Rapid detection of Mycobacterium tuberculosis in sputa by the amplification of IS6110

A polymerase chain reaction (PCR) assay for the rapid detection of Mycobacterium tuberculosis in sputum samples was studied. The target DNA was a 123-base pair (bp) fragment of IS6110, which was repeated in the M.tuberculosis genome and was specific for the M.tuberculosis complex. Glass beads (2mm diameter) and lysozyme were used to lyse the mycobacteria and DNA was extracted by the phenol-extraction method. The amplified PCR product was detected by examination of ethidium-bromide-stained agarose gel and by hybridization with an oligonucleotide alkali-phosphatase-labeled probe. A total of 70 samples were tested. PCR was positive in all 13 smear and culture-positive samples, in 5 of 8 smear-negative and culture-positive samples, and in 1 of 49 smear and culture negative samples. The overall sensitivity and specificity were 85.7% and 98%, respectively. Thus, IS6110 as a PCR target was found to be very useful for the rapid diagnosis of M.tuberculosis infection and start of anti-tuberculous chemotherapy.