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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.
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.
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 ...
Acid fast (Ziehl-Neelsen technique) Film stained with hot Z.N.C.F. decolourised (acid-alcohol) and counter stain with methylene blue Separate non-decolorized acid fast bacteria that are not decolorized from colorized non-acid fast bacteria Acid fast bacteria:Red Non acid fast: Blue 5 Endospore (Dornor's method)
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).
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]
Since this genus has cell walls with a waxy lipid-rich outer layer containing high concentrations of mycolic acid, [4] acid-fast staining is used to emphasize their resistance to acids, compared to other cell types. [5] Mycobacterial species are generally aerobic, non-motile, and capable of growing with minimal nutrition.
Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. [1] Their defining characteristic is their cell envelope , which consists of a thin peptidoglycan cell wall sandwiched between an inner ( cytoplasmic ) membrane and an ...