OBJECTIVE: To study the stability and allelic diversity of tandem repeat loci in M. leprae in leprosy patients of Cebu, Philippines, and the suitability of multilocus variable number of tandem repeat (VNTR) analysis (MLVA) typing for detecting transmission.
METHODS: Seventy newly diagnosed leprosy patients consulting at the Leonard Wood Memorial, Cebu Skin Clinic Total DNA was extracted from slit skin smear (SSS) scrapings of each patient and used for amplification of 13 M. leprae VNTR loci by single locus or multiplex PCR. Number of repeats for each VNTR locus was obtained by DNA sequencing or fragment length analysis methods. Medical, social and geographic details were included in the molecular epidemiology database.
RESULTS AND CONCLUSIONS: Multiplex PCR (MP) and fragment length analysis (FLA) methods were found to be more efficient and accurate compared to single short tandem repeat (STR) amplification and DNA sequencing. Intra-patient MLVA patterns from four different samples were conserved in the minisatellites, while differences in one or more of the polymorphic and stutter prone microsatellites was observed, in four of five patients. The 13 loci could differentiate M. leprae strains in Cebu, however, MLVA patterns were stable enough during incubation and transmission between individuals within multi-case families. Thus M. leprae MLVA has potential for strain typing and transmission studies in Cebu.
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