Re: [Histonet] False positive AFB

From:"Claye Clyatt"


Would it not be wise to identify AFB contamination in one's water
source?  If contamination is present, I think it could be assumed that
AFB contamination could also enter the specimen by fixation and
processing in house made 10% formalin, alcohol dilutions, etc.  I
routinely culture our deionized water once a month.  Not being a
microbiologist, I'm not sure if I'm eliminating the possibility of AFB
contamination by only routine culture.  Do I need to request an AFB


Claye Clyatt
Chief Histotechnologist
Department of Pathology 
Room #BF119
Medical College of Georgia
Augusta, Ga 30912
office   (706) 721-3630
pager  (706) 721-7243-1132

>>>  12/11/03 08:57AM >>>

From personal experience I do know that acid fast organisms are present
some tap water.  We cultured them from water after some bad experiences
false positives.  Wang reported that somewhere over 30% of water
fountains showed 
the presence of acid fast organisms (non-pathogens, but who can tell
difference on a stained slide).  This was done using the fluorescence
As a consequence, we filtered our water bath water through a Millipore
after it was already passed through a charcoal filter and a deionizing
 We also used no tap water prior to the carbol-fuchsin and we ran a
control (uterus - extra cuts from blocks as the routine H&Es were cut) 
the same days workload with each batch of AFB slides.   So take care
with your 
AFB stains.

Freida Carson

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