking:
> I really should put in my 2 cents or more.
> _Blastocystis hominis_ is a rather plesiomorphic critter. I've seen them
> ranging in size from smaller than a microcytic RBC to larger than _E.
> histolytica_, with no vacuoles or six and one to four nucleoid bodies.
> The large vacuole form is the one I usually note when scanning slides
> (Wright-Giemsa stained air-dried stool smears - looking for WBCs - I
> work Hematology). The large vacuole and multiple nuclei in the
> Tri-chrome aid in identification. The small cysts with insignificant
> vacuole may be easily overlooked among all the debris in the
> heterogenous material that can be stool. I've noted my Pathologists
> hesitant to verify identity if it isn't "textbook" in form. Recognition
> is, of course, related to experience and may be easily overlooked since
> they are so rather non-descript.
> I invite you to see small pictures of such organisms. They will be
> replaced with larger, clearer photos soon as well as regularly stained
> parasite photos:
> http://www.mcorriss.com/PB1.html
> Go to bottom of page to navigate to other sections - the ticks thumbnail
> 'll bring you to the microscopic page.
> ( I'm working on the new web site and have plenty of memory now but the
> core lab is understaffed and someone's always sick or on vacation or
> something and I suppose soon I'll be permitted to use some of my 300+
> hours of vacation time and update my new site ;-) . ) I intend to add
> crystals and more parasites and other microscopic "stuff" as well as
> text, soon.
> _B. hominis_ historically has been taught as an incidental commensal
> more indicative of poor housekeeping than disease; the volume of
> pathology associated is low, and as such has generated little interest
> and research. The literature is much less than most of the other
> intestinal parasites. Still, there's ongoing research. About 4-5 years
> ago a paper was published "A parasite finds a home" or something like
> that in either _Nature_ or _Science_. (I'll look around - I know it's in
> one of the multitudes of paper piles I have.) After a cladistic analysis
> of its genome it placed among stramenopiles (diatoms, brown algae,
> xanthophytes, chrysophytes, oomycetes, and labyrinthulids) closely
> related to brown algae. The textbooks always placed it as an amoeboid or
> aberrant fungal body. I used to think they were a degenerate flagellate
> due to certain staining characteristics and was surprised when a patient
> didn't respond to Flagyl. Papers have been published attributing
> treatment efficacy to metronidazole, iodoquinol, and also to
> trimethoprim-sulfamethazole. But the placement as near-brownalga may
> cast some doubt about standard treatments and a novel compound may be
> required.
> It took me several years to convince the pathologists that the scant
> plain giemsa stained round body found (no vacuole) was actually a
> parasite -_Blastocystis_ until a couple of patients presented with such
> high titres that all morphologies were present under the same oil
> immersion field! Still the consensus in the medical community is
> doubtful about the pathology. Koch's postulates haven't ever been
> fulfilled and proper controlled studies are missing in the literature.
> Isolated reports associate high titres with illness (seen reports of >5
> and >10 /lpf) but without proper studies, they are "Just So" stories.
> I'm certain that there are cases where _B. hominis_ is the culprit in
> disease with chronic diarrhea, flatulence, and cramps and no good way of
> eliminating the organism. It's under-reported and under-appreciated as a
> vector of disease.
> I'd like to suggest to any and all US techs involved with intestinal
> parasites to get a free CD from CDC called DPDx Identification and
> Diagnosis of Parasites of Public Health Concern
> http://www.dpd.cdc.gov/dpdx
> It's really neat. The CD is essentially the website so those from other
> countries may get all the same data from the web site. Who knows, they
> may even send the CD to health care professionals from elsewhere,
> inquire.
> I'm not a physician so take everything I said with a shaker of salt.
> Back to lurk mode.
> -mpc
> Michael Patrick Corriss AB-Biol (NYU), HT (ASCP)
> http://www.mcorriss.com

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