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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 cytological sample of the liver obtained through a fine needle aspirate revealed intracellular acid-fast bacilli identified as Mycobacterium avium.
Non-tuberculous mycobacteria (NTM) are acid-fast bacteria categorized into rapidly growing and slow growing mycobacteria.
The woman's sputum had >100 acid-fast bacilli and was culture positive for a Mycobacterium tuberculosis strain exhibiting resistance to isoniazid, rifampin, fluoroquinolones (low-level resistance), ethambutol, ethionamide, and aminoglycoside but susceptibility to cycloserine, PAS, bedaquiline, and linezolid.
The chances of acid-fast bacilli (AFB) identification in tissue section are less because xylene and formalin affect the sensitivity of Ziehl-Neelsen (ZN) method to detect Mycobacterium tuberculosis in histopathology sections.
Comparison of fluorescence microscopy with Ziehl-Neelsen stain for demonstration of acid-fast bacilli in smear preparations and tissue sections.
All cases fulfilled the clinical criteria according to Chinese Society of Gastroenterology :[sup][5] (1) histological biopsy showed epithelioid granuloma with caseous necrosis in intestinal tissue or mesenteric lymph nodes; (2) intestinal tissue biopsy was positive for MTB on culture or acid-fast stain; (3) patients showed a good response to anti-TB therapy with clinical manifestation consistent with active TB.
Upon detection of nodules in the tissue, tissue smears were stained using a commercial kit (TB Quick Stain, Becton Dickinson, Franklin Lakes, New Jersey) specifically for acid-fast bacteria.
No acid-fast bacilli (AFB) were visualised on Fite staining (Figure 1).
Slit skin smear examination from six sites (right and left ear lobules, right and left sides of nose, and from any two lesions) revealed positive findings for acid-fast bacilli with bacteriological index of 2.
The Food and Drug Administration (FDA) has cleared the Xpert MTB/RIF Assay (Cepheid; Sunnyvale, California) with an expanded intended use that includes testing of either one or two sputum specimens as an alternative to examination of serial acid-fast stained sputum smears to aid in the decision of whether continued airborne infection isolation (All) is warranted for patients with suspected pulmonary tuberculosis (1).