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

ac′id-fast′ness n.


(Microbiology) (of bacteria and tissues) resistant to decolorization by mineral acids after staining


resistant to decolorizing by acidified alcohol after staining.
ac′id-fast`ness, n.
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"
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References in periodicals archive ?
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.