Molecular typing of Mycobacterium leprae

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DESCRIPTION (PROVIDED BY APPLICANT): An objective of the 1991 World Health Assembly was the elimination of leprosy as a public health problem by the year 2000. The goal was to achieve a reduction in prevalence of leprosy to less than 1 per 10,000 population. This goal has not been achieved in the most endemic countries, where more than 80% of the global leprosy cases occur, despite the implementation of the Multi Drug Therapy (MDT) program. The number of new cases detected has also not reduced indicating that the transmission of the causative agent Mycobacterium leprae has not been controlled. There are fundamental gaps in the understanding of transmission, and a lack of sensitive methods to track leprosy. Questions remain regarding the nature of the reservoir of M. leprae, the route of infection, and mode of its spread. To address these concerns, a DNA typing method for M. leprae is proposed based on the availability of the genome sequence and the principle of multiple locus variable-number of tandem repeat analysis (MLVA), which has been developed for several other infectious organisms. M. leprae cannot be cultivated in a laboratory and bacteria for research applications is mainly derived from susceptible armadillo or nude mice. This pilot study is therefore designed with two specific aims: 1. Development of a standard molecular typing method using a panel of armadillo derived M. leprae isolates and 2. Application of the optimized methods in a panel of M. leprae DNA derived from biopsies and nasal swabs from patients. The methods involve the PCR amplification of multiple genomic loci containing short tandem repeats for each isolate of M. leprae and the comparison of the fragment length of each locus with that obtained from other isolates. Automated electrophoresis, data collection and analysis will be used. The long-term goal of the study is to provide the tools and techniques suitable for future epidemiological studies such as the role of human, non-human and environmental sources of M. leprae in the transmission of leprosy via nasal or dermal routes of ntry and release of the pathogen and the differentiation of relapse from reinfection in patients.