Acid-fast stain is used primarily in the identification of pathogenic organisms like the tuberculosis bacillus,
Mycobacterium tuberculosis, and the leprosy microbe, Mycobacterium leprae. In this activity, students perform an acid-fast stain procedure on nonpathogenic cultures of Mycobacterium nonchromogenicum, an acid-fast rod found in soil, and Staphylococcus epidermidis, a nonacid- fast coccus that normally inhabits your skin. In the process, students will learn to use sterile techniques, one of the most crucial components of microbiology.