[Histonet] How to eliminate AFB contamination on slides?

Vinnie Della Speranza dellav <@t> musc.edu
Wed Apr 6 14:15:41 CDT 2005

this can be a complex problem to resolve.

acid fast organisms are environmental bugs and frequently contaminate water systems. we have lots of acid fast bugs in the tap water here.

this means that your tissue float baths could have afb floating around in them, which can account for bugs being found on the glass surrounding sections that don't have the accompanying histologic features suggested of acid fast infection. don't believe me? it happened here and took so sleuthing to figure our where the contamination was coming from.

we clean all tissue floats with bleach daily and allow to air dry after use.

at another facility, we had a Millipore de-ionizing system with a 30 gallon wall mounted holding tank. the holding tank became contaminated with AFB which was a bit of a headache to clean. once again, changing out filters according to manufacturers recommendations is critical to avoiding this problem

you will need to use ultra-filtered water using  a sub-micron particle filter. be sure to change out these filters regularly as organisms can get past the filter once the filter becomes saturated.

don't bother using sterile water. you have no assurance that bugs are not present in sterile water, just that they are non-viable.

your carbol fuchsin stain solution can become contaminated from very positive control sections. it is important that slides are NOT immersed into a coplin jar of carbol fuchsin that you intend to re-use. slides should be stained horizontally, flooding the slides individually with stain. as has already been stated by others, do NOT place patient section onto the same slide as your positive control to avoid cross contamination

good luck in resolving your problem

Vinnie Della Speranza
Manager for Anatomic Pathology Services
Medical University of South Carolina
165 Ashley Avenue  Suite 309
Charleston, SC 29425
Ph: 843-792-6353
fax: 843-792-8974

>>> <Heather.A.Harper <@t> pcola.med.navy.mil> 04/06/05 01:34PM >>>
We are having problems with the AFB stain. Almost everything we do AFB
stains on has extracellular "AFB positive organisms" without an associated
tissue response. Do we need to change our stain or use better grade water?
Anybody who has any ideas or suggestions or has had this problem in the
past, let me know what you did to correct the problem. Thank you to all in


Heather A. Harper

Supervisor of Histology/Morgue

Naval Hospital of Pensacola, FL

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