The bacteria stain Gram-positive, acid-fast. The cell wall contains as high as 60% lipid, giving the mycobacteria their hydrophobic characteristics, slow growth and resistance to desiccation, disinfectants, acids and antibodies. ("Mycobacterium" Family). They are not easy to stain with analine dyes; although they are Gram positive it may not be easy to confirm this. Ziehl-Neelsen staining results in stain pink with hot carbol fuscin and then resist decolourisation with 3 percent hydrochloric acid in 95% alcohol (i.e. they are acid-alcohol fast); following washing, the slide is counterstained with e.g. methylene blue.