Why isn't the Gram stain used on Acid fast bacteria? If you did Gram stain acid-fast bacteria, what would their Gram reaction be? What is the Gram reaction of non-acid-fast bacteria?

Acid fast bacteria are stain by the gram process but it retains the red color like the gram negative. The result will show a false positive to a negative gram bacteria.

Explanation:

The acid fast bacteria are 4 groups of bacteria (Mycobacterium, Nocardia, Corynebacterium, Clostridium) that have the characteristic that they posses a high concentration of micolic acid. This characteristic is sensible to be dye by the gramm process, because the chemicals are not attract among them. To be dye, this kind of bacteria, is necessary used heat and the presence of phenol.