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These acid-fast organisms like Mycobacterium contain large amounts of lipid substances within their cell walls called mycolic acids. These acids resist staining by ordinary methods such as a Gram stain. [9] It can also be used to stain a few other bacteria, such as Nocardia. The reagents used for Ziehl–Neelsen staining are carbol fuchsin ...
Very few structures are acid-fast; this makes staining for acid-fastness particularly useful in diagnosis. The following are notable examples of structures which are acid-fast or modified acid-fast: All Mycobacteria – M. tuberculosis, M. leprae, M. smegmatis and atypical mycobacteria.
Mycobacterium tuberculosis (M. tb), also known as Koch's bacillus, is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. [1] [2] First discovered in 1882 by Robert Koch, M. tuberculosis has an unusual, waxy coating on its cell surface primarily due to the presence of mycolic acid.
It is Gram-positive by Gram staining, but Mycobacterium leprae was traditionally stained with carbol fuchsin in the Ziehl–Neelsen stain. Because the bacilli are less acid-fast than Mycobacterium tuberculosis (MTB), the Fite-Faraco staining method, which has a lower acid concentration, is used now. [9] [10] In size and shape, it closely ...
The two most common methods for visualizing these acid-fast bacilli as bright red against a blue background are the Ziehl-Neelsen stain and modified Kinyoun stain. Fite's stain is used to color M. leprae cells as pink against a blue background. Rapid Modified Auramine O Fluorescent staining has specific binding to slowly-growing mycobacteria ...
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]
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.
The term "fast growing" is a reference to a growth rate of 3 or 4 days, when compared to other Mycobacteria that may take weeks to grow out on laboratory media. Pulmonary infections of M. fortuitum are uncommon, but Mycobacterium fortuitum can cause local skin disease, osteomyelitis (inflammation of the bone), joint infections and infections of ...