Emergence of primary drug resistance to rifampicin in Mycobacterium leprae strains from leprosy patients in India.

Although the prevalence of leprosy has significantly decreased since the introduction of theWorld Health Organization (WHO) regimen of multidrug therapy (MDT), the incidence remains high, with a report of approximately 215 656 cases globally in 2013. Among these, 126 913 cases were reported from India alone [1]. Of a total number of 3196 relapse cases, India alone contributed 486 cases [1]. For most of the infectious diseases for which secondary prevention is provided by chemotherapy alone, the emergence of drug resistance ultimately becomes a concern and a threat to the intervention programmes. However, the fight against leprosy has been a great success, largely because of the development of MDT in 1981. The efficacy of MDT in curing leprosy during the last three decades has brought about a dramatic decline in the disease burden in all leprosy-endemic countries. The annual new case detection rate has also started to decline in some countries. In India, the prevalence of leprosy decreased from 4.2 per 10 000 population in 2002 to 0.68 per 10 000 population in 2014 [2]. At this stage of elimination (<1/10 000), any emergence of drug-resistant Mycobacterium leprae strains will greatly hamper the control programme of the country. Previous records reveal that, after almost 30 years of dapsone monotherapy, dapsone-resistant M. leprae was a major issue in the leprosy control programme [3]. As rifampicin is the main drug used in MDT and the only bactericidal drug, it is very important to follow the emergence