Ziehl-Neelsen (ZN) staining: 8 organisms and 10 steps

Ziehl-Neelsen (ZN) staining is a specific bacteriological stain used to identify acid fast organisms.

8 Organisms that stain with Ziehl-Neelsen Procedure

1. Mycobacterium tuberculosis and M. leprae
2. Mycobacterium avium intracellulare (atypical)
3. Nocardia spp.
4. Rhodococcus spp.
5. Legionella micdadei
6. Schistosoma spp. (cortical spines)
7. Echinococcus spp. (hooklets)
8. Protozoa – Cryptococcus spp.

ZN staining is a simple staining process. It can be easily done as an outpatient procedure. Here are the 10 steps of this procedure

1. Prepare smear
2. Allow it to air dry and fix with gentle hit
3. Add carbolfuschin
4. Heat it to steaming for 3-5 minutes
5. Allow it to stand for 5 minutes
6. Wash in running tap water
7. Decolorize with Acid Fast Decolorizer for 2 minutes or until no more stain comes off in washings
8. Wash with water
9. Counterstain with Methylene blue
10. Wash, dry and examine under oil immersion objective.

If the stain is red at the end of procedure, the test is positive. While if, the organism stains blue, the test is negative

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References

1. Ziehl-Neelsen Stain – ScienceDirect
2. First Aid for USMLE Step 1