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Not everything acid fast is Mycobacterium tuberculosis--a case report
E S Olson1, A J Simpson, A J Norton
1Department of Medical Microbiology, St Bartholomew's Hospital, London, UK.
Journal of Clinical Pathology
|November 3, 1998
Summary
The Ziehl-Neelsen stain can misidentify bacteria. Using weaker acid concentrations may cause non-tuberculosis organisms to appear acid-fast, leading to incorrect diagnoses like pulmonary nocardiosis being mistaken for tuberculosis.
Area of Science:
- Microbiology
- Histopathology
Background:
- The Ziehl-Neelsen (ZN) stain is a crucial diagnostic tool for identifying acid-fast organisms, primarily Mycobacterium tuberculosis.
- Histological applications of ZN staining often employ weaker acid concentrations for decolorization.
Observation:
- A patient presented with pulmonary nocardiosis.
- Initial diagnosis based on pleural biopsy using ZN staining suggested tuberculous empyema.
Findings:
- Weaker acid concentrations in ZN staining can cause a broader range of bacteria to exhibit acid-fast properties.
- This can lead to misidentification of acid-fast organisms, as seen in the case of nocardiosis.
Implications:
- The study highlights the potential for misdiagnosis when using modified ZN staining protocols.
- Careful interpretation and consideration of alternative staining methods or clinical context are essential for accurate identification of acid-fast bacteria.