Depending on where the infection may be in your body, your health care provider will collect one of these samples:

• Urine
• Stool
• Sputum
• Bone marrow
• Tissue

The sample is then sent to a laboratory. Some of the sample is placed on a glass slide, stained, and heated. The cells in the sample hold onto the dye. The slide is then washed with an acid solution and a different stain is applied.

Bacteria that hold onto the first dye are considered “acid-fast” because they resist the acid wash. These types of bacteria are associated with TB and other infections.