[Histonet] GMS Question

[Goins, Tresa]

Hi Gayle -

We have never had a "noticeable" problem detecting fungi using 5% aqueous chromic acid at room temperature for 1 hr.  The presence of mature and immature wall structures may be the reason. We have never tried to determine the "end point" for over oxidation, but my best guess is that it is much longer than 60 minutes.  

More often, I think a false negative would result from inadequate oxidation of the fungal cell wall. 
In addition to cell wall maturity, I believe the composition adds to differences in rates of oxidation, the major contributors being the prevalence of precursors susceptible to aldehyde formation and melanin.  One needs enough product to produce a visible color reaction.

A complex question and any more detail and I will have to hit the books.

Tresa




-----Original Message-----
From: Gayle Callis [mailto:gayle.callis at bresnan.net] 
Sent: Friday, May 01, 2015 1:17 PM
To: Goins, Tresa; histonet at lists.utsouthwestern.edu
Subject: RE: [Histonet] GMS Question

Hi Tresa, 

What staining parameters do you suggest for seeing  mature and/or immature
fungal cell walls?   I don't think you will know what level of maturity is
present before doing a fungus stain.  But wouldn't both levels of maturity
both be present if the fungus is actively growing in a tissue?      

What do you recommend, using both a PAS, or chromic acid/Schiffs along with
chromic acid GMS method?   

We used 4% chromic acid at RT for 1 hour but would you recommend duplicating slides so you do pull one slide out of chromic acid at 30 minutes and one for 60 minutes to stain either mature or immature fungal and/or both cell
wall structure.   

Gayle Callis
HTL/HT/MT (ASCP) 

    

-----Original Message-----
From: Goins, Tresa [mailto:TGoins at mt.gov]
Sent: Friday, May 01, 2015 11:29 AM
To: Paula Lucas; histonet at lists.utsouthwestern.edu
Subject: Re: [Histonet] GMS Question

To get a positive PAS or GMS fungal stain, one must oxidize the carbohydrate in the fungal cell wall.  
Chromic acid is a stronger oxidizer than periodic acid, so would work better with mature fungal cell walls that are highly polymerized.
Treat an immature cell wall for too long, and you may get a false negative because the carbohydrate structure no longer resembles a fungal cell wall.

Tresa

-----Original Message-----
From: Paula Lucas [mailto:plucas at biopath.org]
Sent: Friday, May 01, 2015 8:17 AM
To: histonet at lists.utsouthwestern.edu
Subject: [Histonet] GMS Question

Hello,

 

I think I already know the answer but I'm not sure why so if someone can help me understand the theory behind it, I would greatly appreciate it.

 

Currently, we use the Richard Allen kit for the GMS stain and it uses Periodic Acid as the 1st step.  

We use a control tissue from a case we had that was positive for fungus and it's a fungus ball from the Rt Maxillary. 

We ran a test for fungus on a different and current case of the same tissue (different patient): Rt Maxillary sinus.

 

The control tissue did work, but the patient's tissue did not, so the doctor ordered a PAS for fungus and this clearly showed the fungal elements nicely.


 

My question is why would the control and patient tissue have different results when they are both fungus balls from the same specimen source?

 

Thanks in advance,

Paula

Lab Manager

Bio-Path Medical Group

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