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Journal of Clinical Microbiology, March 2000, p. 1231-1234, Vol. 38, No. 3
Unité de la Tuberculose et des
Mycobactéries, Institut Pasteur, F-97165 Pointe à Pitre
Cedex, Guadeloupe
Received 28 September 1999/Accepted 8 December 1999
Spoligotyping, a method based on the variability of distribution of
the 43 inter-direct repeat (DR) spacers of Mycobacterium tuberculosis and Mycobacterium bovis BCG, is useful
to study the molecular epidemiology of bovine and human tuberculosis.
Recently, a major family of M. tuberculosis clinical
isolates named the Haarlem family, which did not contain spacers 31 and
33 to 36, was reported in a multicenter study. Independently, a data
bank containing all the published spoligotypes showed that the two most
prevalent spoligotypes in the world differed only by the presence or
absence of spacer 31. A careful analysis of the DR locus sequence led
us to hypothesize that spacer 31 may not have been amplified in some
isolates with the primer sets DRa and DRb currently used for
spoligotyping. Consequently, a modified spoligotyping method based on
different combinations of the 36-bp DR and IS6110 primers
was devised that was able to discriminate between the left and the
right parts of the DR locus and demonstrated the presence of the
previously unamplified spacer 31 for some of the clinical isolates. By
analogy, we suggest that a single-spacer difference in some
epidemiologically linked cases of tuberculosis may simply arise due to
the insertion of an extra copy of IS6110 within the DR
locus, leading to its asymmetrical disruption and subsequent lack of
the DRa or DRb targets. The influence of the IS6110
preferential insertion sites within the DR locus on spoligotyping results should be further investigated.
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Detection of a Previously Unamplified Spacer
within the DR Locus of Mycobacterium tuberculosis:
Epidemiological Implications
*
Corresponding author. Mailing address: Unité de
la Tuberculose et des Mycobactéries, Institut Pasteur, Morne
Jolivière, BP 484, F-97165 Pointe-à-Pitre Cedex,
Guadeloupe. Phone: 590-893-881. Fax: 590-893-880. E-mail:
rastogi{at}ipagua.gp.
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