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Journal of Clinical Microbiology, January 2001, p. 217-221, Vol. 39, No. 1
Departments of
Pathology1 and
Medicine,3 Baylor College of Medicine,
Houston, Texas 77030, and Laboratory of Human Bacterial
Pathogenesis, Rocky Mountain Laboratories, National Institute of
Allergy and Infectious Diseases, National Institutes of Health,
Hamilton, Montana 598402
Received 22 August 2000/Returned for modification 19 September
2000/Accepted 10 October 2000
Population-based analysis of Mycobacterium tuberculosis
transmission in Houston, Tex., over 5 years identified 377 patients infected with an isolate containing one to four copies of
IS6110. The isolates were analyzed by spoligotyping and
assigned to one of three major genetic groups based on nucleotide
polymorphisms in codons katG 463 and gyrA 95. Prospectively obtained patient interviews were reviewed to assess
epidemiologic links between apparently clustered patients. A total of
13 groups of isolates with the same IS6110 profile were
identified, representing 326 of the 377 patients (86.5%; range 2 to
113 patients). In contrast, 28 groups of isolates containing 334 patients (88.6%) had the same spoligotype (range, 2 to 143 patients).
Combination of IS6110 profile and spoligotype data
identified 31 clusters with 300 patients (79.6%; range, 2 to 82 patients). All 377 isolates belonged to major genetic group 1 (77 patients) or genetic group 2 (300 patients); no major genetic group 3 isolates were identified. Among the 228 patients interviewed, 33 patients (14.5%) were directly linked to another patient in the same
cluster. Possible epidemiologic links were also found among 11 patients. Moreover, many clusters consisted of individuals with the
same ethnicity. In conclusion, we confirmed that IS6110
profiling and spoligotyping together provide enhanced molecular
discrimination of M. tuberculosis isolates with low copy
numbers of IS6110. Identification of epidemiologic links
among some of the patients verified that the combination of these two
methods reliably indexes tuberculosis transmission.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.1.217-221.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Transmission Dynamics and Molecular
Characterization of Mycobacterium tuberculosis Isolates with
Low Copy Numbers of IS6110
*
Corresponding author. Mailing address: Department of
Pathology (209E), Baylor College of Medicine, One Baylor Plaza,
Houston, TX 77030-3498. Phone: (713) 798-8097. Fax: (713)
798-8895. E-mail: egraviss{at}bcm.tmc.edu.
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