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Journal of Clinical Microbiology, April 2001, p. 1595-1599, Vol. 39, No. 4
Unité de la Tuberculose et des
Mycobactéries, Institut Pasteur de Guadeloupe, 97165 Pointe-à-Pitre Cedex, Guadeloupe
Received 12 October 2000/Returned for modification 19 December
2000/Accepted 30 January 2001
Based on the variability of 43 spacers within the direct repeat
(DR) locus of Mycobacterium tuberculosis complex organisms, spoligotyping is a rapid method that aids in the study of the epidemiology of tuberculosis. It was recently hypothesized that despite
its presence in the DR locus, spacer 31 could not be amplified in
M. tuberculosis clinical isolates belonging to spoligotype 50 due to the insertion of an extra copy of IS6110 between
spacers 31 and 32 that could lead to an asymmetrical split of the
primer targets (I. Filliol, C. Sola, and N. Rastogi, J. Clin.
Microbiol. 38:1231-1234, 2000). In the present investigation, previous
observations were extended to 25 clinical isolates of type 50 showing
that the primer set IS6-DRb that selectively amplified the left and central DR regions was indeed able to demonstrate the presence of
spacer 31. IS6110-restriction fragment length polymorphism (RFLP) and DR-RFLP showed that type 50 isolates were characterized by
the presence of two copies of IS6110 associated with the DR locus and an additional double IS6110 band of 1.4 kb. The
primer set IS3-IS6 was then used to selectively amplify a 750-bp
inter-IS6110 fragment within the DR locus. The sequencing
of the central DR region corroborated our previous findings and showed
that the absence of spacer 31 among the type 50 isolates was due to the asymmetric insertion of an extra copy of IS6110 between
spacers 31 and 32, leading to an unequal split of the DRa-DRb target
into two portions, of 6 and 30 bp, respectively. These results show that the DR locus constitutes an ideal IS6110 preferential
locus (ipl), permitting the insertion of two or more copies
of IS6110, and provide new clues for epidemiological and
phylogenetic interpretation of changes in IS6110-RFLP and
spoligotyping profiles.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.4.1595-1599.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Use of Spoligotyping To Study the Evolution of the
Direct Repeat Locus by IS6110 Transposition in
Mycobacterium tuberculosis
*
Corresponding author. Mailing address: Unité de
la Tuberculose et des Mycobactéries, Institut Pasteur de
Guadeloupe, Morne Jolivière, BP 484, F-97165 Pointe-à-Pitre
Cedex, Guadeloupe. Phone: 590-893-881. Fax: 590-893-880. E-mail:
rastogi{at}pasteur.gp.
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