Acid fast / Auramine-rhodamine

Author: Nat Pernick, M.D. (see Authors page)

Revised: 23 September 2015, last major update August 2015

Copyright: (c) 2003-2015,, Inc.

PubMed Search: Acid fast[title]
Table of Contents
General | Methods | Micro Images | Videos
  • Ziehl-Neelsen (classic): common method; bacteria stain bright red due to retention of carbol-fuchsin dye; background is methylene blue counterstain; procedure involves heat (#1, #2)
  • Ziehl-Neelsen (modified bleach): may be more sensitive than classic stain (Acta Cytol 2008;52:325,J Cytol 2012;29:165)
  • Ziehl-Neelsen (modified for stool specimens): does not require heating (Centers for Disease Control)
  • Kinyoun: common method; uses more concentrated fuchsin dye and lipid solvent, but no heat; bacteria stain bright red against green background (#1, #2)
  • Fite: to detect M. leprae (leprosy) and Rhodococcus (Diagn Cytopathol 2001;24:244); combines peanut / vegetable oil with xylene to minimize exposure of bacteria cell wall to organic solvents and protect precarious acid-fastness of organism (#1, #2)
  • Ellis and Zabrowarny: protocol excludes phenol; procedure (J Clin Pathol 1993;46:559)
  • Auramine-rhodamine: mixture of Auramine O and Rhodamine B dyes, auramine binds to mycolic acid in cell wall; detection requires a fluorescence microscope (mercury vapor lamp or LED), but is most sensitive stain for mycobacteria (Hum Pathol 1984;15:1085, PLoS One 2011;6:e22495); saves time in searching for microorganisms (Clin Infect Dis 2008;47:203); procedure
  • Water filters are recommended to reduce false positives due to non-TB mycobacteria (Appl Environ Microbiol 2007;73:6296)
  • Micro Images


    Oocysts: modified acid-fast stain

    Stool specimen (Ziehl-Neelsen)

    Oocysts: auramine-rhodamine stain


    Acid-fast stain

    Modified acid-fast stain


    Acid-fast stain

    Mycobacterium tuberculosis:

    Ziehl-Neelsen stains

    Auramine stain of lung

    Skin biopsies

    Mycobacterium avium complex:

    Site-unknown, breast and colon (Ziehl-Neelsen)

    Lymph node post bCG
    vaccination (Ziehl-Neelsen)

    Mycobacterium leprae:

    Liver (Fite stain)


    Fite-Faraco modified acid fast stain of lung


    Nontuberculous mycobacterial infections:
    A: colonic polyp, B: duodenum, C: supraclavicular lymph node

    Tuberculous lymphadenopathy (Ziehl-Neelsen)

    Pleural fluid