You must never assume that water is clean just because it come packaged
clean or arrives through a purification system.  We use very
sophisticated water purifiers in our manufacturing process but were not
able to completely remove organisms until we added ultra fine filters at
the end of the purification process.  UV and Deionization systems will
kill bacteria and remove minerals but will not remove dead bacteria.
Only filters will do that.  Also, unless you have a UV loop where the
water is constantly moving, bacteria will grow even in a UV system.
Prepackaged water is only clean until you open the package.  Then it is
only as clean as the rest of your lab. 

Best to all,

Cliff Berger
Decal Chemical Corp.
www.decal-bone.com



-----Original Message-----
From: FreidaC@aol.com [mailto:FreidaC@aol.com] 
Sent: Friday, January 04, 2002 10:04 AM
To: histonet@pathology.swmed.edu
Subject: AFB contamination


Water is probably the number one cause of false positive AFB stains.  We
had 
a horrible problem with it many years ago.  Acid-fast organisms have
been 
reported growing (well present at least) in 40 gal formalin tanks, in
the old 
Tissue Mat paraffin wafers and in a tremendous number (over 30 %) of
water 
fountains.  We even found AFB in our gelatin that we used in the water
bath. 
This is all information from published papers.  While many of the
organisms 
may not be pathogens, they are acid fast.  We finally went to Millipore 
filtered water, that had already been through a charcoal filter and 
deionizing column, for water baths and for all water changes before the 
carbol fuchsin stain.  We did use staining jars but filter the reagent
each 
time.  I strongly recommend a negative control cut from a case processed
the 
same day as the requested AFB tissue.  We always picked up extra
sections 
from a hysterectomy case and ran them along with the stain.  If there is
any 
doubt about contamination, the negative controls are very, very
carefully 
examined.  Using this type of negative control (from the same day's
workload) 
checks for contamination at every step of the procedure.

Freida Carson