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Journal of Clinical Microbiology, June 2001, p. 2083-2088, Vol. 39, No. 6
Molecular Biology Research Department,
Laboratory Research Branch, National Hansen's Disease Programs at the
School of Veterinary Medicine, Louisiana State University, Baton Rouge,
Louisiana,1 and Leprosy Research Center,
National Institute of Infectious Diseases, Tokyo,
Japan2
Received 12 October 2000/Returned for modification 20 November
2000/Accepted 22 March 2001
Currently recommended control measures for treating leprosy with
multidrug therapy should control the spread of drug-resistant strains;
however, dapsone (DDS) resistance continues to be reported. Comprehensive estimates of drug-resistant leprosy are difficult to
obtain due to the cumbersome nature of the conventional drug susceptibility testing method using mouse footpad inoculation, which
requires at least 6 months to obtain results. Recently, it has been
determined that DDS-resistant strains contain missense mutations in
codon 53 or 55 of the folP1 gene of Mycobacterium leprae, and definitive evidence linking these mutations with DDS resistance in M. leprae has been obtained. Based on these
mutations, a heteroduplex DDS M. leprae (HD-DDS-ML) assay
was developed for the simultaneous detection of M. leprae
and of its susceptibility to DDS. The assay relies on the PCR
amplification of an M. leprae-specific 231-bp fragment of
folP1 containing codons 53 and 55. The PCR products are
allowed to anneal to a universal heteroduplex generator, and the
separation of the resultant DNA duplexes is accomplished by
polyacrylamide gel electrophoresis. M. leprae was detected in crude cell lysates of skin biopsy specimen homogenates from eight
leprosy patients and from M. leprae-infected mouse or
armadillo tissues infected with 14 separate strains using the HD-DDS-ML assay. The assay was specific for M. leprae in a comparison
with results obtained from 14 species of mycobacteria other than
M. leprae and four bacterial species known to colonize
human skin. The HD-DDS-ML assay detected as few as 100 M. leprae organisms present in homogenates of human skin and
demonstrated a 93% correlation with DDS susceptibility as determined
by both DNA sequencing of folP1 and mouse footpad
susceptibility testing. The HD-DDS-ML assay provides a new tool for the
simultaneous detection of M. leprae and of its
susceptibility to DDS from a single specimen. The assay should prove
useful for drug resistance surveillance in leprosy control programs
when combined with similar molecular tests developed for other drug
resistance markers.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.6.2083-2088.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Simultaneous Detection of Mycobacterium
leprae and Its Susceptibility to Dapsone Using DNA
Heteroduplex Analysis
*
Corresponding author. Mailing address: Molecular
Biology Research Dept., Laboratory Research Branch, National Hansen's
Disease Programs at the School of Veterinary Medicine, Louisiana State University, P.O. Box 25072, Baton Rouge, LA 70894. Phone: (225) 578-9839. Fax: (225) 578-9856. E-mail: dwill21{at}lsu.edu.
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