Equal rates of drug resistance in leprosy cases with relapse and recurrent/chronic Type 2 reaction: time to revise the guidelines for drug-resistance testing in leprosy?

BACKGROUND Leprosy relapse/recurrence is a serious concern particularly in a leprosy-endemic nation such as India. It is believed that bacilli persisting even after multidrug therapy can cause relapse; recently, however, drug resistance as a cause for recurrences and chronic erythema nodosum leprosum (ENL) has been speculated. AIM To study drug-resistance patterns in cases of leprosy relapse and chronic/recurrent (c/r)ENL. METHODS This cross-sectional study conducted over a period of 1 year included patients diagnosed as having leprosy relapse and those with c/rENL. Skin biopsy specimens were examined by conventional PCR for resistance testing for rifampicin, dapsone and ofloxacin, respectively targeting the rpoB, folP and gyrA genes of Mycobacterium leprae. RESULTS In total, 61 patients (25 smear-negative) were included in the study. Of these, 37 were diagnosed as having leprosy relapse and 24 as having c/rENL. Drug resistance to at least one drug was identified in 10 cases (16.4%). Rates of drug resistance were 5.4% (2 of 37) for dapsone, 10.8% (4 of 37) for rifampicin and 2.7% (1 of 37) for ofloxacin among cases of relapse, whereas it was 12.5% (3 of 24) and 8.3% (2 of 24) for dapsone and rifampicin respectively among those with c/rENL. Multidrug resistance was seen in 3.3% patients (2 of 61). CONCLUSION Drug-resistance rate among those with c/rENL was almost equalled that of relapse. Smear-negative leprosy relapse cases also had resistance to bactericidal drugs. These findings call for modifications in criteria for testing under leprosy drug-resistance surveillance and all cases of relapse and those with recalcitrant c/rENL should be tested.