What do acid-fast stains show?

The acid-fast stain is a laboratory test that determines if a sample of tissue, blood, or other body substance is infected with the bacteria that causes tuberculosis (TB) and other illnesses.

How can you tell if a acid-fast stain is positive or negative?

Acid Fast positive cells are stained the pink/red color of carbolfuchsin. Acid Fast negative cells are stained the light blue color of methylene blue.

What color indicates a positive result in the acid-fast stain?

Acid fast stains are used to differentiate acid fast organisms such mycobacteria. Acid fast bacteria have a high content of mycolic acids in their cell walls. Acid fast bacteria will be red, while nonacid fast bacteria will stain blue/green with the counterstain with the Kinyoun stain.

Which diagnosis can be confirmed using the acid-fast stain?

An AFB culture can positively confirm a diagnosis of TB or other infection.

What is the purpose of acid alcohol in acid fast staining?

Acid alcohol has the ability to completely decolorize all non-acid-fast organisms, thus only leaving behind red-colored acid-fast organisms, like M. tuberculosis. The slides are then stained a second time with methylene blue that serves as a counterstain.

Why is carbol fuchsin used in acid fast staining?

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.

What is the purpose of methylene blue in acid fast staining?

After the auramine dye has fully stained the smear, a drop of acid alcohol is applied for one to two minutes to decolorize the smear. Methylene blue or potassium permanganate is used as a counterstain to provide background color.

What is the role of phenol in acid fast staining?

In acid fast stains, the phenol allows the stain to pen- etrate, even after exposure to decolourisors. If an organism is to be termed Acid Fast, it must resist decolourisation by acid-alcohol. A counterstain is then used to emphasise the stained organism.