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Not decolorized by acid after staining, as bacteria that retain dye after an acid rinse.

ac′id-fast′ness n.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Microbiology) (of bacteria and tissues) resistant to decolorization by mineral acids after staining
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014


resistant to decolorizing by acidified alcohol after staining.
ac′id-fast`ness, n.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Adj.1.acid-fast - not easily decolorized by acid solutions; pertains to micro-organisms (especially the tubercle bacillus that causes tuberculosis)
imperviable, impervious - not admitting of passage or capable of being affected; "a material impervious to water"; "someone impervious to argument"
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
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A commercial veterinary laboratory (IDEXX Laboratories) isolated an acid-fast organism from the lung swab.
We believe that the identified acid-fast organism named "M.
The acid-fast organism that was isolated was identified as MTBC by the AccuProbe TB assay (GenProbe Inc., San Diego, CA).
Extensive systemic checkup, including bronchoscopy, bronchoalveolar lavage (BAL) with CD4/CD8 ratio evaluation, and transbronchial biopsy, revealed no evidence of acid-fast organisms. Transbronchial biopsy showed noncaseating granulomatous inflammation, typical for sarcoidosis.
At 1 month follow-up, 1 sputum sample was negative for acid-fast organisms, and 1 BAL specimen was positive by microscopy and in culture.
Testing for acid-fast organisms in ascitic fluid is frequently negative in patients with abdominal TB, with 3% being positive in TB peritonitis [6].
No Reed-Sternberg cells, acid-fast organisms, fungi, parasites, or foreign material were identified, and mitoses were sparse.
Acid-fast smears are a necessary first step but are neither specific nor sensitive; mycobacteria can be differentiated from other acid-fast organisms such as nocardia, but definitive discrimination of M.
Special staining for acid-fast organisms and fungi had been negative.