The acid-fast bacilli (AFB) stain, also known as the Ziehl-Neelsen stain, is a histological staining technique used to detect the presence of acid-fast bacteria, such as Mycobacterium tuberculosis, which causes tuberculosis. It was developed by German physician Franz Ziehl and German bacteriologist Friedrich Neelsen in 1882.
Under the microscope, acid-fast bacteria will appear as red, rod-shaped structures against a blue or green background.
The AFB stain is commonly used in the diagnosis of tuberculosis and other mycobacterial infections. It is also used in research to study the distribution and localization of acid-fast bacteria in tissues.