Detection of Mycobacterium leprae DNA in formalin-fixed, paraffin-embedded samples from multibacillary and paucibacillary leprosy patients by polymerase chain reaction.

BACKGROUND: Diagnosis of paucibacillary leprosy is often difficult. A method that could confirm the diagnosis is the polymerase chain reaction (PCR) of M. leprae DNA. This reaction was applied to biopsied tissues of leprotic patients to determine the suitability and sensitivity of the reaction.

METHODS: Biopsy samples were taken from previously untreated patients with multibacillary (5 patients) and paucibacillary (3 patients) leprosy, fixed in formalin, and embedded in paraffin. DNA was extracted from paraffin blocks and PCR applied. The sensitivity of the PCR method was tested by using the serially diluted DNA sample as the template.

RESULTS: All eight patients showed a positive PCR for M. leprae DNA. The sensitivity was such that a single organism of M. leprae, as counted by staining of the acid-fast bacilli was identified by the PCR.

CONCLUSIONS: The PCR method is simple, sensitive, specific, and does not require the use of radioisotopes. It can be applied to the unequivocal diagnosis of paucibacillary leprosy which is difficult by other means. The diagnosis can be obtained within 10 hours.