Preya Velji,1 Vladyslav Nikolayevskyy,1 Timothy Brown, and Francis Drobniewski
Author affiliations: Barts and The London School of Medicine, Queen Mary, University of London, London, UK (P. Velji, V. Nikolayevskyy); and Health Protection Agency National Mycobacterium Reference Laboratory, London (T. Brown, F. Drobniewski)
Suggested citation for this article
To address conflicting results about the stability of variable number tandem repeat (VNTR) loci and their value in prospective molecular epidemiology of Mycobacterium tuberculosis, we conducted a large prospective population-based analysis of all M. tuberculosis strains in a metropolitan setting. Optimal and reproducible conditions for reliable PCR and fragment analysis, comprising enzymes, denaturing conditions, and capillary temperature, were identified for a panel of hypervariable loci, including 3232, 2163a, 1982, and 4052. A total of 2,261 individual M. tuberculosis isolates and 265 sets of serial isolates were analyzed by using a standardized 15-loci VNTR panel, then an optimized hypervariable loci panel. The discriminative ability of loci varied substantially; locus VNTR 3232 varied the most, with 19 allelic variants and Hunter-Gaston index value of 0.909 unNN. Hypervariable loci should be included in standardized panels because they can provide consistent comparable results at multiple settings, provided the proposed conditions are adhered to.