Microsatellite typing of Mycobacterium leprae strains in newly diagnosed multibacillary leprosy patients to trace out the transmission pattern

Abstract

Background: Leprosy was eliminated from India in December 2005 imprinting a prevalence rate of <1/10,000 population. Still some endemic pockets exist in India where the new cases of leprosy continue to occur at a constant rate. It means the active transmission of leprosy is still continuing. In the present study, we aimed to elucidate the transmission pattern of Mycobacterium leprae using three microsatellite loci. Methods: Slit-skin samples from 36 newly diagnosed multi-bacillary leprosy cases from Ghatampur, Kanpur Nagar, Uttar Pradesh, India, were collected in a sterile centrifuge tube containing Tris-EDTA (TE) buffer. DNA was isolated, and the microsatellite loci, namely, (GT)6, (TA)18, and (TA)8CA3 were amplified using the in-house designed primers. The amplified products were recovered through polymerase chain reaction cleanup kit and sequenced by Sangers method in a 16 capillary genetic analyzer. Results: Sequences were searched by Basic Local Alignment Search Tool, and phylogenetic analysis was done to trace out the transmission pattern of M. leprae. Out of the three microsatellite loci, (TA)18 was unable to define the transmission pattern while (GT)6 and (TA)8CA3 were endowed with distinct signature for transmission of M. leprae in the study segment of the population. Conclusions: We found that nine types of M. leprae strains were circulating in the Ghatampur area and the same type of strains were found in the same villages or in neighboring villages. To conclude the study, we accentuated that (TA)8CA3 is a better microsatellite locus for strain typing of M. leprae.