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[Molecular pathologic detection of mycobacteria]
D R Zimmermann1, R Städeli-Brodbeck, M Ajmo
1Departement Pathologie, Universität Zürich.
Verhandlungen Der Deutschen Gesellschaft Fur Pathologie
|January 1, 1997
Summary
Detecting mycobacterial DNA in formalin-fixed tissues is challenging due to degradation. Optimized polymerase chain reaction (PCR) assays targeting small DNA fragments improve the diagnosis of mycobacterial infections in these samples.
Area of Science:
- Microbiology
- Molecular Biology
- Pathology
Background:
- Direct pathogen detection methods like PCR and TMA have advanced mycobacterial infection diagnosis.
- Standard protocols are optimized for fresh specimens, but formalin-fixed tissues present challenges due to nucleic acid degradation.
Purpose of the Study:
- To adapt and evaluate PCR assays for detecting Mycobacterium tuberculosis complex DNA in formalin-fixed, paraffin-embedded tissues.
- To improve the diagnostic yield of mycobacterial infections in routinely processed biopsies.
Main Methods:
- Developed PCR assays with small amplification targets (< 200 bp) for IS6110 and 65 kDa-antigen genes.
- Applied these assays to formalin-fixed, paraffin-embedded tissues with suspicious lesions and negative Ziehl-Neelson stains.
- Incorporated a third PCR assay with sequencing for M. leprae and atypical mycobacteria detection.
Main Results:
- Successfully detected M. tuberculosis complex DNA in approximately 25% of tissues with granulomatous inflammation and negative Ziehl-Neelson stains.
- Assay sensitivity was influenced by the extent of DNA degradation.
- The PCR approach significantly supplemented conventional histological examination.
Conclusions:
- Optimized, short-amplicon PCR assays are effective for diagnosing mycobacterial infections in formalin-fixed, paraffin-embedded tissues.
- This molecular method enhances diagnostic capabilities where traditional methods may fail due to sample degradation.