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Volume 15, Number 10—October 2009


Discriminatory Ability of Hypervariable Variable Number Tandem Repeat Loci in Population-based Analysis of Mycobacterium tuberculosis Strains, London, UK

Preya Velji1, Vladyslav Nikolayevskyy1, Timothy Brown, and Francis DrobniewskiComments to Author 
Author affiliations: Barts and The London School of Medicine, Queen Mary, University of London, London, UK (P. Velji, V. Nikolayevskyy); Health Protection Agency National Mycobacterium Reference Laboratory, London (T. Brown, F. Drobniewski); 1These authors contributed equally to this article.

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Table 3

Discriminatory power of VNTR typing used in the study in establishing true minimum cluster size as marker of real transmission rate*

Genotyping method No. distinct profiles (variety of types) No. clusters Size of clusters, no. isolates Clustering rate, % (n/N) Recent transmission rate, % ([n – c]/N) No. unique isolates
MIRU15 (n = 2261) 1,271 235 2–53 54.2 44.0 1,036
MIRU15 + Spoligotyping 1,619 196 2–48 37.1 29.0 1,423
MIRU15 + VNTR7 1,888 158 2–35 22.2 17.0 1,730

*MIRU, mycobacterial interspersed repetitive unit; VNTR, variable number tandem repeats; n, no. clustered cases; N, total no. of strains; c, no. of clusters.

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