Re: [Histonet] H. pylori


Don't know if this would apply to IHC on bacteria but . . . any chance that
some of the bacteria are dead or dying?

If they are dead or dying, the cell wall has been compromised. I know that
this interferes with the Gram stain, causing Gram + not to retain the
blue/black color, and subsequently staining with the red dye, making it look
like a Gram - bacteria. Romanowsky type stains (Giemsa, Diff Quik, etc.) may
not stain the bacteria at all.

We see this on specimens that have too many microorganisms (where crowding
causes a competition for nutrients and some die) or where the patient has
started a treatment (antibiotic, Peptobismo, etc.) and some of the bacteria
are dying.

If the cell wall is being compromised in some of the bacteria, maybe the
"number" of antigen sites are fewer in these compromised bacteria than in
the non-compromised bacteria. So what you are seeing may be due to a
difference in antibody-antigen binding sites, and thus a difference in
staining intensity.

Maybe try a Gram stain (Brown & Hopps, for example) or a Giemsa/Diff-Quik,
so see if there is cell wall compromising going on.

I'm not an expert on IHC. Just a thought.

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

----- Original Message -----
From: "Angela Bitting" 
Sent: Tuesday, October 12, 2004 7:40 AM
Subject: [Histonet] H. pylori

> We're perplexed. We've been using Dako's H. pylori AB with Proteinase K
> antigen retreival for years now and have never had this problem. Our
> control is teeming with organisms but some are staining brown and others
> are more of a bluish color. I'm sure they are all H. Pyl organisms, but
> I can't figure out why they aren't all staining the same.
> Dako says they haven't had any complaints about their Lot number. We've
> tried different vials from that same Lot # and both act the same.
> Trying different dilutions didn't help. Now, we're extending the
> Proteinase K time. After this, we're out of ideas.
> Help!
> Angela Bitting, HT(ASCP)
> Technical Specialist, Histology
> Geisinger Medical Center 23-00
> 100 N Academy Ave.
> Danville, PA 17822
> phone  570-214-9634
> fax  570-271-5916
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