Cloning of a gene from Mycobacterium tuberculosis coding for a hypothetical 27 kDa protein and its use for the specific PCR identification of these mycobacteria

PCR targeting the IS 6110 has been considered specific for identification of Mycobacterium tuberculosis and is frequently applied to confirm the presence of this organism directly in biological specimens. However, several authors found that some M. tuberculosis strains failed to hybridize with the IS 6110 probe and other authors found that false-positive results may be obtained for clinical samples when some methods based on IS 6110 are used. In the present study, the p27 gene isolated from a cosmid library was found to be highly specific for M. tuberculosis complex strains and allowed us to develop a PCR-based assay for rapid detection and identification of this mycobacterium. One pair of primers and two oligonucleotide probes were successfully used to amplify and to detect the DNA of strains belonging to the M. tuberculosis complex. These primers and probes did not hybridize with DNA from any of the 21 other mycobacterial species tested. It is worth noting that the chosen primers and probes hybridize with DNA from the M. tuberculosis strain with no IS 6110, furthermore no strain without p27 was found among the 410 strains tested in the present study.