Table 3.

Commonly used stains for detection of acid fast bacilli.

Stain	Specimen type	Appearance	Other Findings	Mycobacteria
Ziehl-Neelson [121]	Any clinical specimen	Bright red with blue background		All
Modified Kinyoun [121]	Cytospin or solid culture media	Bright red	Weakly acid fast organisms do not appear bright red	M. fortuitum M. chelonae M. abscessus
			All organisms appear identical with variable staining	MAC
			Filament-like or with slight branching	Dry colonies of MAC
Rapid Modified Auramine O Fluorescent [122]	Any clinical specimen	Yellow to orange or bright green with dark background	Some rapid growing mycobacteria may not fluoresce well	All
Fite [123]	Preferred for tissue specimens	Pink with blue background		Preferred stain for M. leprae
Gomori-methenamine Silver Stain [124]	AFB in tissue specimens	Brown to black		M. kansasii MAC
Periodic Acid Schiff Stain [124]	AFB in tissue specimens	Pink		M. ulcerans M. chelonei M. kansasii MAC from skin

*Reduced with formalin.

Abbreviations: AFB – Acid Fast Bacilli, MAC – Mycobacterium Avium Complex.