PCR to detect Mycobacterium tuberculosis DNA in sputum samples from treated leprosy patients with putative tuberculosis.

In this study of leprosy patients with putative tuberculosis, the polymerase chain reaction (PCR), one of the most reliable and sensitive molecular diagnostic methods, was carried out for the specific detection of Mycobacterium tuberculosis DNA. Sputum samples from 43 patients at Baba Baghi Leprosarium in Iran were tested. The DNA extraction method was based on the lysing and nuclease-inactivating properties of guanidinium thiocyanate (GuSCN) together with the nucleic acid binding properties of diatoms or silica particles. Primers for a 123-base pair (bp) fragment of the repetitive DNA sequence of M. tuberculosis were used for the PCR assay. The results of PCR were compared with direct microscopy and culture. In total, 14% of the patients in this study were found to be PCR positive for M. tuberculosis. No positive results were found by direct microscopy for acid fast bacilli (AFB) and culture. It was thought probable that the positive PCR results indicated the tuberculosis (TB) in such treated leprosy patients.