Unearthing novel mutations and genetic variation in drug sensitive and resistant isolates of Mycobacterium tuberculosis through whole genome sequencing: A study from eastern Uttar Pradesh, India.

PURPOSE: Drug-resistant tuberculosis (DR-TB) presents a formidable public health challenge worldwide. Therefore, this study was conducted to elucidate the complete genetic profiles of drug-sensitive (DS), and drug-resistant TB isolates using Whole Genome Sequencing (WGS).

METHODS

The study includes a set of sputum specimens containing five DS-TB, multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) from distinct individuals. The identification and susceptibility was confirmed using GeneXpert assay, GenoType MTBDR plus assay, and GenoTypeMTBDRsl assay. Furthermore, specimens were cultured using the BD BACTEC MGIT 960 and subsequently confirmed through Capilia rapid kit. WGS was employed for the identification of Single Nucleotide Polymorphisms (SNPs), Mycobacterium tuberculosis complex (MTBC) lineages, and spoligotypes. The H37Rv was used as a positive control.

RESULTS

The findings of WGS showed, all the MDR-TB and XDR-TB isolates exhibited non-synonymous mutation (Ser450Leu, Gln432Leu, and His445Gln) within the rpoB gene. The isolates were simultaneously harboring mutations at fabG1-8T > C, fabG1-17G > T, fabG1-15C > T, and inhA-154G > A. One DS-TB isolate was carrying resistance mutations in the rrs gene at position 517C > T, while three MDR-TB isolates turned out to be pre-XDR-TB carrying mutations associated with fluoroquinolone (FQ) resistance (gyrA Ala90Val, gyrA Asp94His, and gyrA Asp94 Gly). The study reports novel mutations pncA391dupG and for the first time mutation in thyX gene in clinical isolates of MTBC. Most of the MDR/XDR-TB isolates were predominantly associated with the Beijing sub-lineage within the East Asian Lineage 2.

CONCLUSIONS

In conclusion, our study highlighted the challenges surrounding the rapid identification and essential information regarding the genetic diversity of TB strains which contribute valuable insights into the TB epidemiology.