[Detection and identification of the DNA between Mycobacterium tuberculosis and Mycobacterium nontuberculosis by triplex polymerase chain reaction technique]

Abstract

Objective: To improve the specificity and sensitivity of polymerase chain reaction (PCR) technique for detecting and identification of DNA of M. tuberculosis and M. nontuberculosis.

Method: Three pairs of oligonucleotide primer were used in triplex-PCR. A 383 bp DNA fragment encoding part of the 65,000 mycobacterial surface antigen, a 123 bp fragment corresponding to a specific M. tuberculosis complex sequence which was the insertion sequence 6110 (IS 6110) and a 268 bp fragment for human beta-globin were amplified by triplex-PCR respectively.

Result: The sensitivity of the triplex-PCR-electrophoresis for the DNA of mycobacterium was 0.6 pg. The specific bands of 383 bp and 123 bp among the amplified DNA from M. hominis, M. bovis, BCG and M. simiae were present in the agarose gel. By contrast, only a band of 383 bp was found among the M. nontuberculosis which contained M. avium, M. chelonae, M. scrofulaceum, M. xenopi, M. kansasii, M. intracellulare and M. smegmatis. Compared with the standard strains, there was an additional 268 bp band in simulated clinical samples infected by Mycobacterium. The above 3 specific bands were found neither in other 15 bacterial species tested nor in Mycoplasma pneumoniae. 182 clinical samples were examined by culture, smear and triplex-PCR. 72 nontuberculous clinical samples were all negative. In 110 tuberculosis clinical samples, the positive rates were 2.7%, 13.6% and 32.7%, respectively.

Conclusion: The triplex-PCR possesses a high specificity and sensitivity. This method could detect and identify the DNA of M. tuberculosis and M. nontuberculosis except M. simiae. It is a valuable tool for early diagnosis and differentiation for infection of M. tuberculosis and M. nontuberculosis.