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

SETTING: Peptide nucleic acid (PNA) probes designed for specific detection of mycobacteria of the Mycobacterium tuberculosis complex (MTC) and other non-tuberculous mycobacterium species (NTM) are shown to be able to penetrate the mycobacterial cell wall and subsequently hybridize in situ to complementary rRNA. OBJECTIVE: TO demonstrate the use of fluorescein-labelled PNA probes for detection and identification of M. tuberculosis in smear-positive sputum samples. DESIGN: The sensitivity and specificity of the PNA probes were investigated by fluorescence in situ hybridization (FISH) using cultures of mycobacterium strains representing species of the MTC and NTM, respectively. RESULTS: M. tuberculosis strains were detected by FISH using specific fluorescein-labelled PNA probes directly in smear-positive sputum samples without changing the morphology of the cells. CONCLUSION: PNA probes allow for rapid diagnosis of tuberculosis in smear-positive cases.