A sputum stain for Mycobacteria is a laboratory test performed on a sample of your sputum, or phlegm. It’s also known as an acid-fast bacillus (AFB) stain or a tuberculosis (TB) smear. A doctor ...
Health on MSN

What causes brown mucus?

Medically reviewed by Amelia MacIntyre, DO Smoking can lead to brown mucus due to tar build-up in the lungs. Inhaling pollutants and toxins can cause brown mucus. Lung infections from bacteria and ...