Characterisation of Short tandem repeats for genotyping Mycobacterium leprae

Objective: Establish a typing system for Mycobacterium leprae based on polymorphic DNA structures known as short tandem repeats (STR). Design: Assess 16 polymorphic STR for sensitivity, specificity and reproducibility in standard assays using reference strains of M. leprae. Results: Primers for 16 STR loci were selected based on PCR product size and for their ability to sequence each STR locus from both directions. All primer pairs produced a visible PCR amplicon of appropriate size from PCR reactions containing 10 M. leprae cells. DNA sequences for each STR locus, except (AT)15, was correctly identified as M. leprae-specific in replicate samples containing 1000 M. leprae using either the forward or reverse PCR primers. Twelve of 13 M. leprae STR loci were stable during passage in heavily infected armadillo tissues over a 5 year and 7 month infection cycle. Conclusions: Certain M. leprae STR provide suitable targets for strain typing with the potential for grouping M. leprae with shared genotypes that may prove useful for establishing linkages between leprosy cases within geographical regions