Mycobacterium tuberculosis Typing: A Molecular Epidemiologic Tool to Control and Manage Tuberculosis

Mycobacterium tuberculosis (M. tuberculosis), the causative agent of tuberculosis is still a major health threatening problem worldwide. It is considered as the top infectious killer, with a figure of 4500 lives a day, all over the world. According to the CDC report, in 2016, 10.4 million people had tuberculosis of which 1.7 million died. By the emergence of MDR and XDR strains of M. tuberculosis, even the treatment and control of the disease have been more sophisticated.Molecular typing of M. tuberculosis has been widely used for different epidemiologic purposes, including outbreak studies, misdiagnosis and mixed infections detections, identifications of strain lineage, and their correlations with drug resistance, and discrimination of the related strains from un-related ones, to name a few. The data obtained from typing of the bacteria can potentially be used to control, manage and monitor the disease. Among the several techniques proposed for typing of Mycobacterium, the method of choice is based on different geographical conditions and the laboratory facilities. Although restriction fragment length polymorphism (RFLP) is considered the gold standard method of M.tuberculosis typing, because of its limitations, other methods have often been replaced. Spacer oligonucleotide typing (Spoligotyping), variable number of tandem repeats (VNTR), mycobacterial interspersed repetitive units-variable number tandem repeats (MIRU-VNTR), whole genome sequencing (WGS), MLST (multilocus sequence typing) and several alternative methods are the other typing procedures, frequently used. Spoligotyping is more sensitive than RFLP and the demanded DNA for the former is less than that used in RFLP. Spoligotyping might be the technique of choice in screening test followed by other methods of typing.