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Mechanism of acid-fast staining in acid-fast cells and non-acid-fast cell [24] [25] [26] The mechanism of action of the Ziehl-Neelsen stain is not completely understood, but it is thought to involve a chemical reaction between the acidic dyes and the cell walls of the bacteria.
Fungal yeast forms are inconsistently stained with Acid-fast stain which is considered a narrow spectrum stain for fungi. [21] In a study on acid-fastness of fungi, [ 22 ] 60% of blastomyces and 47% of histoplasma showed positive cytoplasmic staining of the yeast-like cells, and Cryptococcus or candida did not stain, and very rare staining was ...
The genus is acid-fast to some degree, it stains only weakly Gram positive. The most common form of human nocardial disease is a slowly progressive pneumonia, the common symptoms of which include cough, dyspnea (shortness of breath), and fever. It is not uncommon for this infection to spread to the pleura or chest wall.
The Kinyoun method can be modified as a weak acid fast stain, which uses 0.5–1.0% sulfuric acid instead of hydrochloric acid.The weak acid fast stain, in addition to staining Mycobacteria, will also stain organisms that are not able to maintain the carbol fuchsin after decolorizing with HCl, such as Nocardia species and Cryptosporidium.
Since MTB retains certain stains even after being treated with acidic solution, it is classified as an acid-fast bacillus. [13] [57] The most common acid-fast staining techniques are the Ziehl–Neelsen stain [59] and the Kinyoun stain, which dye acid-fast bacilli a bright red that stands out against a blue background. [60]
[2] [3] Carbol fuchsin is used as the primary stain dye to detect acid-fast bacteria because it is more soluble in the cells' wall lipids than in the acid alcohol. If the bacteria is acid-fast the bacteria will retain the initial red color of the dye because they are able to resist the destaining by acid alcohol (0.4–1% HCl in 70% EtOH). [4]
Sputum smears and cultures should be done for acid-fast bacilli if the patient is producing sputum. [1] The preferred method for this is fluorescence microscopy (auramine-rhodamine staining), which is more sensitive than conventional Ziehl–Neelsen staining. [4]
The auramine–rhodamine stain (AR), also known as the Truant auramine–rhodamine stain, is a histological technique used to visualize acid-fast bacilli using fluorescence microscopy, notably species in the Mycobacterium genus. [1] Acid-fast organisms display a reddish-yellow fluorescence. [2]