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[1] [2] Once stained as part of a sample, these organisms can resist the acid and/or ethanol-based decolorization procedures common in many staining protocols, hence the name acid-fast. [ 2 ] The mechanisms of acid-fastness vary by species although the most well-known example is in the genus Mycobacterium , which includes the species ...
After the Ziehl-Neelsen staining procedure using carbol fuchsin, acid-fast bacteria are observable as vivid red or pink rods set against a blue or green background, depending on the specific counterstain used, such as methylene blue or malachite green, respectively. Non-acid-fast bacteria and other cellular structures will be colored by the ...
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.
Some bacteria have cell walls which are particularly adept at retaining stains. These will appear positive by Gram stain even though they are not closely related to other gram-positive bacteria. These are called acid-fast bacteria, and can only be differentiated from other gram-positive bacteria by special staining procedures. [25]
Other bacteria are commonly identified with a microscope by staining them with Gram stain. However, the mycolic acid in the cell wall of M. tuberculosis does not absorb the stain. Instead, acid-fast stains such as Ziehl–Neelsen stain, or fluorescent stains such as auramine are used. [4]
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.
Gram-positive, nonmotile and acid-fast rods (1-3 μm x 0.2-0.4 μm). Sometimes long rods with occasional beaded or swollen cells having non-acid-fast ovoid bodies at one end. Colony characteristics. Smooth hemispheric colonies, usually off-white or cream colored. May be butyrous, waxy, multilobate and even rosette clustered (dilute inocula).
Mycobacterium leprae is an intracellular, pleomorphic, non-sporing, non-motile, acid-fast, pathogenic bacterium. [3] It is an aerobic bacillus (rod-shaped bacterium) with parallel sides and round ends, surrounded by the characteristic waxy coating of mycolic acid unique to mycobacteria.