Direct detection and identification of Mycobacterium tuberculosis in smear-positive sputum samples by fluorescence in situ hybridization (FISH) usingpeptide nucleic acid (PNA) probes

SETTING: Peptide nucleic acid (PNA) probes designed for specific detection of mycobacteria of the Mycobacterium tuberculosis complex (MTC) and other n on-tuberculous mycobacterium species (NTM) are shown to be able to penetrat e the mycobacterial cell wall and subsequently hybridize in situ to complem entary rRNA. OBJECTIVE: TO demonstrate the use of fluorescein-labelled PNA probes for de tection and identification of M. tuberculosis in smear-positive sputum samp les. DESIGN: The sensitivity and specificity of the PNA probes were investigated by fluorescence in situ hybridization (FISH) using cultures of mycobacteri um strains representing species of the MTC and NTM, respectively. RESULTS: M. tuberculosis strains were detected by FISH using specific fluor escein-labelled PNA probes directly in smear-positive sputum samples withou t changing the morphology of the cells. CONCLUSION: PNA probes allow for rapid diagnosis of tuberculosis in smear-p ositive cases.