Comparison of DNA targets for amplification by polymerase chain reaction for detection of Mycobacterium tuberculosis in sputum.

PCR assays for detection of Mycobacterium tuberculosis were compared using three different primer pairs to amplify fragments of IS 6110, pab and mtp 40 genes. The amplified products were detected by gel electrophoresis. The detection limit of PCR assay for amplification of IS 6110, pab and mtp 40 genes was 10,100 and 100 femtograms of purified M. tuberculosis DNA, respectively. Fifty-six smear-positive sputum samples were tested for the sensitivity of detection. Two sputum specimens contained inhibitors that were not removed after treatment. Of 54 specimens, 53 was positive for M. tuberculosis and one was positive for mycobacteria other than Mycobacterium tuberculosis (MOTT) by culture method. The one that grew MOTT was PCR-negative. Of 53 culture-positive found to contain M. tuberculosis, amplified products were detected in 47 (90%), 28 (53%) and 17 (30%) samples in which the target for amplification was IS 6110, pab and mtp 40 genes, respectively. This study confirms the potential of IS 6110 amplification by polymerase chain reaction for rapid detection of M. tuberculosis in clinical specimens.