Detection of Mycobacterium leprae by Nested PCR Targeting M. leprae-Specific Repetitive Element (RLEP) Sequence

The aim of this work was to validate a rapid and an accurate method for detecting Mycobacterium leprae in clinical specimens using nested PCR targeting M. leprae-specific repetitive element (RLEP) sequence. The primers were derived from the RLEP sequence which yield a 272 bp outer product and a 230 bp inner product. The specificity and the sensitivity of the nested PCR were compared with those of single PCR for detecting M. leprae using DNAs isolated from reference strain and various species of Mycobacterium. The results showed that the sensitivity of the nested PCR was about 100 to 1,000 times higher than that of the single PCR and also showed that both the single and the nested PCR were highly specific to M. leprae. Subsequently, the usefulness of the single and nested PCR was evaluated with clinical samples isolated from leprosy patients. The number of positive detections by the single and the nested PCR with a total of 20 specimens from leprosy patients were 9 (45%) and 20 (100%), respectively. The results clearly showed that nested PCR has highest sensitivity in detecting M. leprae from clinical specimens. Therefore, nested primers targeting RLEP sequence developed in this study seems to be useful to detect the presence of M. leprae.