Detection of Resistant Prevalent Genes for Mycobacterium Tuberculosis by Line Probe Assay

A BSTRACT Background: The emergence of drug-resistant Mycobacterium tuberculosis (Mtb) strains especially MDR-TB and indeed XDR-TB is a real threat to achieving TB control. Rapid diagnosis of mutations in drug-resistant strains has vital importance in the prognosis. The aim was to identify mutations responsible for drug resistance in Mtb strains derived from patients with tuberculosis using the line probe assay (LPA) method. Materials and Methods: Samples from 191 pulmonary and extrapulmonary Mtb-positive patients by GeneXpert-CBNAAT were collected in 50 ml sterile Falcon tube from MDR-TB suspects. Specimens were decontaminated, and the LPA test was done. Band pattern analysis of LPA strips was performed as per manufacturer’s instructions. Results: Out of total samples, 24 (12.6%) were rifampicin resistant on GeneXpert-CBNAAT. Samples resistant to first line drugs were 31 (16%); among them, 19 were MDR-TB. In 86.36% of specimens, mutation in rpoB gene was at 531-533 codons and Ser531Leu mutation. A total 96% of specimen resistant to isoniazide were high-level resistance, diagnosed by mutation in katG gene. In katG gene, 68% of mutants have S315T1 mutation and 32% have hybrid, i.e., S315T1 and S315T2 mutation. In inhA gene, hybrid mutation at -8 and -15, -16, i.e., C15T and A16G mutations were seen. Out of 31 specimens resistant to first-line drugs, 8 (25%) were resistant to second-line drugs. Most common mutations seen in gyrA and rrs genes were D94N/Y and A1401G, respectively. Conclusion: Rifampicin resistance appears to be an effective marker of MDRTB. Mutation pattern of resistant genes in MTB positive specimens was in line with the literature.