Molecular Profiling of Drug Resistant Isolates of Mycobacterium tuberculosis in North India

Multidrug-resistant tuberculosis (MDR-TB) is a major public health problem because treatment is complicated, cure rates are well below those for drug susceptible tuberculosis (TB), and patients may remain infectious for months or years despite receiving the best available therapy. To gain a better understanding of MDR-TB, we characterized isolates recovered from 69 patients with MDR-TB, by use of IS6110 restriction fragment-length polymorphism (RFLP) analysis; spacer oligonucleotide genotyping (i.e. spoligotyping). Clinical isolates from patients with tuberculosis have been considered to contain clonally expanded Mycobacterium tuberculosis (MTB) strain. Over the years, the identification method based on IS6110 insertion sequences has been established as the standard for typing strains of MTB. IS6110 RFLP fingerprinting is very convincing when it is applied to classify MTB isolates harboring a large number of IS6110 in their chromosomes. Therefore, in the present study we have characterized the isolates from the patients suffering from MDR TB, on the basis of conserved Variable Number Tandem Repeats (VNTR), Direct Repeats (DR) and Insertion Sequences (IS) IS6110 elements. The polymorphic data showed significant level of dissimilarities among all the MDR isolates of MTB. Comparative studies with the DR and VNTR data substantiate that polymorphism occur among MDR-TB cases as shown by the number of repeats present in different clinical isolates.