Magnified 1000X, this fluorescent acid-fast stained (Smithwick) photomicrograh revealed the presence of Mycobacterium tuberculosis bacteria in a sputum smear. M. tuberculosis is an acid-fast bacterium (AFB), and is therefore, undetectable when stained using a Gram stain technique. However, using the Smithwick method, which employs acridine orange as the specific stain, the M. tuberculosis bacteria glow yellow under ultraviolet light microscopy.
Source: CDC/ Ronald W. Smithwick
