Molecular typing based on 12 loci containing variable numbers of tandem repeats of mycobacterial interspersed repetitive units (MIRU-VNTRs) has been adopted in combination with spoligotyping as the basis for large-scale, high-throughput genotyping of Mycobacterium tuberculosis. However, even the combination of these two methods is still less discriminatory than IS6110 fingerprinting. Here, we define an optimized set of MIRU-VNTR loci with a significantly higher discriminatory power. The resolution and the stability/robustness of 29 loci were analyzed, using a total of 824 tubercle bacillus isolates, including representatives of the main lineages identified worldwide so far. Five loci were excluded for lack of robustness and/or stability in serial isolates or isolates from epidemiologically linked patients. The use of the 24 remaining loci increased the number of types by 40%-and by 23% in combination with spoligotyping-among isolates from cosmopolitan origins, compared to those obtained with the original set of 12 loci. Consequently, the clustering rate was decreased by fourfold-by threefold in combination with spoligotyping-under the same conditions. A discriminatory subset of 15 loci with the highest evolutionary rates was then defined that concentrated 96% of the total resolution obtained with the full 24-locus set. Its predictive value for evaluating M. tuberculosis transmission was found to be equal to that of IS6110 restriction fragment length polymorphism typing, as shown in a companion population-based study. This 15-locus system is therefore proposed as the new standard for routine epidemiological discrimination of M. tuberculosis isolates and the 24-locus system as a high-resolution tool for phylogenetic studies.The genotyping of Mycobacterium tuberculosis isolates contributes to tuberculosis (TB) control by, e.g., indicating possible epidemiological links between TB patients, detecting (un)suspected outbreaks and laboratory cross-contamination, and distinguishing exogenous reinfection from endogenous reactivation in relapse cases. For these purposes, IS6110 restriction fragment length polymorphism (RFLP) typing (48) has been used as the gold standard method for more than a decade. However, this method is labor-intensive, requires weeks for culturing the isolates and subsequent DNA purification, and suffers from problems of interpretability and portability of the complex banding patterns. In addition, it provides insufficient discrimination among isolates with low (Ͻ6) IS6110 copy numbers, a problem that is only partly overcome by using PCR-based spoligotyping as a secondary method (6).Genotyping based on variable numbers of tandem repeats (VNTRs) of different classes of interspersed genetic elements named mycobacterial interspersed repetitive units (MIRUs) (12,25,32,36,40,43,44) is increasingly used to solve these problems. This method relies on PCR amplification of multiple loci using primers specific for the flanking regions of each repeat locus and on the determination of the sizes of the amplicons...

New therapeutic strategies are needed to combat the tuberculosis pandemic and the spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) forms of the disease, which remain a serious public health challenge worldwide. The most urgent clinical need is to discover potent agents capable of reducing the duration of MDR and XDR tuberculosis therapy with a success rate comparable to that of current therapies for drug-susceptible tuberculosis. The last decade has seen the discovery of new agent classes for the management of tuberculosis, several of which are currently in clinical trials. However, given the high attrition rate of drug candidates during clinical development and the emergence of drug resistance, the discovery of additional clinical candidates is clearly needed. Here, we report on a promising class of imidazopyridine amide (IPA) compounds that block Mycobacterium tuberculosis growth by targeting the respiratory cytochrome bc1 complex. The optimized IPA compound Q203 inhibited the growth of MDR and XDR M. tuberculosis clinical isolates in culture broth medium in the low nanomolar range and was efficacious in a mouse model of tuberculosis at a dose less than 1 mg per kg body weight, which highlights the potency of this compound. In addition, Q203 displays pharmacokinetic and safety profiles compatible with once-daily dosing. Together, our data indicate that Q203 is a promising new clinical candidate for the treatment of tuberculosis.

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Strains of the Beijing/W genotype family of Mycobacterium tuberculosis have caused large outbreaks of tuberculosis, sometimes involving multidrug resistance. This genetically highly conserved family of M. tuberculosis strains predominates in some geographic areas. We have conducted a systematic review of the published reports on these strains to determine their worldwide distribution, spread, and association with drug resistance. Sixteen studies reported prevalence of Beijing strains defined by spoligotyping; another 10 used other definitions. Beijing strains were most prevalent in Asia but were found worldwide. Associations with drug resistance varied: in New York, Cuba, Estonia, and Vietnam, Beijing strains were strongly associated with drug resistance, but elsewhere the association was weak or absent. Although few reports have measured trends in prevalence, the ubiquity of the Beijing strains and their frequent association with outbreaks and drug resistance underline their importance.