Acridine orange is a fluorochrome that binds to nucleic acids. Method is used for detecting low numbers of
organisms in cerebral spinal fluid, blood, buffy coat preparations from neonates, and tissue specimens. The stain
maybe useful in interpreting purulent specimens that failed to give clear results with the Gram stain. Other
microorganisms are well stained with this method: Mycoplasma, Pneumocystis, Borrelia, Acanthamoeba,
0.2 M sodium acetate buffer (pH 3.75). Add Acridine orange to buffer
1. Dry then fix the smear in methanol for 2 minutes.
2. Stain with Acridine orange for 1 minute.
3. Rinse with distilled water.
Bacteria and yeasts stain bright orange/red, and tissue cells stain black to
1. Emanuel Goldman and Lorrence H. Green (ed.): Practical handbook of microbiology, 2009, 39-40.
Blood cells are not fluorescent; the stain can be useful for screening blood cultures for the growth of
(c) Costin Stoica