What is the process of AFB staining? which bacteria known as AFB and why ?

Question

What is the process of AFB staining? which bacteria known as AFB and why ?

Answer 1

AFB staining is simply one of several types of tests used to identify different bacteriae. AFB (Acid Fast Bacteria staining) is used primarily to identify bacteria in the genus Mycobacterium, such as Mycobacterium Tuberculosis. The process includes staining the specimen and then trying to wash out that stain by applying an acid.  If the acid does NOT wash out the color that was applied, then the bacterium is called "acid fast".

Answer 2

Acid-fastness is a physical property of some bacteria referring to their resistance to decolorization by acids during staining procedures.

The high mycolic acid content of certain bacterial cell walls, like those of Mycobacteria, is responsible for the staining pattern of poor absorption followed by high retention.

Very few structures are acid fast, this makes staining for acid-fastness particularly useful in diagnosis:

All Mycobacteria - M.tuberculosis, M.Leprae and atypical Mycobacterium

Nocardia

Head of sperm

Bacterial spores

Cryptosporidium parvum, Isospora and Cyclospora cysts

The normal procedure for Mycobacterium tuberculosis is:

1.Primary Staining: Add Ziehl-Neelsen carbol fuchsin to the slide for 5-10 minutes while applying heat.the heating stage is to make the color to go into the cell wall

2.Follow with a gentle wash with water to cool the slide.

3.Decolorising: Can be done with 20% sulfuric acid and Alcohol separately or with acid alcohol (which contains hydrochloric acid and ethanol). if the bacteri is acid fast it doesn't lose its color in this stage because of its high amouns of lipid

4.Wash the slide in water.

5.Counterstaining: Usually done with methylene blue or malachite green.

The acid-fast bacteria retain the red color, and therefore look hot pink or red. Non acid-fast bacteria will not be red. If methylene blue is used the non-acid-fast organisms will appear blue, and if malachite green is used non-acid-fast organisms will appear green.