Evaluation of a fluorescence hybridisation assay using peptide nucleic acid probes for identification and differentiation of tuberculous and non-tuberculous mycobacteria in liquid cultures

The performance was evaluated of a fluorescence in situ hybridisation assay using peptide nucleic acid probes (Dako Probe MTB Culture Confirmation Tes t; Dako, Denmark) for identification of Mycobacterium tuberculosis complex (MTC) organisms and differentiation between tuberculous and non-tuberculous mycobacteria (NTM) in material taken directly from Bactec 12B (Becton Dick inson, USA) and MB/ BacT (Organon Teknika, USA) bottles. The test was appli ed to 129 smear-positive (Ziehl-Neelsen stain) clinical specimens, 48 previ ously identified clinical strains of mycobacteria (12 MTC and 36 NTM), and 51 reference strains (7 MTC and 44 NTM) which were all previously inoculate d into Bactec 12B and MB/BacT bottles. The sensitivity and specificity of t he assay for MTC-positive cultures was 87.6% and 100%, respectively, for Ba ctec 12B, and 100%, respectively, for MB/ BacT. The sensitivity and specifi city of the assay for NTM-positive cultures was 100% for both media.