Detection of Mycobacterium leprae DNA chain reaction in the blood of individuals, eight years after completion of anti-leprosy therapy

Thirty eight patients with indeterminate leprosy (HI), at least 4 to 6 year s after discharge from multibacillary (MB) or paucibacillary (PB) schemes o f anti leprosy multidrug therapy (MDT), were submitted to traditional diagn ostic procedures for leprosy and to polymerase chain reaction (PCR) analysi s of different clinical samples for detection of Mycobacterium leprae DNA. No significant difference was observed for any of the parameters analyzed b etween PB or MB schemes of treatment and no indications were found for more efficient outcome of HI using the MB scheme. Remarkably, 18 (54.5%) of the individuals were PCR positive in at least one of the samples: positivity o f PCR was highest in blood samples and four individuals were PCR positive i n blood and some other sample. Upon comparison of PCR results with clinical and histopathological parameters, no correlation was found between PCR-pos itivity and eventual relapse. This is the first report on detection of M. l eprae DNA in PB patients, more than half a decade after completion of MDT s uggesting that live bacilli are present and circulating much longer than ex pected, although reinfection of the individuals can not be excluded. Overal l, we feel that because of the high sensitivity of the assay, extreme care should be taken about association of PCR results, efficacy of treatment and disease status.